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Du Z, Li Z, Liu M, Sun M, Ma X, Wang L, Kang Z, Zhao J. Virulence and Molecular Characterization Reveal Signs of Sexual Genetic Recombination of Puccinia striiformis f. sp. tritici and Puccinia striiformis f. sp. hordei in Tibet. PLANT DISEASE 2024; 108:2341-2353. [PMID: 38268170 DOI: 10.1094/pdis-05-23-0852-re] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2024]
Abstract
Stripe rust of wheat and barley is caused by different formae speciales, Puccinia striiformis f. sp. tritici (Pst) and P. striiformis f. sp. hordei (Psh), respectively. To understand the relationship between the populations of the two formae speciales, a total of 260 P. striiformis isolates, including 140 from barley and 120 from wheat collected from Linzhi, Tibet, China, from 2018 to 2020, were tested on 18 barley and 13 wheat genotypes and genotyped with 26 single-nucleotide polymorphism (SNP)-based Kompetitive allele-specific PCR (KASP) markers. As a result, 260 isolates were identified as 83 virulence phenotypes (VPs), 115 of which as 9 VPs and could infect only wheat (wheat population), 111 as 54 VPs and could infect only barley (barley population), and 34 belonged to 20 VPs that could infect both wheat and barley (mixed population). Of the 149 multilocus genotypes (MLGs) that were identified, 92 were from wheat, 56 from barley, and 1 from both wheat and barley. Phenotypic and genotypic diversity was high in the populations from wheat and barley. Low linkage disequilibrium was found in most of the sampling sites of both crops, indicating strong signs of sexual reproduction (|r̄d| = 0.022 to 0.393, P = 0.004 to 0.847), whereas it was not observed in the overall population (wheat and barley sources) and the wheat, barley, and mixed populations, which may be because of the complex composition of isolates. Population structure analyses based on phenotyping and SNP-KASP genotypes supported the separation of the two formae speciales. However, MLGs and clusters containing isolates from both wheat and barley obviously indicated sexual genetic recombination between the two formae speciales. The results of the study provided an insight into evolution of Pst and Psh and showed the importance of management strategies for stripe rust of wheat and barley in regions where both crops are grown.
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Affiliation(s)
- Zhimin Du
- State Key Laboratory for Crop Stress Resistance and High-Efficiency Production, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Zejian Li
- State Key Laboratory for Crop Stress Resistance and High-Efficiency Production, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Maxinzhi Liu
- State Key Laboratory for Crop Stress Resistance and High-Efficiency Production, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Mudi Sun
- State Key Laboratory for Crop Stress Resistance and High-Efficiency Production, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Xinyao Ma
- State Key Laboratory for Crop Stress Resistance and High-Efficiency Production, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Lin Wang
- State Key Laboratory for Crop Stress Resistance and High-Efficiency Production, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Zhensheng Kang
- State Key Laboratory for Crop Stress Resistance and High-Efficiency Production, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Jie Zhao
- State Key Laboratory for Crop Stress Resistance and High-Efficiency Production, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China
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Alassimone J, Praz C, Lorrain C, De Francesco A, Carrasco-López C, Faino L, Shen Z, Meile L, Sánchez-Vallet A. The Zymoseptoria tritici Avirulence Factor AvrStb6 Accumulates in Hyphae Close to Stomata and Triggers a Wheat Defense Response Hindering Fungal Penetration. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2024; 37:432-444. [PMID: 38265007 DOI: 10.1094/mpmi-11-23-0181-r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2024]
Abstract
Zymoseptoria tritici, the causal agent of Septoria tritici blotch, is one of Europe's most damaging wheat pathogens, causing significant economic losses. Genetic resistance is a common strategy to control the disease, Stb6 being a resistance gene used for more than 100 years in Europe. This study investigates the molecular mechanisms underlying Stb6-mediated resistance. Utilizing confocal microscopy imaging, we determined that Z. tritici epiphytic hyphae mainly accumulate the corresponding avirulence factor AvrStb6 in close proximity to stomata. Consequently, the progression of AvrStb6-expressing avirulent strains is hampered during penetration. The fungal growth inhibition co-occurs with a transcriptional reprogramming in wheat characterized by an induction of immune responses, genes involved in stomatal regulation, and cell wall-related genes. Overall, we shed light on the gene-for-gene resistance mechanisms in the wheat-Z. tritici pathosystem at the cytological and transcriptomic level, and our results highlight that stomatal penetration is a critical process for pathogenicity and resistance. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.
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Affiliation(s)
- Julien Alassimone
- Plant Pathology, Institute of Integrative Biology, ETH Zürich, Zürich, Switzerland
| | - Coraline Praz
- Centro de Biotecnología y Genómica de Plantas (CBGP)/Universidad Politécnica de Madrid-Instituto Nacional de Investigación Agraria y Alimentaria/Centro Superior de Investigaciones Científicas (INIA/CSIC), Campus de Montegancedo, Pozuelo de Alarcón (Madrid), Spain
| | - Cécile Lorrain
- Plant Pathology, Institute of Integrative Biology, ETH Zürich, Zürich, Switzerland
| | - Agustina De Francesco
- Centro de Biotecnología y Genómica de Plantas (CBGP)/Universidad Politécnica de Madrid-Instituto Nacional de Investigación Agraria y Alimentaria/Centro Superior de Investigaciones Científicas (INIA/CSIC), Campus de Montegancedo, Pozuelo de Alarcón (Madrid), Spain
| | - Cristian Carrasco-López
- Centro de Biotecnología y Genómica de Plantas (CBGP)/Universidad Politécnica de Madrid-Instituto Nacional de Investigación Agraria y Alimentaria/Centro Superior de Investigaciones Científicas (INIA/CSIC), Campus de Montegancedo, Pozuelo de Alarcón (Madrid), Spain
| | - Luigi Faino
- Environmental Biology, Sapienza University of Rome, Roma, Italy
| | - Ziqi Shen
- Plant Pathology, Institute of Integrative Biology, ETH Zürich, Zürich, Switzerland
| | - Lukas Meile
- Centro de Biotecnología y Genómica de Plantas (CBGP)/Universidad Politécnica de Madrid-Instituto Nacional de Investigación Agraria y Alimentaria/Centro Superior de Investigaciones Científicas (INIA/CSIC), Campus de Montegancedo, Pozuelo de Alarcón (Madrid), Spain
| | - Andrea Sánchez-Vallet
- Plant Pathology, Institute of Integrative Biology, ETH Zürich, Zürich, Switzerland
- Centro de Biotecnología y Genómica de Plantas (CBGP)/Universidad Politécnica de Madrid-Instituto Nacional de Investigación Agraria y Alimentaria/Centro Superior de Investigaciones Científicas (INIA/CSIC), Campus de Montegancedo, Pozuelo de Alarcón (Madrid), Spain
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Ababa G. Biology, taxonomy, genetics, and management of Zymoseptoria tritici: the causal agent of wheat leaf blotch. Mycology 2023; 14:292-315. [PMID: 38187886 PMCID: PMC10769150 DOI: 10.1080/21501203.2023.2241492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Accepted: 07/22/2023] [Indexed: 01/09/2024] Open
Abstract
Septoria tritici blotch or Septoria leaf blotch has been used for long time, but leaf blotch is a correct disease name. Moreover, Lb resistant gene is the correct name, but, not Stb gene. It has sexual and asexual parts on the mycelia, known as heterothallic fungi. Its pathogenic diversity ranged from 40% to 93% and has produced a wide variety of AvrLb6 haplotypes. M. graminicola has a plasmogamy and karyogamy sexual process. The pathogen can use macropycnidiospores, micropycnidiospores, and pycnidia vegetative growths for infection and overwintering. Synthetic M3, Kavkaz-K4500, Synthetic 6×, and TE9111 wheat genotypes have horizontal resistance. Avirulence (Avr) genes in Z. tritici and their matching wheat (R) genes indicate gene for gene mechanisms of resistance. Twenty-two R genes (vertical resistance) have been identified. In both horizontal and vertical resistance, different Lb genes have been broken down due to new Z.tritici virulent gene and currently Lb19 resistant gene is being recommended. Mixing of resistant and susceptible cultivars is also the most effective management strategy. Moreover, different cultural practices and biological control have been proposed. Lastly, different fungicides are also available. However, in developing countries cultivar mixture, isolates diversity, biological control, and epidemic studies have been greatly missed.
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Affiliation(s)
- Girma Ababa
- Department of Plant Protection (Plant Pathology), Holetta Agricultural Research Center (HARC), Ethiopian Institute of Agricultural Research (EIAR), Holetta, Addis Ababa, Ethiopia
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Francisco CS, McDonald BA, Palma-Guerrero J. A transcription factor and a phosphatase regulate temperature-dependent morphogenesis in the fungal plant pathogen Zymoseptoria tritici. Fungal Genet Biol 2023; 167:103811. [PMID: 37196910 DOI: 10.1016/j.fgb.2023.103811] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2023] [Revised: 04/26/2023] [Accepted: 05/10/2023] [Indexed: 05/19/2023]
Abstract
Naturally fluctuating temperatures provide a constant environmental stress that requires adaptation. Some fungal pathogens respond to heat stress by producing new morphotypes that maximize their overall fitness. The fungal wheat pathogen Zymoseptoria tritici responds to heat stress by switching from its yeast-like blastospore form to hyphae or chlamydospores. The regulatory mechanisms underlying this switch are unknown. Here, we demonstrate that a differential heat stress response is ubiquitous in Z. tritici populations around the world. We used QTL mapping to identify a single locus associated with the temperature-dependent morphogenesis and we found two genes, the transcription factor ZtMsr1 and the protein phosphatase ZtYvh1, regulating this mechanism. We find that ZtMsr1 regulates repression of hyphal growth and induces chlamydospore formation whereas ZtYvh1 is required for hyphal growth. We next showed that chlamydospore formation is a response to the intracellular osmotic stress generated by the heat stress. This intracellular stress stimulates the cell wall integrity (CWI) and high-osmolarity glycerol (HOG) MAPK pathways resulting in hyphal growth. If cell wall integrity is compromised, however, ZtMsr1 represses the hyphal development program and may induce the chlamydospore-inducing genes as a stress-response survival strategy. Taken together, these results suggest a novel mechanism through which morphological transitions are orchestrated in Z. tritici - a mechanism that may also be present in other pleomorphic fungi.
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Affiliation(s)
| | - Bruce A McDonald
- Plant Pathology Group, Institute of Integrative Biology, 8092 ETH Zürich, Switzerland
| | - Javier Palma-Guerrero
- Plant Pathology Group, Institute of Integrative Biology, 8092 ETH Zürich, Switzerland.
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Du Z, Peng Y, Zhang G, Chen L, Jiang S, Kang Z, Zhao J. Direct Evidence Demonstrates that Puccinia striiformis f. sp. tritici Infects Susceptible Barberry to Complete Sexual Cycle in Autumn. PLANT DISEASE 2023; 107:771-783. [PMID: 35939748 DOI: 10.1094/pdis-08-22-1750-re] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Wheat stripe rust is an airborne and destructive disease caused by a heteroecious rust fungus Puccinia striiformis f. sp. tritici (Pst). Studies have demonstrated that the rust pathogen accomplishes sexual reproduction on susceptible barberry under natural conditions in spring, whereas Pst infection on barberry is still in blank in other seasons. In late October 2016, aecial production on barberry shrubs were observed in Linzhi, Tibet, China. Therefore, experimental tests were conducted to verify the existence of sexual cycles of Pst in this season. By inoculating 52 aecial clusters from 30 rusted barberry leaves, four Pst samples, T1 to T4, were successfully recovered from the rusted barberry shrubs. Sixty-five single uredinium (SU) isolates were derived from the four Pst samples. Based on virulence tests on the Chinese differential hosts, T1 to T4 samples were unknown races and showed mixed reactions on some differentials. Twenty-one known races and 44 unknown races belonging to five race groups were identified among the 65 SU isolates. Meanwhile, the 65 SU isolates produced 26 various virulence patterns (VPs; called VP1-VP26) on 25 single Yr gene lines and 15 multilocus genotypes (MLGs) at nine simple sequence repeat marker loci. Clustering analysis showed similar lineage among subpopulations and different lineage between subpopulations. Linkage disequilibrium analysis indicated that the SU population was produced sexually. This study first reported that Pst infects susceptible barberry to complete sexual reproduction in autumn. The results update the knowledge of disease cycle and management of wheat stripe rust and contribute to the understanding of rust genetic diversity in Tibet.
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Affiliation(s)
- Zhimin Du
- State Key Laboratory of Crop Stress Biology for Arid Areas, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Yuelin Peng
- Department of Plant Sciences, Agricultural and Animal Husbandry College of Tibet University, Linzhi, Tibet 86000, China
| | - Gensheng Zhang
- State Key Laboratory of Crop Stress Biology for Arid Areas, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Li Chen
- Extension Center for Agricultural Technology, Agriculture Department of Tibetan Autonomous Region, Tibet, China
| | - Shuchang Jiang
- State Key Laboratory of Crop Stress Biology for Arid Areas, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Zhensheng Kang
- State Key Laboratory of Crop Stress Biology for Arid Areas, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Jie Zhao
- State Key Laboratory of Crop Stress Biology for Arid Areas, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China
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Chen H, King R, Smith D, Bayon C, Ashfield T, Torriani S, Kanyuka K, Hammond-Kosack K, Bieri S, Rudd J. Combined pangenomics and transcriptomics reveals core and redundant virulence processes in a rapidly evolving fungal plant pathogen. BMC Biol 2023; 21:24. [PMID: 36747219 PMCID: PMC9903594 DOI: 10.1186/s12915-023-01520-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Accepted: 01/19/2023] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND Studying genomic variation in rapidly evolving pathogens potentially enables identification of genes supporting their "core biology", being present, functional and expressed by all strains or "flexible biology", varying between strains. Genes supporting flexible biology may be considered to be "accessory", whilst the "core" gene set is likely to be important for common features of a pathogen species biology, including virulence on all host genotypes. The wheat-pathogenic fungus Zymoseptoria tritici represents one of the most rapidly evolving threats to global food security and was the focus of this study. RESULTS We constructed a pangenome of 18 European field isolates, with 12 also subjected to RNAseq transcription profiling during infection. Combining this data, we predicted a "core" gene set comprising 9807 sequences which were (1) present in all isolates, (2) lacking inactivating polymorphisms and (3) expressed by all isolates. A large accessory genome, consisting of 45% of the total genes, was also defined. We classified genetic and genomic polymorphism at both chromosomal and individual gene scales. Proteins required for essential functions including virulence had lower-than average sequence variability amongst core genes. Both core and accessory genomes encoded many small, secreted candidate effector proteins that likely interact with plant immunity. Viral vector-mediated transient in planta overexpression of 88 candidates failed to identify any which induced leaf necrosis characteristic of disease. However, functional complementation of a non-pathogenic deletion mutant lacking five core genes demonstrated that full virulence was restored by re-introduction of the single gene exhibiting least sequence polymorphism and highest expression. CONCLUSIONS These data support the combined use of pangenomics and transcriptomics for defining genes which represent core, and potentially exploitable, weaknesses in rapidly evolving pathogens.
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Affiliation(s)
- Hongxin Chen
- grid.418374.d0000 0001 2227 9389Department of Protecting Crops and the Environment, Rothamsted Research, Harpenden, Herts UK ,grid.12981.330000 0001 2360 039XPresent address: School of Agriculture, Shenzhen Campus of Sun Yat-sen University, Guangming District, Shenzhen, Guangdong People’s Republic of China
| | - Robert King
- grid.418374.d0000 0001 2227 9389Department of Protecting Crops and the Environment, Rothamsted Research, Harpenden, Herts UK
| | - Dan Smith
- grid.418374.d0000 0001 2227 9389Department of Protecting Crops and the Environment, Rothamsted Research, Harpenden, Herts UK
| | - Carlos Bayon
- grid.418374.d0000 0001 2227 9389Department of Protecting Crops and the Environment, Rothamsted Research, Harpenden, Herts UK
| | - Tom Ashfield
- grid.418374.d0000 0001 2227 9389Department of Protecting Crops and the Environment, Rothamsted Research, Harpenden, Herts UK ,grid.418374.d0000 0001 2227 9389Crop Health and Protection (CHaP), Rothamsted Research, Harpenden, Herts UK
| | - Stefano Torriani
- grid.420222.40000 0001 0669 0426Syngenta Crop Protection AG, Schaffhauserstrasse 101, CH-4332 Stein, Switzerland
| | - Kostya Kanyuka
- grid.418374.d0000 0001 2227 9389Department of Protecting Crops and the Environment, Rothamsted Research, Harpenden, Herts UK ,grid.17595.3f0000 0004 0383 6532Present address: National Institute for Agricultural Botany (NIAB), 93 Lawrence Weaver Road, Cambridge, UK
| | - Kim Hammond-Kosack
- grid.418374.d0000 0001 2227 9389Department of Protecting Crops and the Environment, Rothamsted Research, Harpenden, Herts UK
| | - Stephane Bieri
- grid.420222.40000 0001 0669 0426Syngenta Crop Protection AG, Schaffhauserstrasse 101, CH-4332 Stein, Switzerland
| | - Jason Rudd
- Department of Protecting Crops and the Environment, Rothamsted Research, Harpenden, Herts, UK.
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Blyth HR, Smith D, King R, Bayon C, Ashfield T, Walpole H, Venter E, Ray RV, Kanyuka K, Rudd JJ. Fungal plant pathogen "mutagenomics" reveals tagged and untagged mutations in Zymoseptoria tritici and identifies SSK2 as key morphogenesis and stress-responsive virulence factor. FRONTIERS IN PLANT SCIENCE 2023; 14:1140824. [PMID: 37206970 PMCID: PMC10190600 DOI: 10.3389/fpls.2023.1140824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Accepted: 03/29/2023] [Indexed: 05/21/2023]
Abstract
"Mutagenomics" is the combination of random mutagenesis, phenotypic screening, and whole-genome re-sequencing to uncover all tagged and untagged mutations linked with phenotypic changes in an organism. In this study, we performed a mutagenomics screen on the wheat pathogenic fungus Zymoseptoria tritici for altered morphogenetic switching and stress sensitivity phenotypes using Agrobacterium-mediated "random" T-DNA mutagenesis (ATMT). Biological screening identified four mutants which were strongly reduced in virulence on wheat. Whole genome re-sequencing defined the positions of the T-DNA insertion events and revealed several unlinked mutations potentially affecting gene functions. Remarkably, two independent reduced virulence mutant strains, with similarly altered stress sensitivities and aberrant hyphal growth phenotypes, were found to have a distinct loss of function mutations in the ZtSSK2 MAPKKK gene. One mutant strain had a direct T-DNA insertion affecting the predicted protein's N-terminus, while the other possessed an unlinked frameshift mutation towards the C-terminus. We used genetic complementation to restore both strains' wild-type (WT) function (virulence, morphogenesis, and stress response). We demonstrated that ZtSSK2 has a non-redundant function with ZtSTE11 in virulence through the biochemical activation of the stress-activated HOG1 MAPK pathway. Moreover, we present data suggesting that SSK2 has a unique role in activating this pathway in response to specific stresses. Finally, dual RNAseq-based transcriptome profiling of WT and SSK2 mutant strains revealed many HOG1-dependent transcriptional changes in the fungus during early infection and suggested that the host response does not discriminate between WT and mutant strains during this early phase. Together these data define new genes implicated in the virulence of the pathogen and emphasise the importance of a whole genome sequencing step in mutagenomic discovery pipelines.
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Affiliation(s)
- Hannah R. Blyth
- Protecting Crops and the Environment, Rothamsted Research, Harpenden, United Kingdom
| | - Dan Smith
- Protecting Crops and the Environment, Rothamsted Research, Harpenden, United Kingdom
| | - Robert King
- Protecting Crops and the Environment, Rothamsted Research, Harpenden, United Kingdom
| | - Carlos Bayon
- Protecting Crops and the Environment, Rothamsted Research, Harpenden, United Kingdom
| | - Tom Ashfield
- Crop Health and Protection (CHAP), Rothamsted Research, Harpenden, United Kingdom
| | - Hannah Walpole
- Bioimaging Unit, Rothamsted Research, Harpenden, United Kingdom
| | - Eudri Venter
- Bioimaging Unit, Rothamsted Research, Harpenden, United Kingdom
| | - Rumiana V. Ray
- Division of Plant and Crop Sciences, School of Biosciences, University of Nottingham, Loughborough, United Kingdom
| | - Kostya Kanyuka
- Protecting Crops and the Environment, Rothamsted Research, Harpenden, United Kingdom
| | - Jason J. Rudd
- Protecting Crops and the Environment, Rothamsted Research, Harpenden, United Kingdom
- *Correspondence: Jason J. Rudd,
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Orellana-Torrejon C, Vidal T, Gazeau G, Boixel AL, Gélisse S, Lageyre J, Saint-Jean S, Suffert F. Multiple scenarios for sexual crosses in the fungal pathogen Zymoseptoria tritici on wheat residues: Potential consequences for virulence gene transmission. Fungal Genet Biol 2022; 163:103744. [PMID: 36209959 DOI: 10.1016/j.fgb.2022.103744] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Revised: 08/31/2022] [Accepted: 09/30/2022] [Indexed: 01/06/2023]
Abstract
Little is known about the impact of host immunity on sexual reproduction in fungal pathogens. In particular, it is unclear whether crossing requires both sexual partners to infect living plant tissues. We addressed this issue in a three-year experiment investigating different scenarios of Zymoseptoria tritici crosses according to the virulence ('vir') or avirulence ('avr') of the parents against a qualitative resistance gene. Co-inoculations ('vir × vir', 'avr × vir', 'avr × avr') and single inoculations were performed on a wheat cultivar carrying the Stb16q resistance gene (Cellule) and a susceptible cultivar (Apache), in the greenhouse. We assessed the intensity of asexual reproduction by scoring disease severity, and the intensity of sexual reproduction by counting the ascospores discharged from wheat residues. As expected, disease severity was more intense on Cellule for 'vir × vir' co-inoculations than for 'avr × vir' co-inoculations, with no disease for 'avr × avr'. However, all types of co-inoculation yielded sexual offspring, whether or not the parental strains caused plant symptoms. Parenthood was confirmed by genotyping (SSR markers), and the occurrence of crosses between (co-)inoculated and exogenous strains (other strains from the experiment, or from far away) was determined. We showed that symptomatic asexual infection was not required for a strain to participate in sexual reproduction, and deduced from this result that avirulent strains could be maintained asymptomatically "on" or "in" leaf tissues of plants carrying the corresponding resistant gene for long enough to reproduce sexually. In two of the three years, the intensity of sexual reproduction did not differ between the three types of co-inoculation in Cellule, suggesting that crosses involving avirulent strains are not anecdotal. We discuss the possible mechanisms explaining the maintenance of avirulence in Z. tritici populations and the potential impact of particular resistance deployments such as cultivar mixtures for limiting resistance breakdown.
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Affiliation(s)
- Carolina Orellana-Torrejon
- Université Paris-Saclay, INRAE, UR BIOGER, 91120 Palaiseau, France; Université Paris-Saclay, INRAE, AgroParisTech, UMR ECOSYS, 91120 Palaiseau, France
| | - Tiphaine Vidal
- Université Paris-Saclay, INRAE, UR BIOGER, 91120 Palaiseau, France
| | - Gwilherm Gazeau
- Université Paris-Saclay, INRAE, UR BIOGER, 91120 Palaiseau, France
| | - Anne-Lise Boixel
- Université Paris-Saclay, INRAE, UR BIOGER, 91120 Palaiseau, France
| | - Sandrine Gélisse
- Université Paris-Saclay, INRAE, UR BIOGER, 91120 Palaiseau, France
| | - Jérôme Lageyre
- Université Paris-Saclay, INRAE, AgroParisTech, UMR ECOSYS, 91120 Palaiseau, France
| | - Sébastien Saint-Jean
- Université Paris-Saclay, INRAE, AgroParisTech, UMR ECOSYS, 91120 Palaiseau, France
| | - Frédéric Suffert
- Université Paris-Saclay, INRAE, UR BIOGER, 91120 Palaiseau, France.
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Bock CH, Frusso E, Zoppolo R, Ortiz ER, Shiller J, Charlton ND, Young CA, Randall JJ. Population Genetic Characteristics and Mating Type Frequency of Venturia effusa from Pecan in South America. PHYTOPATHOLOGY 2022; 112:2224-2235. [PMID: 35596236 DOI: 10.1094/phyto-01-22-0031-r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Scab, caused by the plant-pathogenic fungus Venturia effusa, is a major disease of pecan in South America, resulting in loss of quantity and quality of nut yield. Characteristics of the populations of V. effusa in South America are unknown. We used microsatellites to describe the genetic diversity and population structure of V. effusa in South America, and determined the mating type status of the pathogen. The four hierarchically sampled orchard populations from Argentina (AR), Brazil (BRC and BRS), and Uruguay (UR) had moderate to high genotypic and gene diversity. There was evidence of population differentiation (Fst = 0.196) but the correlation between geographic distance and genetic distance was not statistically significant. Genetic differentiation was minimal between the UR, BRC, and BRS populations, and these populations were more clearly differentiated from the AR population. The MAT1-1 and MAT1-2 mating types occurred in all four orchards and their frequencies did not deviate from the 1:1 ratio expected under random mating; however, multilocus linkage equilibrium was rejected in three of the four populations. The population genetics of South American populations of V. effusa has many similarities to the population genetics of V. effusa previously described in the United States. Characterizing the populations genetics and reproductive systems of V. effusa are important to establish the evolutionary potential of the pathogen and, thus, its adaptability-and can provide a basis for informed approaches to utilizing available host resistance and determining phytosanitary needs.
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Affiliation(s)
- Clive H Bock
- United States Department of Agriculture-Agriculture Research Service, Southeastern Fruit and Tree Nut Research Lab, 21 Dunbar Road, Byron, GA 31008, U.S.A
| | - Enrique Frusso
- Instituto de Recursos Biológicos, INTA Castelar, Las Cabañas y De Los Reseros s.n., (1686) Hurlingham, Buenos Aires, Argentina
| | - Roberto Zoppolo
- Instituto Nacional de Investigación Agropecuaria - INIA Las Brujas, Ruta 48 - km 10, El Colorado, Canelones, Uruguay, CP 90200
| | - Edson R Ortiz
- Divinut Indústria de Nozes Ltda., Rodovia BR-153, km 375, CEP 96504-800 - Cachoeira do Sul/RS, Brazil
| | | | - Nikki D Charlton
- Noble Research Institute, 2510 Sam Noble Parkway, Ardmore, OK 73401, U.S.A
| | - Carolyn A Young
- Noble Research Institute, 2510 Sam Noble Parkway, Ardmore, OK 73401, U.S.A
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, 74078, U.S.A
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Bernasconi A, Alassimone J, McDonald BA, Sánchez‐Vallet A. Asexual reproductive potential trumps virulence as a predictor of competitive ability in mixed infections. Environ Microbiol 2022; 24:4369-4381. [PMID: 35437879 PMCID: PMC9790533 DOI: 10.1111/1462-2920.16018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Accepted: 04/13/2022] [Indexed: 12/30/2022]
Abstract
Natural infections frequently involve several co-infecting pathogen strains. These mixed infections can affect the extent of the infection, the transmission success of the pathogen and the eventual epidemic outcome. To date, few studies have investigated how mixed infections affect transmission between hosts. Zymoseptoria tritici is a highly diverse wheat pathogen in which multiple strains often coexist in the same lesion. Here we demonstrate that the most competitive strains often exclude their competitors during serial passages of mixed infections. The outcome of the competition depended on both the host genotype and the genotypes of the competing pathogen strains. Differences in virulence among the strains were not associated with competitive advantages during transmission, while differences in reproductive potential had a strong effect on strain competitive ability. Overall, our findings suggest that host specialization is determined mainly by the ability to successfully transmit offspring to new hosts during mixed infections.
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Affiliation(s)
- Alessio Bernasconi
- Plant Pathology, Institute of Integrative Biology, ETH ZürichZürichCH‐8092Switzerland
| | - Julien Alassimone
- Plant Pathology, Institute of Integrative Biology, ETH ZürichZürichCH‐8092Switzerland
| | - Bruce A. McDonald
- Plant Pathology, Institute of Integrative Biology, ETH ZürichZürichCH‐8092Switzerland
| | - Andrea Sánchez‐Vallet
- Plant Pathology, Institute of Integrative Biology, ETH ZürichZürichCH‐8092Switzerland
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11
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Wang C, Li Y, Wang B, Hu X. Genetic Analysis Reveals Relationships Among Populations of Puccinia striiformis f. sp. tritici from the Longnan, Longdong, and Central Shaanxi Regions of China. PHYTOPATHOLOGY 2022; 112:278-289. [PMID: 34129356 DOI: 10.1094/phyto-07-20-0312-r] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici, is one of the most important diseases of wheat worldwide. In China, Longnan (LN) and Longdong (LD) in the south and east of Gansu province, respectively, are important P. striiformis f. sp. tritici oversummering areas and are a source of P. striiformis f. sp. tritici inoculum for the major wheat-growing regions in eastern China. Central Shaanxi (CS) is a wheat-growing region that acts as an important bridge zone for stripe rust epidemic development between LN and LD in the west and the Huanghuai wheat-growing region in the east, and thus, it plays an essential role in P. striiformis f. sp. tritici epidemics in China. To study the relationships among P. striiformis f. sp. tritici populations in the three regions (LN, LD, and CS), we sampled 284 isolates from different geographic locations. Based on 10 simple sequence repeat markers, the results demonstrated high genetic diversity in all three regions, although diversity did vary among regions, with LN > LD > CS. Genetic differentiation was lower, with more extensive gene flow between LD and CS. P. striiformis f. sp. tritici populations in the CS region were genetically closer to those from LD than those from LN, which may be a result of geographical proximity and topography. A positive and significant correlation existed between linearized fixation index (FST) and the log of geographical distances among all subpopulations. Linkage disequilibrium analysis showed that subpopulations of P. striiformis f. sp. tritici from Qinzhou, Qincheng, Beidao, and Maiji from LN and Qianyang and Longxian from CS were in equilibrium (P > 0.05), suggesting that somatic hybridization and/or sexual reproduction may exist in these subpopulations.
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Affiliation(s)
- Conghao Wang
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Plant Protection, Northwest A&F University, Yangling 712100, China
| | - Yuxiang Li
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Plant Protection, Northwest A&F University, Yangling 712100, China
| | - Baotong Wang
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Plant Protection, Northwest A&F University, Yangling 712100, China
| | - Xiaoping Hu
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Plant Protection, Northwest A&F University, Yangling 712100, China
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12
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Oggenfuss U, Badet T, Wicker T, Hartmann FE, Singh NK, Abraham L, Karisto P, Vonlanthen T, Mundt C, McDonald BA, Croll D. A population-level invasion by transposable elements triggers genome expansion in a fungal pathogen. eLife 2021; 10:e69249. [PMID: 34528512 PMCID: PMC8445621 DOI: 10.7554/elife.69249] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Accepted: 08/28/2021] [Indexed: 12/16/2022] Open
Abstract
Genome evolution is driven by the activity of transposable elements (TEs). The spread of TEs can have deleterious effects including the destabilization of genome integrity and expansions. However, the precise triggers of genome expansions remain poorly understood because genome size evolution is typically investigated only among deeply divergent lineages. Here, we use a large population genomics dataset of 284 individuals from populations across the globe of Zymoseptoria tritici, a major fungal wheat pathogen. We built a robust map of genome-wide TE insertions and deletions to track a total of 2456 polymorphic loci within the species. We show that purifying selection substantially depressed TE frequencies in most populations, but some rare TEs have recently risen in frequency and likely confer benefits. We found that specific TE families have undergone a substantial genome-wide expansion from the pathogen's center of origin to more recently founded populations. The most dramatic increase in TE insertions occurred between a pair of North American populations collected in the same field at an interval of 25 years. We find that both genome-wide counts of TE insertions and genome size have increased with colonization bottlenecks. Hence, the demographic history likely played a major role in shaping genome evolution within the species. We show that both the activation of specific TEs and relaxed purifying selection underpin this incipient expansion of the genome. Our study establishes a model to recapitulate TE-driven genome evolution over deeper evolutionary timescales.
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Affiliation(s)
- Ursula Oggenfuss
- Laboratory of Evolutionary Genetics, Institute of Biology, University of NeuchâtelNeuchatelSwitzerland
| | - Thomas Badet
- Laboratory of Evolutionary Genetics, Institute of Biology, University of NeuchâtelNeuchatelSwitzerland
| | - Thomas Wicker
- Institute for Plant and Microbial Biology, University of ZurichZurichSwitzerland
| | - Fanny E Hartmann
- Ecologie Systématique Evolution, Bâtiment 360, Univ. Paris-Sud, AgroParisTech, CNRS, Université Paris-SaclayOrsayFrance
- Plant Pathology, Institute of Integrative Biology, ETH ZurichZurichSwitzerland
| | - Nikhil Kumar Singh
- Laboratory of Evolutionary Genetics, Institute of Biology, University of NeuchâtelNeuchatelSwitzerland
| | - Leen Abraham
- Laboratory of Evolutionary Genetics, Institute of Biology, University of NeuchâtelNeuchatelSwitzerland
| | - Petteri Karisto
- Plant Pathology, Institute of Integrative Biology, ETH ZurichZurichSwitzerland
| | - Tiziana Vonlanthen
- Plant Pathology, Institute of Integrative Biology, ETH ZurichZurichSwitzerland
| | - Christopher Mundt
- Department of Botany and Plant Pathology, Oregon State UniversityCorvallisUnited States
| | - Bruce A McDonald
- Plant Pathology, Institute of Integrative Biology, ETH ZurichZurichSwitzerland
| | - Daniel Croll
- Laboratory of Evolutionary Genetics, Institute of Biology, University of NeuchâtelNeuchatelSwitzerland
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13
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Kimunye JN, Muzhinji N, Mostert D, Viljoen A, Bester-van der Merwe AE, Mahuku G. Genetic Diversity and Mating Type Distribution of Pseudocercospora fijiensis on Banana in Uganda and Tanzania. PHYTOPATHOLOGY 2021; 111:741-750. [PMID: 32931393 DOI: 10.1094/phyto-04-20-0138-r] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Black Sigatoka, caused by Pseudocercospora fijiensis, is a major foliar disease of banana and plantain worldwide. There are few available data regarding the genetic diversity and population structure of the pathogen in East Africa, which are needed to design effective and durable disease management strategies. We genotyped 319 single-spore isolates of P. fijiensis collected from seven regions in Uganda and Tanzania and five isolates from Nigeria using 16 simple sequence repeat markers and mating type-specific primers. Isolates from each country and region within the country were treated as populations and subpopulations, respectively. A total of 296 multilocus genotypes (MLGs) were recovered, representing a clonal fraction of 7%. Subpopulations had a moderate level of genetic diversity (Hexp = 0.12 to 0.31; mean, 0.29). Mating type distribution did not deviate from equilibrium (MAT1-1: MAT1-2, 1:1 ratio) in Uganda; however, in Tanzania the mating types were not in equilibrium (4:1 ratio). The index of association tests (IA and r̄d) showed that all populations were at linkage equilibrium (P > 0.05), thus supporting the hypothesis of random association of alleles. These findings are consistent with a pathogen that reproduces both clonally and sexually. Low and insignificant levels of population differentiation were detected, with 90% of the variation occurring among isolates within subpopulations. The high intrapopulation variation has implications in breeding for resistance to P. fijiensis because isolates differing in aggressiveness and virulence are likely to exist over small spatial scales. Diverse isolates will be required for resistance screening to ensure selection of banana cultivars with durable resistance to Sigatoka in East Africa.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.
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Affiliation(s)
- Janet N Kimunye
- International Institute of Tropical Agriculture, P.O. Box 7878, Kampala, Uganda
- Department of Plant Pathology, Private Bag X1, Stellenbosch University, Matieland 7602, South Africa
| | - Norman Muzhinji
- Department of Applied and Natural Sciences, Namibia University of Science and Technology, Private Bag 13388, Windhoek, Namibia
| | - Diane Mostert
- Department of Plant Pathology, Private Bag X1, Stellenbosch University, Matieland 7602, South Africa
| | - Altus Viljoen
- Department of Plant Pathology, Private Bag X1, Stellenbosch University, Matieland 7602, South Africa
| | | | - George Mahuku
- International Institute of Tropical Agriculture, P.O. Box 7878, Kampala, Uganda
- International Institute of Tropical Agriculture, P.O. Box, 34441, Dar es Salaam, Tanzania
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Barrett LG, Zala M, Mikaberidze A, Alassimone J, Ahmad M, McDonald BA, Sánchez-Vallet A. Mixed infections alter transmission potential in a fungal plant pathogen. Environ Microbiol 2021; 23:2315-2330. [PMID: 33538383 PMCID: PMC8248022 DOI: 10.1111/1462-2920.15417] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 01/12/2021] [Accepted: 01/28/2021] [Indexed: 01/08/2023]
Abstract
Infections by more than one strain of a pathogen predominate under natural conditions. Mixed infections can have significant, though often unpredictable, consequences for overall virulence, pathogen transmission and evolution. However, effects of mixed infection on disease development in plants often remain unclear and the critical factors that determine the outcome of mixed infections remain unknown. The fungus Zymoseptoria tritici forms genetically diverse infections in wheat fields. Here, for a range of pathogen traits, we experimentally decompose the infection process to determine how the outcomes and consequences of mixed infections are mechanistically realized. Different strains of Z. tritici grow in close proximity and compete in the wheat apoplast, resulting in reductions in growth of individual strains and in pathogen reproduction. We observed different outcomes of competition at different stages of the infection. Overall, more virulent strains had higher competitive ability during host colonization, and less virulent strains had higher transmission potential. We showed that within‐host competition can have a major effect on infection dynamics and pathogen population structure in a pathogen and host genotype‐specific manner. Consequently, mixed infections likely have a major effect on the development of septoria tritici blotch epidemics and the evolution of virulence in Z. tritici.
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Affiliation(s)
- Luke G Barrett
- CSIRO Agriculture and Food, GPO BOX 1700, Canberra, ACT, 2601, Australia
| | - Marcello Zala
- Plant Pathology, Institute of Integrative Biology, ETH Zurich, Universitätstrasse 2, Zurich, 8092, Switzerland
| | - Alexey Mikaberidze
- Plant Pathology, Institute of Integrative Biology, ETH Zurich, Universitätstrasse 2, Zurich, 8092, Switzerland
| | - Julien Alassimone
- Plant Pathology, Institute of Integrative Biology, ETH Zurich, Universitätstrasse 2, Zurich, 8092, Switzerland
| | - Muhammad Ahmad
- Plant Pathology, Institute of Integrative Biology, ETH Zurich, Universitätstrasse 2, Zurich, 8092, Switzerland
| | - Bruce A McDonald
- Plant Pathology, Institute of Integrative Biology, ETH Zurich, Universitätstrasse 2, Zurich, 8092, Switzerland
| | - Andrea Sánchez-Vallet
- Plant Pathology, Institute of Integrative Biology, ETH Zurich, Universitätstrasse 2, Zurich, 8092, Switzerland.,Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM)-Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), Pozuelo de Alarcón, Madrid, Spain
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15
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Francisco CS, Zwyssig MM, Palma-Guerrero J. The role of vegetative cell fusions in the development and asexual reproduction of the wheat fungal pathogen Zymoseptoria tritici. BMC Biol 2020; 18:99. [PMID: 32782023 PMCID: PMC7477884 DOI: 10.1186/s12915-020-00838-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2020] [Accepted: 07/27/2020] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND The ability of fungal cells to undergo cell-to-cell communication and anastomosis, the process of vegetative hyphal fusion, allows them to maximize their overall fitness. Previous studies in a number of fungal species have identified the requirement of several signaling pathways for anastomosis, including the so far best characterized soft (So) gene, and the MAPK pathway components MAK-1 and MAK-2 of Neurospora crassa. Despite the observations of hyphal fusions' involvement in pathogenicity and host adhesion, the connection between cell fusion and fungal lifestyles is still unclear. Here, we address the role of anastomosis in fungal development and asexual reproduction in Zymoseptoria tritici, the most important fungal pathogen of wheat in Europe. RESULTS We show that Z. tritici undergoes self-fusion between distinct cellular structures, and its mechanism is dependent on the initial cell density. Contrary to other fungi, cell fusion in Z. tritici only resulted in cytoplasmic mixing but not in multinucleated cell formation. The deletion of the So orthologous ZtSof1 disrupted cell-to-cell communication affecting both hyphal and germling fusion. We show that Z. tritici mutants for MAPK-encoding ZtSlt2 (orthologous to MAK-1) and ZtFus3 (orthologous to MAK-2) genes also failed to undergo anastomosis, demonstrating the functional conservation of this signaling mechanism across species. Additionally, the ΔZtSof1 mutant was severely impaired in melanization, suggesting that the So gene function is related to melanization. Finally, we demonstrated that anastomosis is dispensable for pathogenicity, but essential for the pycnidium development, and its absence abolishes the asexual reproduction of Z. tritici. CONCLUSIONS We demonstrate the role for ZtSof1, ZtSlt2, and ZtFus3 in cell fusions of Z. tritici. Cell fusions are essential for different aspects of the Z. tritici biology, and the ZtSof1 gene is a potential target to control septoria tritici blotch (STB) disease.
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Affiliation(s)
| | - Maria Manuela Zwyssig
- Plant Pathology Group, Institute of Integrative Biology, ETH Zürich, 8092, Zürich, Switzerland
| | - Javier Palma-Guerrero
- Plant Pathology Group, Institute of Integrative Biology, ETH Zürich, 8092, Zürich, Switzerland.
- New Address: Department of Biointeractions and Crop Protection, Rothamsted Research, Harpenden, UK.
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16
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Mekonnen T, Haileselassie T, Goodwin SB, Tesfayea K. Genetic diversity and population structure of Zymoseptoria tritici in Ethiopia as revealed by microsatellite markers. Fungal Genet Biol 2020; 141:103413. [PMID: 32442667 DOI: 10.1016/j.fgb.2020.103413] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2019] [Revised: 02/02/2020] [Accepted: 05/15/2020] [Indexed: 11/17/2022]
Abstract
Septoria tritici blotch (STB), caused by Zymoseptoria tritici (formerly: Mycosphaerella graminicola or Septoria tritici), is one of the most devastating diseases of wheat globally. Understanding genetic diversity of the pathogen has supreme importance in developing best management strategies. However, there is dearth of information on the genetic structure of Z. tritici populations in Ethiopia. Therefore, the present study was targeted to uncover the genetic diversity and population structure of Z. tritici populations from the major wheat-growing areas of Ethiopia. Totally, 182 Z. tritici isolates representing eight populations were analyzed with 14 microsatellite markers. All the microsatellite loci were polymorphic and highly informative, and hence useful genetic tools to depict the genetic diversity and population structure of the pathogen. A wide range of diversity indices including number of observed alleles, effective number of alleles, Shannon's diversity index, number of private alleles, Nei's gene diversity and percentage of polymorphic loci (PPL) were computed to determine genetic variation within populations. A high within-populations genetic diversity was confirmed with gene diversity index and PPL values ranging from 0.34 - 0.58 and 79-100% with overall mean of 0.45 and 94%, respectively. Analysis of molecular variance (AMOVA) revealed a moderate genetic differentiation where 92% of the total genetic variation resides within populations, leaving only 8% among populations. Cluster (UPGMA), PCoA and STRUCTURE analyses did not group the populations into sharply genetically distinct clusters according to their geographical origins, likely due to high gene flow (Nm = 5.66) and reproductive biology of the pathogen. All individual samples shared alleles from two subgroups (K = 2) evidencing high potential of genetic admixture. In conclusion, the microsatellite markers used in the present study were highly informative and thus, helped to dissect the genetic structures of Z. tritici populations in Ethiopia. Among the studied populations, those of East Shewa, Arsi, South West Shewa and Bale showed a high genetic diversity, and hence these areas can be considered as hot spots for investigations planned on the pathogen and host-pathogen interactions. Therefore, the present study not only enriches missing information in Ethiopia but also provides new insights into the epidemiology and genetic structure of Z. tritici in Africa where the agro-climatic conditions and the wheat cropping systems are different from other parts of the world. Such baseline information is useful for designing and implementing durable and effective management strategies.
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Affiliation(s)
- Tilahun Mekonnen
- Institute of Biotechnology, Addis Ababa University, Addis Ababa, Ethiopia.
| | | | - Stephen B Goodwin
- USDA-Agricultural Research Service, Department of Botany and Plant Pathology, Purdue University, 915 West State Street, West Lafayette, IN 47907-2054, USA.
| | - Kassahun Tesfayea
- Institute of Biotechnology, Addis Ababa University, Addis Ababa, Ethiopia; Ethiopian Biotechnology Institute. Affiliated with Institute of Biotechnology, Addis Ababa University, Addis Ababa, Ethiopia.
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17
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Brito FSD, Santos JRP, Azevedo VCR, Peixouto YS, de Oliveira SA, Ferreira CF, Haddad F, Amorim EP, Fraaije B, Miller RNG. Genetic Diversity and Azole Fungicide Sensitivity in Pseudocercospora musae Field Populations in Brazil. Front Microbiol 2020; 11:99. [PMID: 32117129 PMCID: PMC7011104 DOI: 10.3389/fmicb.2020.00099] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Accepted: 01/17/2020] [Indexed: 11/21/2022] Open
Abstract
Pseudocercospora musae, causal agent of Sigatoka leaf spot, or yellow Sigatoka disease, is considered a major pathogen of banana (Musa spp.). Widely disseminated in Brazil, this study explored the genetic diversity in field populations of the pathogen from production areas in the Distrito Federal and the States of Bahia, Minas Gerais, and Rio Grande do Norte. Resistance to demethylation inhibitor (DMI) fungicides was also examined. For 162 isolates from 10 banana growing regions, analysis of mating type idiomorph frequency was conducted, together with estimation of genetic diversity at 15 microsatellite loci. A total of 149 haplotypes were identified across the examined populations, with an average genetic diversity of 4.06. In general, populations displayed 1:1 proportions of idiomorphs MAT1-1 and MAT1-2, providing evidence for sexual recombination. Multilocus linkage disequilibrium also indicated asexual reproduction contributing to the genetic structure of certain populations. AMOVA revealed that 86.3% of the genetic differentiation of the pathogen occurred among isolates within populations. Discriminant Analysis of Principal Components (DAPC) identified six most probable genetic groups, with no population structure associated with geographic origin or collection site. Although genetic similarity was observed among certain populations from different states, data revealed increasing genetic differentiation with increasing geographic distance, as validated by Mantel’s test (r = 0.19, P < 0.001). On the basis of DMI fungicide sensitivity testing and CYP51 gene sequence polymorphism, isolates from the Distrito Federal separated into two main groups, one with generally higher EC50 values against eight DMI fungicides. A clear phenotype-to-genotype relationship was observed for isolates carrying the CYP51 alteration Y461N. Conventionally adopted fungicides for control of Sigatoka leaf spot are likely to be overcome by combined sexual and asexual reproduction mechanisms in P. musae driving genetic variability. Continued analysis of pathogen genetic diversity and monitoring of DMI sensitivity profiles of Brazilian field populations is essential for the development of integrated control strategies based on host resistance breeding and rational design of fungicide regimes.
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Affiliation(s)
| | - Jansen R P Santos
- Department of Phytopathology, University of Brasília, Brasília, Brazil
| | - Vânia C R Azevedo
- Department of Plant Genetics, Embrapa Recursos Genéticos e Biotecnologia, Brasília, Brazil
| | - Yslai S Peixouto
- Department of Plant Breeding and Phytopathology, Embrapa Mandioca e Fruticultura, Cruz das Almas, Brazil
| | - Saulo A de Oliveira
- Department of Plant Breeding and Phytopathology, Embrapa Mandioca e Fruticultura, Cruz das Almas, Brazil
| | - Cláudia F Ferreira
- Department of Plant Breeding and Phytopathology, Embrapa Mandioca e Fruticultura, Cruz das Almas, Brazil
| | - Fernando Haddad
- Department of Plant Breeding and Phytopathology, Embrapa Mandioca e Fruticultura, Cruz das Almas, Brazil
| | - Edson P Amorim
- Department of Plant Breeding and Phytopathology, Embrapa Mandioca e Fruticultura, Cruz das Almas, Brazil
| | - Bart Fraaije
- Department of Biointeractions and Crop Protection, Rothamsted Research, Harpenden, United Kingdom
| | - Robert N G Miller
- Department of Phytopathology, University of Brasília, Brasília, Brazil
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18
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Anderegg J, Hund A, Karisto P, Mikaberidze A. In-Field Detection and Quantification of Septoria Tritici Blotch in Diverse Wheat Germplasm Using Spectral-Temporal Features. FRONTIERS IN PLANT SCIENCE 2019; 10:1355. [PMID: 31708956 PMCID: PMC6824235 DOI: 10.3389/fpls.2019.01355] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 10/02/2019] [Indexed: 05/26/2023]
Abstract
Hyperspectral remote sensing holds the potential to detect and quantify crop diseases in a rapid and non-invasive manner. Such tools could greatly benefit resistance breeding, but their adoption is hampered by i) a lack of specificity to disease-related effects and ii) insufficient robustness to variation in reflectance caused by genotypic diversity and varying environmental conditions, which are fundamental elements of resistance breeding. We hypothesized that relying exclusively on temporal changes in canopy reflectance during pathogenesis may allow to specifically detect and quantify crop diseases while minimizing the confounding effects of genotype and environment. To test this hypothesis, we collected time-resolved canopy hyperspectral reflectance data for 18 diverse genotypes on infected and disease-free plots and engineered spectral-temporal features representing this hypothesis. Our results confirm the lack of specificity and robustness of disease assessments based on reflectance spectra at individual time points. We show that changes in spectral reflectance over time are indicative of the presence and severity of Septoria tritici blotch (STB) infections. Furthermore, the proposed time-integrated approach facilitated the delineation of disease from physiological senescence, which is pivotal for efficient selection of STB-resistant material under field conditions. A validation of models based on spectral-temporal features on a diverse panel of 330 wheat genotypes offered evidence for the robustness of the proposed method. This study demonstrates the potential of time-resolved canopy reflectance measurements for robust assessments of foliar diseases in the context of resistance breeding.
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Affiliation(s)
- Jonas Anderegg
- Crop Science Group, Institute of Agricultural Sciences, ETH Zurich, Zurich, Switzerland
| | - Andreas Hund
- Crop Science Group, Institute of Agricultural Sciences, ETH Zurich, Zurich, Switzerland
| | - Petteri Karisto
- Plant Pathology Group, Institute of Integrative Biology, ETH Zurich, Zurich, Switzerland
| | - Alexey Mikaberidze
- Plant Pathology Group, Institute of Integrative Biology, ETH Zurich, Zurich, Switzerland
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19
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Koenick LB, Vaghefi N, Knight NL, du Toit LJ, Pethybridge SJ. Genetic Diversity and Differentiation in Phoma betae Populations on Table Beet in New York and Washington States. PLANT DISEASE 2019; 103:1487-1497. [PMID: 31059387 DOI: 10.1094/pdis-09-18-1675-re] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Phoma betae is an important seedborne pathogen of table beet worldwide that is capable of causing foliar, root, and damping-off diseases. Ten microsatellite and mating type markers were developed to investigate the genetics of P. betae populations in table beet root crops in New York and in table beet seed crops in Washington, from where table beet seed is predominantly sourced. The markers were used to characterize 175 isolates comprising five P. betae populations (two from New York and three from Washington), and they were highly polymorphic with an allelic range of 4 to 33 and an average of 11.7 alleles per locus. All populations had high genotypic diversity (Simpson's complement index = 0.857 to 0.924) and moderate allelic diversity (Nei's unbiased gene diversity = 0.582 to 0.653). Greater differentiation observed between populations from the two states compared with populations within the same state suggested that an external inoculum source, such as windblown ascospores, may be homogenizing the populations. However, most genetic diversity (87%) was among individual isolates within populations (pairwise index of population differentiation = 0.127; P = 0.001), suggesting that local within-field inoculum source(s), such as infested field debris or infected weeds, may also be important in initiating disease outbreaks. Standardized index of association, proportion of compatible pairs of loci, and mating type ratio calculations showed evidence for a mixed reproduction mode in all populations. These findings could be useful in designing more effective management strategies for diseases caused by P. betae in table beet production.
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Affiliation(s)
- Lori B Koenick
- 1 Plant Pathology and Plant-Microbe Biology Section, School of Integrative Plant Science, Cornell AgriTech at the New York State Agricultural Experiment Station, Cornell University, Geneva, NY 14456, U.S.A
| | - Niloofar Vaghefi
- 2 Centre for Crop Health, University of Southern Queensland, Toowoomba, Queensland 4350, Australia
| | - Noel L Knight
- 1 Plant Pathology and Plant-Microbe Biology Section, School of Integrative Plant Science, Cornell AgriTech at the New York State Agricultural Experiment Station, Cornell University, Geneva, NY 14456, U.S.A
| | - Lindsey J du Toit
- 3 Washington State University, Mount Vernon Northwestern Washington Research and Extension Center, Mount Vernon, WA 98273, U.S.A
| | - Sarah J Pethybridge
- 1 Plant Pathology and Plant-Microbe Biology Section, School of Integrative Plant Science, Cornell AgriTech at the New York State Agricultural Experiment Station, Cornell University, Geneva, NY 14456, U.S.A
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20
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Suffert F, Delestre G, Gélisse S. Sexual Reproduction in the Fungal Foliar Pathogen Zymoseptoria tritici Is Driven by Antagonistic Density Dependence Mechanisms. MICROBIAL ECOLOGY 2019; 77:110-123. [PMID: 29876608 DOI: 10.1007/s00248-018-1211-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Accepted: 05/22/2018] [Indexed: 05/13/2023]
Abstract
This study provides empirical evidence for antagonistic density dependence mechanisms driving sexual reproduction in the wheat fungal pathogen Zymoseptoria tritici. Biparental crosses with 12 increasing inoculum concentrations, in controlled conditions, showed that sexual reproduction in Z. tritici was impacted by an Allee effect due to mate limitation and a competition with asexual multiplication for resource allocation. The highest number of ascospores discharged was reached at intermediate inoculum concentrations (from 5 × 104 conidia mL-1 to 106 conidia mL-1). Consistent with these results for controlled co-inoculation, we found that the intensity of sexual reproduction varied with both cropping period and the vertical position of the host tissues in the field, with a maximum between 25 and 35 cm above the ground. An optimal lesion density (disease severity of 30 to 45%) maximizing offspring (ascospores) number was established, and its eco-evolutionary consequences are considered here. Two ecological mechanisms may be involved: competition for resources between the two modes of reproduction (decrease in the host resources available for sexual reproduction due to their prior use in asexual multiplication), and competitive disequilibrium between the two parental isolates, due to differential interaction dynamics with the host, for example, leading to an imbalance between mating types. A conceptual model based on these results suggests that sexual reproduction plays a key role in the evolution of pathogenicity traits, including virulence and aggressiveness. Ecological knowledge about the determinants of sexual reproduction in Z. tritici may, therefore, open up new perspectives for the management of other fungal foliar pathogens with dual modes of reproduction.
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Affiliation(s)
- Frédéric Suffert
- UMR BIOGER, INRA, AgroParisTech, Université Paris-Saclay, 78850, Thiverval-Grignon, France.
| | - Ghislain Delestre
- UMR BIOGER, INRA, AgroParisTech, Université Paris-Saclay, 78850, Thiverval-Grignon, France
| | - Sandrine Gélisse
- UMR BIOGER, INRA, AgroParisTech, Université Paris-Saclay, 78850, Thiverval-Grignon, France
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Mating type determination within a microsatellite multiplex for the fungal pathogen Pseudogymnoascus destructans, the causative agent of white-nose disease in bats. CONSERV GENET RESOUR 2018. [DOI: 10.1007/s12686-018-1064-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Siah A, Bomble M, Tisserant B, Cadalen T, Holvoet M, Hilbert JL, Halama P, Reignault P. Genetic Structure of Zymoseptoria tritici in Northern France at Region, Field, Plant, and Leaf Layer Scales. PHYTOPATHOLOGY 2018; 108:1114-1123. [PMID: 29658841 DOI: 10.1094/phyto-09-17-0322-r] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Population genetic structure of the worldwide-distributed wheat pathogen Zymoseptoria tritici has been extensively studied at large geographical scales, but to a much less extent at small or local spatial scales. A total of 627 single-conidial fungal isolates were sampled from several locations in northern France (Hauts-de-France Region) to assess fungal genetic structure at region, field, plant, and leaf layer scales, using highly polymorphic microsatellite markers and mating type idiomorphs. Important and overall similar levels of both gene and genotype diversities (gene diversity values of ≥0.44 and haplotype frequencies of ≥94%) were found at all the examined scales. Such rates of diversity are likely due to an active sexual recombination in the investigated areas, as revealed by equal proportions of the two mating types scored in all sampled populations. Interestingly, a rare occurrence of clones among lesions from a same leaf, as well as among leaves from different plant leaf layers (e.g., upper versus lower leaves), was highlighted, indicating that ascospores contribute much more than expected to Z. tritici epidemics, compared with pycnidiospores. Population structure and analyses of molecular variance revealed significant genetic differentiation at the regional scale (GST = 0.23) and, as expected, not at the other more local scales (GST ≤ 0.01). Further analyses using Bayesian and unweighted neighbor-joining statistical methods detected six genetic clusters within the regional population, overall distributed according to the locations from which the isolates were sampled. Neither clear directional relative migration linked to the geographical distribution of the locations, nor isolation by distance, were observed. Separate evolutionary trajectories caused by selection and adaptations to habitat heterogeneity could be the main forces shaping such structuration. This study provides new insights into the epidemiology and the genetic structure of Z. tritici at small local and, for the first time, at single plant and leaf layer scales. Such findings would be helpful in implementing effective control strategies.
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Affiliation(s)
- Ali Siah
- First, second, fourth, fifth, sixth, and seventh authors: Institut Charles Viollette (ICV-EA 7394), ISA, Université de Lille, SFR Condorcet FR CNRS 3417, 48 bd Vauban, BP 41290, F-59014 Lille Cedex, France; and third and eighth authors: Univ. Littoral Côte d'Opale, Unité de Chimie Environnementale et Interactions sur le Vivant (UCEIV-EA 4492), SFR Condorcet FR CNRS 3417, CS 80699, F-62228, Calais Cedex, France
| | - Myriam Bomble
- First, second, fourth, fifth, sixth, and seventh authors: Institut Charles Viollette (ICV-EA 7394), ISA, Université de Lille, SFR Condorcet FR CNRS 3417, 48 bd Vauban, BP 41290, F-59014 Lille Cedex, France; and third and eighth authors: Univ. Littoral Côte d'Opale, Unité de Chimie Environnementale et Interactions sur le Vivant (UCEIV-EA 4492), SFR Condorcet FR CNRS 3417, CS 80699, F-62228, Calais Cedex, France
| | - Benoit Tisserant
- First, second, fourth, fifth, sixth, and seventh authors: Institut Charles Viollette (ICV-EA 7394), ISA, Université de Lille, SFR Condorcet FR CNRS 3417, 48 bd Vauban, BP 41290, F-59014 Lille Cedex, France; and third and eighth authors: Univ. Littoral Côte d'Opale, Unité de Chimie Environnementale et Interactions sur le Vivant (UCEIV-EA 4492), SFR Condorcet FR CNRS 3417, CS 80699, F-62228, Calais Cedex, France
| | - Thierry Cadalen
- First, second, fourth, fifth, sixth, and seventh authors: Institut Charles Viollette (ICV-EA 7394), ISA, Université de Lille, SFR Condorcet FR CNRS 3417, 48 bd Vauban, BP 41290, F-59014 Lille Cedex, France; and third and eighth authors: Univ. Littoral Côte d'Opale, Unité de Chimie Environnementale et Interactions sur le Vivant (UCEIV-EA 4492), SFR Condorcet FR CNRS 3417, CS 80699, F-62228, Calais Cedex, France
| | - Maxime Holvoet
- First, second, fourth, fifth, sixth, and seventh authors: Institut Charles Viollette (ICV-EA 7394), ISA, Université de Lille, SFR Condorcet FR CNRS 3417, 48 bd Vauban, BP 41290, F-59014 Lille Cedex, France; and third and eighth authors: Univ. Littoral Côte d'Opale, Unité de Chimie Environnementale et Interactions sur le Vivant (UCEIV-EA 4492), SFR Condorcet FR CNRS 3417, CS 80699, F-62228, Calais Cedex, France
| | - Jean-Louis Hilbert
- First, second, fourth, fifth, sixth, and seventh authors: Institut Charles Viollette (ICV-EA 7394), ISA, Université de Lille, SFR Condorcet FR CNRS 3417, 48 bd Vauban, BP 41290, F-59014 Lille Cedex, France; and third and eighth authors: Univ. Littoral Côte d'Opale, Unité de Chimie Environnementale et Interactions sur le Vivant (UCEIV-EA 4492), SFR Condorcet FR CNRS 3417, CS 80699, F-62228, Calais Cedex, France
| | - Patrice Halama
- First, second, fourth, fifth, sixth, and seventh authors: Institut Charles Viollette (ICV-EA 7394), ISA, Université de Lille, SFR Condorcet FR CNRS 3417, 48 bd Vauban, BP 41290, F-59014 Lille Cedex, France; and third and eighth authors: Univ. Littoral Côte d'Opale, Unité de Chimie Environnementale et Interactions sur le Vivant (UCEIV-EA 4492), SFR Condorcet FR CNRS 3417, CS 80699, F-62228, Calais Cedex, France
| | - Philippe Reignault
- First, second, fourth, fifth, sixth, and seventh authors: Institut Charles Viollette (ICV-EA 7394), ISA, Université de Lille, SFR Condorcet FR CNRS 3417, 48 bd Vauban, BP 41290, F-59014 Lille Cedex, France; and third and eighth authors: Univ. Littoral Côte d'Opale, Unité de Chimie Environnementale et Interactions sur le Vivant (UCEIV-EA 4492), SFR Condorcet FR CNRS 3417, CS 80699, F-62228, Calais Cedex, France
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Comparative Methods for Molecular Determination of Host-Specificity Factors in Plant-Pathogenic Fungi. Int J Mol Sci 2018; 19:ijms19030863. [PMID: 29543717 PMCID: PMC5877724 DOI: 10.3390/ijms19030863] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 03/12/2018] [Accepted: 03/14/2018] [Indexed: 12/11/2022] Open
Abstract
Many plant-pathogenic fungi are highly host-specific. In most cases, host-specific interactions evolved at the time of speciation of the respective host plants. However, host jumps have occurred quite frequently, and still today the greatest threat for the emergence of new fungal diseases is the acquisition of infection capability of a new host by an existing plant pathogen. Understanding the mechanisms underlying host-switching events requires knowledge of the factors determining host-specificity. In this review, we highlight molecular methods that use a comparative approach for the identification of host-specificity factors. These cover a wide range of experimental set-ups, such as characterization of the pathosystem, genotyping of host-specific strains, comparative genomics, transcriptomics and proteomics, as well as gene prediction and functional gene validation. The methods are described and evaluated in view of their success in the identification of host-specificity factors and the understanding of their functional mechanisms. In addition, potential methods for the future identification of host-specificity factors are discussed.
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Forward Genetics Approach Reveals Host Genotype-Dependent Importance of Accessory Chromosomes in the Fungal Wheat Pathogen Zymoseptoria tritici. mBio 2017; 8:mBio.01919-17. [PMID: 29184021 PMCID: PMC5705923 DOI: 10.1128/mbio.01919-17] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The fungal wheat pathogen Zymoseptoria tritici possesses a large complement of accessory chromosomes showing presence/absence polymorphism among isolates. These chromosomes encode hundreds of genes; however, their functional role and why the chromosomes have been maintained over long evolutionary times are so far not known. In this study, we addressed the functional relevance of eight accessory chromosomes in reference isolate IPO323. We induced chromosome losses by inhibiting the β-tubulin assembly during mitosis using carbendazim and generated several independent isogenic strains, each lacking one of the accessory chromosomes. We confirmed chromosome losses by electrophoretic karyotyping and whole-genome sequencing. To assess the importance of the individual chromosomes during host infection, we performed in planta assays comparing disease development results in wild-type and chromosome mutant strains. Loss of the accessory chromosomes 14, 16, 18, 19, and 21 resulted in increased virulence on wheat cultivar Runal but not on cultivars Obelisk, Titlis, and Riband. Moreover, some accessory chromosomes affected the switch from biotrophy to necrotrophy as strains lacking accessory chromosomes 14, 18, 19, and 21 showed a significantly earlier onset of necrosis than the wild type on the Runal cultivar. In general, we observed that the timing of the lifestyle switch affects the fitness of Z. tritici. Taking the results together, this study was the first to use a forward-genetics approach to demonstrate a cultivar-dependent functional relevance of the accessory chromosomes of Z. tritici during host infection. Zymoseptoria tritici is a prominent fungal pathogen of wheat of worldwide distribution. This fungus shows a remarkable genome organization, with a large number of chromosomes that are present in only some isolates and therefore considered to be “accessory” chromosomes. To date, the function of these accessory chromosomes in Z. tritici has been unknown, although their maintenance in the species over evolutionary times suggests a functional relevance. Here we deleted whole accessory chromosomes to test the effect of these chromosomes on host specificity and virulence of the fungus. We show for the first time that some accessory chromosomes of Z. tritici affect the fitness of the fungus during host infection in a cultivar-dependent manner. These results show that the accessory chromosomes encode host-specific virulence determinants having a negative effect on fitness. Understanding the population dynamic of the accessory chromosomes and the molecular interaction of pathogen and plant traits is crucial to improve wheat-breeding strategies.
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Puri KD, Gurung S, Short DPG, Atallah ZK, Sandoya G, Davis RM, Hayes RJ, Subbarao KV. Short-Term Host Selection Pressure Has Little Effect on the Evolution of a Monoclonal Population of Verticillium dahliae Race 1. PHYTOPATHOLOGY 2017; 107:1417-1425. [PMID: 28653580 DOI: 10.1094/phyto-02-17-0071-r] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Understanding pathogen evolution over time is vital for plant breeding and deployment of host resistance. In the context of a soilborne pathogen, the potential of host-directed evolution of a Verticillium dahliae race 1 isolate and genotypic variation of V. dahliae associated with two major hosts (lettuce and tomato) were determined. In total, 427 isolates were recovered over 6 years from a resistance screening nursery infested with a single V. dahliae race 1 isolate. In a separate study, an additional 206 isolates representing 163 and 43 isolates from commercial lettuce and tomato fields, respectively, were collected. Analyses of isolates recovered from the screening nursery over 6 years revealed no changes in the race and mating type composition but did uncover seven simple sequence repeat (SSR) variant genotypes. No significant genotypic variation in V. dahliae was observed between or within fields of either lettuce or tomato but pathogen populations were significantly differentiated between these two hosts. Replicated virulence assays of variant SSR genotypes on lettuce differential cultivars suggested no significant difference in virulence from the wild-type race 1 isolate introduced into the field. This suggests that deployed race 1 host resistance will be robust against the widespread race 1 populations in lettuce-growing regions at least for 6 years unless novel pathogen genotypes or races are introduced into the system.
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Affiliation(s)
- Krishna D Puri
- First, third, sixth, and eighth authors: Department of Plant Pathology, University of California, Davis; second author: Sakata Seed America, Salinas, CA; fourth author: Hartnell College, Salinas, CA 93905; fifth author: Department of Horticultural Science, Everglades Research and Education Center, University of Florida, Belle Glade; and seventh author: United States Department of Agriculture-Agricultural Research Service, Salinas, CA
| | - Suraj Gurung
- First, third, sixth, and eighth authors: Department of Plant Pathology, University of California, Davis; second author: Sakata Seed America, Salinas, CA; fourth author: Hartnell College, Salinas, CA 93905; fifth author: Department of Horticultural Science, Everglades Research and Education Center, University of Florida, Belle Glade; and seventh author: United States Department of Agriculture-Agricultural Research Service, Salinas, CA
| | - Dylan P G Short
- First, third, sixth, and eighth authors: Department of Plant Pathology, University of California, Davis; second author: Sakata Seed America, Salinas, CA; fourth author: Hartnell College, Salinas, CA 93905; fifth author: Department of Horticultural Science, Everglades Research and Education Center, University of Florida, Belle Glade; and seventh author: United States Department of Agriculture-Agricultural Research Service, Salinas, CA
| | - Z K Atallah
- First, third, sixth, and eighth authors: Department of Plant Pathology, University of California, Davis; second author: Sakata Seed America, Salinas, CA; fourth author: Hartnell College, Salinas, CA 93905; fifth author: Department of Horticultural Science, Everglades Research and Education Center, University of Florida, Belle Glade; and seventh author: United States Department of Agriculture-Agricultural Research Service, Salinas, CA
| | - German Sandoya
- First, third, sixth, and eighth authors: Department of Plant Pathology, University of California, Davis; second author: Sakata Seed America, Salinas, CA; fourth author: Hartnell College, Salinas, CA 93905; fifth author: Department of Horticultural Science, Everglades Research and Education Center, University of Florida, Belle Glade; and seventh author: United States Department of Agriculture-Agricultural Research Service, Salinas, CA
| | - R Michael Davis
- First, third, sixth, and eighth authors: Department of Plant Pathology, University of California, Davis; second author: Sakata Seed America, Salinas, CA; fourth author: Hartnell College, Salinas, CA 93905; fifth author: Department of Horticultural Science, Everglades Research and Education Center, University of Florida, Belle Glade; and seventh author: United States Department of Agriculture-Agricultural Research Service, Salinas, CA
| | - Ryan J Hayes
- First, third, sixth, and eighth authors: Department of Plant Pathology, University of California, Davis; second author: Sakata Seed America, Salinas, CA; fourth author: Hartnell College, Salinas, CA 93905; fifth author: Department of Horticultural Science, Everglades Research and Education Center, University of Florida, Belle Glade; and seventh author: United States Department of Agriculture-Agricultural Research Service, Salinas, CA
| | - Krishna V Subbarao
- First, third, sixth, and eighth authors: Department of Plant Pathology, University of California, Davis; second author: Sakata Seed America, Salinas, CA; fourth author: Hartnell College, Salinas, CA 93905; fifth author: Department of Horticultural Science, Everglades Research and Education Center, University of Florida, Belle Glade; and seventh author: United States Department of Agriculture-Agricultural Research Service, Salinas, CA
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Mixed-reproductive strategies, competitive mating-type distribution and life cycle of fourteen black morel species. Sci Rep 2017; 7:1493. [PMID: 28473711 PMCID: PMC5431422 DOI: 10.1038/s41598-017-01682-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 03/31/2017] [Indexed: 02/01/2023] Open
Abstract
Morchella species are well known world-round as popular and prized edible fungi due to their unique culinary flavor. Recently, several species have been successfully cultivated in China. However, their reproductive modes are still unknown, and their basic biology needs to be elucidated. Here, we use the morel genome information to investigate mating systems and life cycles of fourteen black morel species. Mating type-specific primers were developed to screen and genotype ascospores, hymenia and stipes from 223 ascocarps of the 14 species from Asia and Europe. Our data indicated that they are all heterothallic and their life cycles are predominantly haploid, but sterile haploid fruiting also exists. Ascospores in all species are mostly haploid, homokaryotic, and multinuclear, whereas aborted ascospores without any nuclei were also detected. Interestingly, we monitored divergent spatial distribution of both mating types in natural morel populations and cultivated sites, where the fertile tissue of fruiting bodies usually harbored both mating types, whereas sterile tissue of wild morels constantly had one MAT allele, while the sterile tissue of cultivated strains always exhibited both MAT alleles. Furthermore, MAT1-1-1 was detected significantly more commonly than MAT1-2-1 in natural populations, which strongly suggested a competitive advantage for MAT1-1 strains.
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Meamiche Neddaf H, Aouini L, Bouznad Z, Kema GHJ. Equal Distribution of Mating Type Alleles and the Presence of Strobilurin Resistance in Algerian Zymoseptoria tritici Field Populations. PLANT DISEASE 2017; 101:544-549. [PMID: 30677359 DOI: 10.1094/pdis-03-16-0298-re] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Zymoseptoria tritici, the causal agent of septoria tritici blotch, is an important wheat pathogen responsible for high yield losses worldwide. The assessment of the distribution of both mating type idiomorphs was studied in several wheat-growing areas in North Algeria. Both mating types occurred at all spatial scales tested and showed an equal frequency distribution at the country level, with 53% for Mat1-1 and 47% for Mat1-2. At finer scales, co-occurrence of both mating types was found in 38% of leaves analyzed and 44% of the studied lesions. Additionally, efficacy reduction of strobilurin applications prompted us to study strobilurin resistance conferred by the G143A substitution in the mitochondrial cytochrome b gene, which was found for the first time in six strains. The results suggest that the Algerian Z. tritici population undergoes frequent sexual reproduction mirrored by co-occurrence of both mating types, which likely will rapidly increase the fraction of strobilurin-resistant isolates in the Algerian population, as has been shown in all other regions where strobilurin resistance surfaced.
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Affiliation(s)
- Hayet Meamiche Neddaf
- Ecole Nationale Supérieure d'Agronomie, Laboratoire de Phytopathologie et de Biologie Moléculaire, El Harrach, Algérie; and Institut National de Recherche Agronomique d'Algérie, Division de Biotechnologies et d'Amélioration des Plantes, El Harrach, Algérie
| | - Lamia Aouini
- Wageningen University and Research Center, Wageningen, The Netherlands
| | - Zouaoui Bouznad
- Ecole Nationale Supérieure d'Agronomie, Laboratoire de Phytopathologie et de Biologie Moléculaire
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Hu X, Ma L, Liu T, Wang C, Peng Y, Pu Q, Xu X. Population Genetic Analysis of Puccinia striiformis f. sp. tritici Suggests Two Distinct Populations in Tibet and the Other Regions of China. PLANT DISEASE 2017; 101:288-296. [PMID: 30681929 DOI: 10.1094/pdis-02-16-0190-re] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is an important disease on wheat, seriously threatening wheat production worldwide. China is one of the largest stripe rust epidemic regions in the world. The pathogen sexual reproduction and migration routes between Tibet and the other regions in China are still unknown. In this study, we obtained 961 Pst isolates from 1,391 wheat leaf samples from Gansu (277), Shaanxi (253), Sichuan (172), and Tibet (259), comprising 13 natural populations, and genotyped them with simple sequence repeat (SSR) markers. The isolates can be divided into two distinct clusters based on DAPC and STRUCTURE analyses. The genetic diversity of Longnan (in Gansu) and Yibin (in Sichuan) populations was the highest and lowest among the 13 populations, respectively. The hypothesis of multilocus linkage disequilibrium was rejected for the populations from Linzhi in the Himalayan, Longnan, Hanzhong, Guangyuan, Mianyang, Liangshan, and Chendu in the south Qinling Mountains at the level of P = 0.01, which indicated significant linkage among markers in these populations. Populations in the other regions had extensive gene exchange (Nm > 4); little gene exchange was found between Tibet and the other regions (Nm < 1). The results suggest that the Tibet epidemic region of Pst is highly differentiated from the other epidemic regions in China.
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Affiliation(s)
- Xiaoping Hu
- State Key Laboratory of Crop Stress Biology for Arid Areas, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Lijie Ma
- State Key Laboratory of Crop Stress Biology for Arid Areas, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Taiguo Liu
- State Key Laboratory for the Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Science, Beijing 100193, China
| | - Conghao Wang
- College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Yuelin Peng
- Tibet Agricultural and Animal Husbandry College, Linzhi 860000, China
| | - Qiong Pu
- Tibet Autonomous Region Agricultural Technology Extension and Service Center, Lhasa 850000, Tibet
| | - Xiangming Xu
- NIAB East Malling Research, New Road, East Malling, ME19 6BJ, Kent, U.K
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Pearce TL, Scott JB, Hay FS, Pethybridge SJ. Mating-Type Gene Structure and Spatial Distribution of Didymella tanaceti in Pyrethrum Fields. PHYTOPATHOLOGY 2016; 106:1521-1529. [PMID: 27398744 DOI: 10.1094/phyto-01-16-0038-r] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Tan spot of pyrethrum (Tanacetum cinerariifolium) is caused by the ascomycete Didymella tanaceti. To assess the evolutionary role of ascospores in the assumed asexual species, the structure and arrangement of mating-type (MAT) genes were examined. A single MAT1-1 or MAT1-2 idiomorph was identified in all isolates examined, indicating that the species is heterothallic. The idiomorphs were flanked upstream and downstream by regions encoding pyridoxamine phosphate oxidase-like and DNA lyase-like proteins, respectively. A multiplex MAT-specific polymerase chain reaction assay was developed and used to genotype 325 isolates collected within two transects in each of four fields in Tasmania, Australia. The ratio of isolates of each mating-type in each transect was consistent with a 1:1 ratio. The spatial distribution of the isolates of the two mating-types within each transect was random for all except one transect for MAT1-1 isolates, indicating that clonal patterns of each mating-type were absent. However, evidence of a reduced selection pressure on MAT1-1 isolates was observed, with a second haplotype of the MAT1-1-1 gene identified in 4.4% of MAT1-1 isolates. In vitro crosses between isolates with opposite mating-types failed to produce ascospores. Although the sexual morph could not be induced, the occurrence of both mating-types in equal frequencies suggested that a cryptic sexual mode of reproduction may occur within field populations.
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Affiliation(s)
- Tamieka L Pearce
- First and second authors: Tasmanian Institute of Agriculture, School of Land and Food, University of Tasmania, Burnie, Tasmania 7320, Australia; and third and fourth authors: Cornell University, School of Integrative Plant Science, Section of Plant Pathology and Plant-Microbe Biology, Cornell University, Geneva, NY 14456
| | - Jason B Scott
- First and second authors: Tasmanian Institute of Agriculture, School of Land and Food, University of Tasmania, Burnie, Tasmania 7320, Australia; and third and fourth authors: Cornell University, School of Integrative Plant Science, Section of Plant Pathology and Plant-Microbe Biology, Cornell University, Geneva, NY 14456
| | - Frank S Hay
- First and second authors: Tasmanian Institute of Agriculture, School of Land and Food, University of Tasmania, Burnie, Tasmania 7320, Australia; and third and fourth authors: Cornell University, School of Integrative Plant Science, Section of Plant Pathology and Plant-Microbe Biology, Cornell University, Geneva, NY 14456
| | - Sarah J Pethybridge
- First and second authors: Tasmanian Institute of Agriculture, School of Land and Food, University of Tasmania, Burnie, Tasmania 7320, Australia; and third and fourth authors: Cornell University, School of Integrative Plant Science, Section of Plant Pathology and Plant-Microbe Biology, Cornell University, Geneva, NY 14456
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Mating type genes in the genus Neofusicoccum: Mating strategies and usefulness in species delimitation. Fungal Biol 2016; 121:394-404. [PMID: 28317541 DOI: 10.1016/j.funbio.2016.08.011] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Accepted: 08/25/2016] [Indexed: 12/16/2022]
Abstract
The genus Neofusicoccum includes species with wide geographical and plant host distribution, some of them of economic importance. The genus currently comprises 27 species that are difficult to identify based on morphological features alone. Thus, species differentiation is based on phylogenetic species recognition using multigene genealogies. In this study, we characterised the mating type genes of Neofusicoccum species. Specific primers were designed to amplify and sequence MAT genes in several species and a PCR-based mating type diagnostic assay was developed. Homothallism was the predominant mating strategy among the species tested. Furthermore, the potential of mating type gene sequences for species delimitation was evaluated. Phylogenetic analyses were performed on both MAT genes and compared with multigene genealogies using sequences of the ribosomal internal transcribed spacer region, translation elongation factor 1-alpha and beta-tubulin. Phylogenies based on mating type genes could discriminate between the species analysed and are in concordance with the results obtained with the more conventional multilocus phylogenetic analysis approach. Thus, MAT genes represent a powerful tool to delimit cryptic species in the genus Neofusicoccum.
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McDonald BA, Mundt CC. How Knowledge of Pathogen Population Biology Informs Management of Septoria Tritici Blotch. PHYTOPATHOLOGY 2016; 106:948-55. [PMID: 27111799 DOI: 10.1094/phyto-03-16-0131-rvw] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Zymoseptoria tritici (previously Mycosphaerella graminicola) causes Septoria tritici blotch (STB) on wheat. The population biology of Z. tritici has been exceptionally well characterized as a result of intensive studies conducted over nearly 30 years. These studies provided important insights into the biology, epidemiology and evolutionary history of Z. tritici that will prove useful for management of STB. The well-documented, rapid adaptation of Z. tritici populations to fungicide applications and deployment of wheat cultivars carrying both major gene and quantitative resistance reflects the high evolutionary potential predicted by the large effective population size, high degree of gene flow and high levels of recombination found in field populations of Z. tritici globally. QST studies that assessed the global diversity for several important quantitative traits confirmed the adaptive potential of field populations and laid the groundwork for quantitative trait loci (QTL) mapping studies. QTL mapping elucidated the genetic architecture of each trait and led to identification of candidate genes affecting fungicide resistance, thermal adaptation, virulence, and host specialization. The insights that emerged through these analyses of Z. tritici population biology can now be used to generate actionable disease management strategies aimed at sustainably reducing losses due to STB. The high evolutionary potential found in field populations of Z. tritici requires deployment of a corresponding dynamically diverse set of control measures that integrate cultural, chemical, biological and resistance breeding strategies. In this review, we describe and prioritize STB control strategies based on current knowledge of Z. tritici population biology and propose a future research agenda oriented toward long-term STB management.
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Affiliation(s)
- Bruce A McDonald
- First author: Plant Pathology, Institute of Integrative Biology, ETH Zurich, CH-8092 Zurich, Switzerland; and second author: Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331
| | - Christopher C Mundt
- First author: Plant Pathology, Institute of Integrative Biology, ETH Zurich, CH-8092 Zurich, Switzerland; and second author: Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331
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Palma-Guerrero J, Torriani SFF, Zala M, Carter D, Courbot M, Rudd JJ, McDonald BA, Croll D. Comparative transcriptomic analyses of Zymoseptoria tritici strains show complex lifestyle transitions and intraspecific variability in transcription profiles. MOLECULAR PLANT PATHOLOGY 2016; 17:845-59. [PMID: 26610174 PMCID: PMC6638511 DOI: 10.1111/mpp.12333] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 10/08/2015] [Accepted: 10/09/2015] [Indexed: 05/03/2023]
Abstract
Zymoseptoria tritici causes Septoria tritici blotch (STB) on wheat. The disease interaction is characterized by clearly defined temporal phases of infection, ultimately resulting in the death of host tissue. Zymoseptoria tritici is a highly polymorphic species with significant intraspecific variation in virulence profiles. We generated a deep transcriptomic sequencing dataset spanning the entire time course of an infection using a previously uncharacterized, highly virulent Z. tritici strain isolated from a Swiss wheat field. We found that seven clusters of gene transcription profiles explained the progression of the infection. The earliest highly up-regulated genes included chloroperoxidases, which may help the fungus cope with plant defences. The onset of necrotrophy was characterized by a concerted up-regulation of proteases, plant cell wall-degrading enzymes and lipases. Functions related to nutrition and growth characterized late necrotrophy and the transition to saprotrophic growth on dead plant tissue. We found that the peak up-regulation of genes essential for mating coincided with the necrotrophic phase. We performed an intraspecies comparative transcriptomics analysis using a comparable time course infection experiment of the genome reference isolate IPO323. Major components of the fungal infection transcriptome were conserved between the two strains. However, individual small, secreted proteins, proteases and cell wall-degrading enzymes showed strongly differentiated transcriptional profiles between isolates. Our analyses illustrate that successful STB infections involve complex transcriptomic remodelling to up-regulate distinct gene functions. Heterogeneity in transcriptomes among isolates may explain some of the considerable variation in virulence and host specialization found within the species.
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Affiliation(s)
- Javier Palma-Guerrero
- Plant Pathology, Institute of Integrative Biology, ETH Zurich, 8092, Zurich, Switzerland
| | - Stefano F F Torriani
- Plant Pathology, Institute of Integrative Biology, ETH Zurich, 8092, Zurich, Switzerland
- Syngenta Crop Protection AG, Schaffhauserstrasse, 4332, Stein, Switzerland
| | - Marcello Zala
- Plant Pathology, Institute of Integrative Biology, ETH Zurich, 8092, Zurich, Switzerland
| | - Dee Carter
- School of Molecular Bioscience, University of Sydney, Sydney, NSW, Australia
| | - Mikaël Courbot
- Syngenta Crop Protection AG, Schaffhauserstrasse, 4332, Stein, Switzerland
| | - Jason J Rudd
- Department of Plant Biology and Crop Science, Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, UK
| | - Bruce A McDonald
- Plant Pathology, Institute of Integrative Biology, ETH Zurich, 8092, Zurich, Switzerland
| | - Daniel Croll
- Plant Pathology, Institute of Integrative Biology, ETH Zurich, 8092, Zurich, Switzerland
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Population genetic analysis reveals cryptic sex in the phytopathogenic fungus Alternaria alternata. Sci Rep 2015; 5:18250. [PMID: 26666175 PMCID: PMC4678894 DOI: 10.1038/srep18250] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Accepted: 11/16/2015] [Indexed: 11/08/2022] Open
Abstract
Reproductive mode can impact population genetic dynamics and evolutionary landscape of plant pathogens as well as on disease epidemiology and management. In this study, we monitored the spatial dynamics and mating type idiomorphs in ~700 Alternaria alternata isolates sampled from the main potato production areas in China to infer the mating system of potato early blight. Consistent with the expectation of asexual species, identical genotypes were recovered from different locations separated by hundreds of kilometers of geographic distance and spanned across many years. However, high genotype diversity, equal MAT1-1 and MAT1-2 frequencies within and among populations, no genetic differentiation and phylogenetic association between two mating types, combined with random association amongst neutral markers in some field populations, suggested that sexual reproduction may also play an important role in the epidemics and evolution of the pathogen in at least half of the populations assayed despite the fact that no teleomorphs have been observed yet naturally or artificially. Our results indicated that A. alternata may adopt an epidemic mode of reproduction by combining many cycles of asexual propagation with fewer cycles of sexual reproduction, facilitating its adaptation to changing environments and making the disease management on potato fields even more difficult.
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The Impact of Recombination Hotspots on Genome Evolution of a Fungal Plant Pathogen. Genetics 2015; 201:1213-28. [PMID: 26392286 DOI: 10.1534/genetics.115.180968] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 09/17/2015] [Indexed: 12/30/2022] Open
Abstract
Recombination has an impact on genome evolution by maintaining chromosomal integrity, affecting the efficacy of selection, and increasing genetic variability in populations. Recombination rates are a key determinant of the coevolutionary dynamics between hosts and their pathogens. Historic recombination events created devastating new pathogens, but the impact of ongoing recombination in sexual pathogens is poorly understood. Many fungal pathogens of plants undergo regular sexual cycles, and sex is considered to be a major factor contributing to virulence. We generated a recombination map at kilobase-scale resolution for the haploid plant pathogenic fungus Zymoseptoria tritici. To account for intraspecific variation in recombination rates, we constructed genetic maps from two independent crosses. We localized a total of 10,287 crossover events in 441 progeny and found that recombination rates were highly heterogeneous within and among chromosomes. Recombination rates on large chromosomes were inversely correlated with chromosome length. Short accessory chromosomes often lacked evidence for crossovers between parental chromosomes. Recombination was concentrated in narrow hotspots that were preferentially located close to telomeres. Hotspots were only partially conserved between the two crosses, suggesting that hotspots are short-lived and may vary according to genomic background. Genes located in hotspot regions were enriched in genes encoding secreted proteins. Population resequencing showed that chromosomal regions with high recombination rates were strongly correlated with regions of low linkage disequilibrium. Hence, genes in pathogen recombination hotspots are likely to evolve faster in natural populations and may represent a greater threat to the host.
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Suffert F, Ravigné V, Sache I. Seasonal Changes Drive Short-Term Selection for Fitness Traits in the Wheat Pathogen Zymoseptoria tritici. Appl Environ Microbiol 2015; 81:6367-79. [PMID: 26150467 PMCID: PMC4542257 DOI: 10.1128/aem.00529-15] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2015] [Accepted: 07/01/2015] [Indexed: 01/30/2023] Open
Abstract
In a cross-infection experiment, we investigated how seasonal changes can affect adaptation patterns in a Zymoseptoria tritici population. The fitness of isolates sampled on wheat leaves at the beginning and at the end of a field epidemic was assessed under environmental conditions (temperature and host stage) to which the local pathogen population was successively exposed. Isolates of the final population were more aggressive, and showed greater sporulation intensity under winter conditions and a shorter latency period (earlier sporulation) under spring conditions, than isolates of the initial population. These differences, complemented by lower between-genotype variability in the final population, exhibited an adaptation pattern with three striking features: (i) the pathogen responded synchronously to temperature and host stage conditions; (ii) the adaptation concerned two key fitness traits; (iii) adaptation to one trait (greater sporulation intensity) was expressed under winter conditions while, subsequently, adaptation to the other trait (shorter latency period) was expressed under spring conditions. This can be interpreted as the result of short-term selection, driven by abiotic and biotic factors. This case study cannot yet be generalized but suggests that seasonality may play an important role in shaping the variability of fitness traits. These results further raise the question of possible counterselection during the interepidemic period. While we did not find any trade-off between clonal multiplication on leaves during the epidemic period and clonal spore production on debris, we suggest that final populations could be counterselected by an Allee effect, mitigating the potential impact of seasonal selection on long-term dynamics.
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Affiliation(s)
- Frédéric Suffert
- INRA, UMR1290 BIOGER, Campus AgroParisTech, Thiverval-Grignon, France
| | | | - Ivan Sache
- AgroParisTech, UMR1290 BIOGER, Campus AgroParisTech, Thiverval-Grignon, France
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Singh G, Dal Grande F, Werth S, Scheidegger C. Long-term consequences of disturbances on reproductive strategies of the rare epiphytic lichen Lobaria pulmonaria: clonality a gift and a curse. FEMS Microbiol Ecol 2014; 91:1-11. [DOI: 10.1093/femsec/fiu009] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
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Quantitative trait locus mapping of melanization in the plant pathogenic fungus Zymoseptoria tritici. G3-GENES GENOMES GENETICS 2014; 4:2519-33. [PMID: 25360032 PMCID: PMC4267946 DOI: 10.1534/g3.114.015289] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Melanin plays an important role in virulence and antimicrobial resistance in several fungal pathogens. The wheat pathogen Zymoseptoria tritici is important worldwide, but little is known about the genetic architecture of pathogenicity, including the production of melanin. Because melanin production can exhibit complex inheritance, we used quantitative trait locus (QTL) mapping in two crosses to identify the underlying genes. Restriction site−associated DNA sequencing was used to genotype 263 (cross 1) and 261 (cross 2) progeny at ~8500 single-nucleotide polymorphisms and construct two dense linkage maps. We measured gray values, representing degrees of melanization, for single-spore colonies growing on Petri dishes by using a novel image-processing approach that enabled high-throughput phenotyping. Because melanin production can be affected by stress, each offspring was grown in two stressful environments and one control environment. We detected six significant QTL in cross 1 and nine in cross 2, with three QTL shared between the crosses. Different QTL were identified in different environments and at different colony ages. By obtaining complete genome sequences for the four parents and analyzing sequence variation in the QTL confidence intervals, we identified 16 candidate genes likely to affect melanization. One of these candidates was PKS1, a polyketide synthase gene known to play a role in the synthesis of dihydroxynaphthalene melanin. Three candidate quantitative trait nucleotides were identified in PKS1. Many of the other candidate genes were not previously associated with melanization.
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Perez-Nadales E, Nogueira MFA, Baldin C, Castanheira S, El Ghalid M, Grund E, Lengeler K, Marchegiani E, Mehrotra PV, Moretti M, Naik V, Oses-Ruiz M, Oskarsson T, Schäfer K, Wasserstrom L, Brakhage AA, Gow NAR, Kahmann R, Lebrun MH, Perez-Martin J, Di Pietro A, Talbot NJ, Toquin V, Walther A, Wendland J. Fungal model systems and the elucidation of pathogenicity determinants. Fungal Genet Biol 2014; 70:42-67. [PMID: 25011008 PMCID: PMC4161391 DOI: 10.1016/j.fgb.2014.06.011] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Revised: 06/23/2014] [Accepted: 06/25/2014] [Indexed: 12/05/2022]
Abstract
Fungi have the capacity to cause devastating diseases of both plants and animals, causing significant harvest losses that threaten food security and human mycoses with high mortality rates. As a consequence, there is a critical need to promote development of new antifungal drugs, which requires a comprehensive molecular knowledge of fungal pathogenesis. In this review, we critically evaluate current knowledge of seven fungal organisms used as major research models for fungal pathogenesis. These include pathogens of both animals and plants; Ashbya gossypii, Aspergillus fumigatus, Candida albicans, Fusarium oxysporum, Magnaporthe oryzae, Ustilago maydis and Zymoseptoria tritici. We present key insights into the virulence mechanisms deployed by each species and a comparative overview of key insights obtained from genomic analysis. We then consider current trends and future challenges associated with the study of fungal pathogenicity.
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Affiliation(s)
- Elena Perez-Nadales
- Department of Genetics, Edificio Gregor Mendel, Planta 1. Campus de Rabanales, University of Cordoba, 14071 Cordoba, Spain.
| | | | - Clara Baldin
- Department of Molecular and Applied Microbiology, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute (HKI), Beutembergstr. 11a, 07745 Jena, Germany; Department of Microbiology and Molecular Biology, Institute of Microbiology, Friedrich Schiller University Jena, Beutenbergstr. 11a, 07745 Jena, Germany
| | - Sónia Castanheira
- Instituto de Biología Funcional y GenómicaCSIC, Universidad de Salamanca, 37007 Salamanca, Spain
| | - Mennat El Ghalid
- Department of Genetics, Edificio Gregor Mendel, Planta 1. Campus de Rabanales, University of Cordoba, 14071 Cordoba, Spain
| | - Elisabeth Grund
- Functional Genomics of Plant Pathogenic Fungi, UMR 5240 CNRS-UCB-INSA-Bayer SAS, Bayer CropScience, 69263 Lyon, France
| | - Klaus Lengeler
- Carlsberg Laboratory, Department of Yeast Genetics, Gamle Carlsberg Vej 10, DK-1799, Copenhagen V, Denmark
| | - Elisabetta Marchegiani
- Evolution and Genomics of Plant Pathogen Interactions, UR 1290 INRA, BIOGER-CPP, Campus AgroParisTech, 78850 Thiverval-Grignon, France
| | - Pankaj Vinod Mehrotra
- Aberdeen Fungal Group, School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | - Marino Moretti
- Max-Planck-Institute for Terrestrial Microbiology, Department of Organismic Interactions, Karl-von-Frisch-Strasse 10, D-35043 Marburg, Germany
| | - Vikram Naik
- Max-Planck-Institute for Terrestrial Microbiology, Department of Organismic Interactions, Karl-von-Frisch-Strasse 10, D-35043 Marburg, Germany
| | - Miriam Oses-Ruiz
- School of Biosciences, Geoffrey Pope Building, University of Exeter, Exeter EX4 4QD, UK
| | - Therese Oskarsson
- Carlsberg Laboratory, Department of Yeast Genetics, Gamle Carlsberg Vej 10, DK-1799, Copenhagen V, Denmark
| | - Katja Schäfer
- Department of Genetics, Edificio Gregor Mendel, Planta 1. Campus de Rabanales, University of Cordoba, 14071 Cordoba, Spain
| | - Lisa Wasserstrom
- Carlsberg Laboratory, Department of Yeast Genetics, Gamle Carlsberg Vej 10, DK-1799, Copenhagen V, Denmark
| | - Axel A Brakhage
- Department of Molecular and Applied Microbiology, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute (HKI), Beutembergstr. 11a, 07745 Jena, Germany; Department of Microbiology and Molecular Biology, Institute of Microbiology, Friedrich Schiller University Jena, Beutenbergstr. 11a, 07745 Jena, Germany
| | - Neil A R Gow
- Aberdeen Fungal Group, School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | - Regine Kahmann
- Max-Planck-Institute for Terrestrial Microbiology, Department of Organismic Interactions, Karl-von-Frisch-Strasse 10, D-35043 Marburg, Germany
| | - Marc-Henri Lebrun
- Evolution and Genomics of Plant Pathogen Interactions, UR 1290 INRA, BIOGER-CPP, Campus AgroParisTech, 78850 Thiverval-Grignon, France
| | - José Perez-Martin
- Instituto de Biología Funcional y GenómicaCSIC, Universidad de Salamanca, 37007 Salamanca, Spain
| | - Antonio Di Pietro
- Department of Genetics, Edificio Gregor Mendel, Planta 1. Campus de Rabanales, University of Cordoba, 14071 Cordoba, Spain
| | - Nicholas J Talbot
- School of Biosciences, Geoffrey Pope Building, University of Exeter, Exeter EX4 4QD, UK
| | - Valerie Toquin
- Biochemistry Department, Bayer SAS, Bayer CropScience, CRLD, 69263 Lyon, France
| | - Andrea Walther
- Carlsberg Laboratory, Department of Yeast Genetics, Gamle Carlsberg Vej 10, DK-1799, Copenhagen V, Denmark
| | - Jürgen Wendland
- Carlsberg Laboratory, Department of Yeast Genetics, Gamle Carlsberg Vej 10, DK-1799, Copenhagen V, Denmark
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Stewart EL, McDonald BA. Measuring quantitative virulence in the wheat pathogen Zymoseptoria tritici using high-throughput automated image analysis. PHYTOPATHOLOGY 2014; 104:985-92. [PMID: 24624955 DOI: 10.1094/phyto-11-13-0328-r] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Zymoseptoria tritici, causal agent of Septoria tritici blotch on wheat, produces pycnidia in chlorotic and necrotic lesions on infected leaves. A high-throughput phenotyping method was developed based on automated digital image analysis that accurately measures the percentage of leaf area covered by lesions (PLACL) as well as pycnidia size and number. A seedling inoculation assay was conducted using 361 Z. tritici isolates originating from a controlled cross and two different winter wheat cultivars. Pycnidia size and density were found to be quantitative traits that showed a continuous distribution in the progeny. There was a weak correlation between pycnidia density and size (r = -0.27) and between pycnidia density and PLACL (r = 0.37). There were significant differences in PLACL and pycnidia density on resistant and susceptible cultivars. In all, >20% of the offspring exhibited significantly different pycnidia density on the two cultivars, consistent with host specialization. Automated image analysis provided greater accuracy and precision compared with traditional visual estimates of virulence. These results show that digital image analysis provides a powerful tool for measuring differences in quantitative virulence among strains of Z. tritici.
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Gautier A, Marcel TC, Confais J, Crane C, Kema G, Suffert F, Walker AS. Development of a rapid multiplex SSR genotyping method to study populations of the fungal plant pathogen Zymoseptoria tritici. BMC Res Notes 2014; 7:373. [PMID: 24943709 PMCID: PMC4074386 DOI: 10.1186/1756-0500-7-373] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Accepted: 05/30/2014] [Indexed: 11/29/2022] Open
Abstract
Background Zymoseptoria tritici is a hemibiotrophic ascomycete fungus causing leaf blotch of wheat that often decreases yield severely. Populations of the fungus are known to be highly diverse and poorly differentiated from each other. However, a genotyping tool is needed to address further questions in large collections of isolates, regarding regional population structure, adaptation to anthropogenic selective pressures, and dynamics of the recently discovered accessory chromosomes. This procedure is limited by costly and time-consuming simplex PCR genotyping. Recent development of genomic approaches and of larger sets of SSRs enabled the optimization of microsatellite multiplexing. Findings We report here a reliable protocol to amplify 24 SSRs organized in three multiplex panels, and covering all Z. tritici chromosomes. We also propose an automatic allele assignment procedure, which allows scoring alleles in a repeatable manner across studies and laboratories. All together, these tools enabled us to characterize local and worldwide populations and to calculate diversity indexes consistent with results reported in the literature. Conclusion This easy-to-use, accurate, repeatable, economical, and faster technical strategy can provide useful genetic information for evolutionary inferences concerning Z. tritici populations. Moreover, it will facilitate the comparison of studies from different scientific groups.
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Affiliation(s)
| | | | | | | | | | | | - Anne-Sophie Walker
- UR 1290 BIOGER-CPP, INRA, BP01, Avenue Lucien Brétignières, F-78850 Thiverval-Grignon, France.
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Gurung S, Short DPG, Atallah ZK, Subbarao KV. Clonal expansion of Verticillium dahliae in lettuce. PHYTOPATHOLOGY 2014; 104:641-9. [PMID: 24476528 DOI: 10.1094/phyto-10-13-0282-r] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Few studies in population biology have documented how structure and diversity of pathogens evolve over time at local scales. With the historical samples of Verticillium dahliae available from lettuce, we investigated the structure and diversity of this pathogen in time and space. Three hundred twenty-nine V. dahliae isolates from lettuce fields collected over 18 years were characterized with polymorphic microsatellite markers and polymerase chain reaction tests for race and mating type. Genetic variation within and among commercial lettuce fields in a single season was also investigated using an additional 146 isolates. Sixty-two haplotypes (HTs) were observed among the 329 isolates. A single HT was frequently observed over multiple years and locations (61.40%). Genetic diversity, allelic richness, and private allelic richness suggested a relatively recent clonal expansion. Race 1 (93.63%) and MAT1-2-1 (99.69%) were overwhelmingly represented among the isolates. Linkage disequilibrium was significant (P < 0.001) for all populations, suggesting limited sexual recombination in the sampled populations from lettuce. Populations from 2006, 2009, and 2010 had higher numbers of unique HTs, implying a recent introduction of novel HTs. We conclude that V. dahliae population from lettuce evaluated in this study is expanding clonally, consistent with an asexually reproducing pathogen, and the movement of clonal genotypes locally occurs over time.
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hassine AB, Hamada W. First isolation of the
Mycosphaerella graminicola
teleomorph stage causing Septoria leaf blotch on wheat in Tunisia. ACTA ACUST UNITED AC 2014. [DOI: 10.5197/j.2044-0588.2014.029.018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Affiliation(s)
- A. Ben hassine
- Laboratory of Genetics and Plant BreedingInstitut National Agronomique de Tunisie 43Avenue Charles Nicolle1082TunisMahrajèneTunisia
| | - W. Hamada
- Laboratory of Genetics and Plant BreedingInstitut National Agronomique de Tunisie 43Avenue Charles Nicolle1082TunisMahrajèneTunisia
- Higher School of Agriculture of Kef (ESAK)Boulifa7119kefTunisia
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Bihon W, Wingfield MJ, Slippers B, Duong TA, Wingfield BD. MAT gene idiomorphs suggest a heterothallic sexual cycle in a predominantly asexual and important pine pathogen. Fungal Genet Biol 2014; 62:55-61. [DOI: 10.1016/j.fgb.2013.10.013] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Revised: 10/30/2013] [Accepted: 10/31/2013] [Indexed: 10/26/2022]
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Maciel JLN, Ceresini PC, Castroagudin VL, Zala M, Kema GHJ, McDonald BA. Population structure and pathotype diversity of the wheat blast pathogen Magnaporthe oryzae 25 years after its emergence in Brazil. PHYTOPATHOLOGY 2014; 104:95-107. [PMID: 23901831 DOI: 10.1094/phyto-11-12-0294-r] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Since its first report in Brazil in 1985, wheat blast, caused by Magnaporthe oryzae (anamorph: Pyricularia oryzae), has become increasingly important in South America, where the disease is still spreading. We used 11 microsatellite loci to elucidate the population structure of the wheat blast pathogen in wheat fields in central-western, southeastern, and southern Brazil. No subdivision was found among the wheat-infecting populations, consistent with high levels of gene flow across a large spatial scale. Although the clonal fraction was relatively high and the two mating type idiomorphs (MAT1-1 and MAT1-2) were not at similar frequencies, the clone-corrected populations from Distrito Federal and Goiás, Minas Triangle, and São Paulo were in gametic equilibrium. Based on these findings, we propose that populations of the wheat blast pathogen exhibit a mixed reproductive system in which sexual reproduction is followed by the local dispersal of clones. Seedling virulence assays with local wheat cultivars differentiated 14 pathotypes in the current population. Detached head virulence assays differentiated eight virulence groups on the same wheat cultivars. There was no correlation between seedling and head reactions.
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Nieuwenhuis BPS, Aanen DK. Sexual selection in fungi. J Evol Biol 2013; 25:2397-411. [PMID: 23163326 DOI: 10.1111/jeb.12017] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2012] [Revised: 09/07/2012] [Accepted: 09/07/2012] [Indexed: 12/14/2022]
Abstract
The significance of sexual selection, the component of natural selection associated with variation in mating success, is well established for the evolution of animals and plants, but not for the evolution of fungi. Even though fungi do not have separate sexes, most filamentous fungi mate in a hermaphroditic fashion, with distinct sex roles, that is, investment in large gametes (female role) and fertilization by other small gametes (male role). Fungi compete to fertilize, analogous to 'male-male' competition, whereas they can be selective when being fertilized, analogous to female choice. Mating types, which determine genetic compatibility among fungal gametes, are important for sexual selection in two respects. First, genes at the mating-type loci regulate different aspects of mating and thus can be subject to sexual selection. Second, for sexual selection, not only the two sexes (or sex roles) but also the mating types can form the classes, the members of which compete for access to members of the other class. This is significant if mating-type gene products are costly, thus signalling genetic quality according to Zahavi's handicap principle. We propose that sexual selection explains various fungal characteristics such as the observed high redundancy of pheromones at the B mating-type locus of Agaricomycotina, the occurrence of multiple types of spores in Ascomycotina or the strong pheromone signalling in yeasts. Furthermore, we argue that fungi are good model systems to experimentally study fundamental aspects of sexual selection, due to their fast generation times and high diversity of life cycles and mating systems.
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Affiliation(s)
- B P S Nieuwenhuis
- Laboratory of Genetics, Wageningen University, Wageningen, The Netherlands.
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Gurung S, Short D, Adhikari T. Global population structure and migration patterns suggest significant population differentiation among isolates of Pyrenophora tritici-repentis. Fungal Genet Biol 2013; 52:32-41. [DOI: 10.1016/j.fgb.2013.01.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Revised: 01/05/2013] [Accepted: 01/17/2013] [Indexed: 11/28/2022]
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Wilken PM, Steenkamp ET, Hall TA, de Beer ZW, Wingfield MJ, Wingfield BD. Both mating types in the heterothallic fungus Ophiostoma quercus contain MAT1-1 and MAT1-2 genes. Fungal Biol 2012; 116:427-37. [DOI: 10.1016/j.funbio.2012.01.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Revised: 01/02/2012] [Accepted: 01/05/2012] [Indexed: 10/14/2022]
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48
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Bolton MD, Secor GA, Rivera V, Weiland JJ, Rudolph K, Birla K, Rengifo J, Campbell LG. Evaluation of the potential for sexual reproduction in field populations of Cercospora beticola from USA. Fungal Biol 2012; 116:511-21. [PMID: 22483049 DOI: 10.1016/j.funbio.2012.01.011] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2011] [Revised: 01/19/2012] [Accepted: 01/24/2012] [Indexed: 02/04/2023]
Abstract
Cercospora leaf spot, caused by the hemibiotrophic fungal pathogen Cercospora beticola, is the most economically damaging foliar disease of sugarbeet worldwide. Although most C. beticola populations display characteristics reminiscent of sexual recombination, no teleomorph has been described. To assess whether populations in northern United States have characteristics consistent with sexual reproduction, 1024 isolates collected over a 3-y period were analyzed for frequency and distribution of mating type genes. After clone correction, an approximately equal distribution of mating types was found for each sampling year. Mating type frequency was also assessed in individual lesions. Lesions always consisted of isolates with a single mating type and microsatellite haplotype, but both mating types and up to five microsatellite haplotypes could be found on an individual leaf. The MAT1-1-1 and MAT1-2-1 genes were sequenced from 28 MAT1-1 and 28 MAT1-2 isolates, respectively. Three MAT1-1-1 nucleotide haplotypes were identified that encoded a single amino acid sequence. For MAT1-2-1, five nucleotide haplotypes were identified that encoded four protein variants. MAT1-1-1 and MAT1-2-1 gene expression analyses were conducted on plants inoculated with either or both mating types. MAT1-1-1 expression remained low, but MAT1-2-1 spiked during late stages of colonization. A segment of the MAT1-2-1 coding sequence was also found in MAT1-1 isolates. Taken together, these results suggest that C. beticola has the potential for sexual reproduction.
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Affiliation(s)
- Melvin D Bolton
- United States Department of Agriculture - Agricultural Research Service, Northern Crops Science Laboratory, Fargo, ND 58102-2765, USA.
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49
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Torriani SFF, Stukenbrock EH, Brunner PC, McDonald BA, Croll D. Evidence for extensive recent intron transposition in closely related fungi. Curr Biol 2011; 21:2017-22. [PMID: 22100062 DOI: 10.1016/j.cub.2011.10.041] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Revised: 10/26/2011] [Accepted: 10/26/2011] [Indexed: 11/30/2022]
Abstract
Though spliceosomal introns are a major structural component of most eukaryotic genes and intron density varies by more than three orders of magnitude among eukaryotes [1-3], the origins of introns are poorly understood, and only a few cases of unambiguous intron gain are known [4-8]. We utilized population genomic comparisons of three closely related fungi to identify crucial transitory phases of intron gain and loss. We found 74 intron positions showing intraspecific presence-absence polymorphisms (PAPs) for the entire intron. Population genetic analyses identified intron PAPs at different stages of fixation and showed that intron gain or loss was very recent. We found direct support for extensive intron transposition among unrelated genes. A substantial proportion of highly similar introns in the genome either were recently gained or showed a transient phase of intron PAP. We also identified an intron transfer among paralogous genes that created a new intron. Intron loss was due mainly to homologous recombination involving reverse-transcribed mRNA. The large number of intron positions in transient phases of either intron gain or loss shows that intron evolution is much faster than previously thought and provides an excellent model to study molecular mechanisms of intron gain.
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Affiliation(s)
- Stefano F F Torriani
- Institute of Integrative Biology, Swiss Federal Institute of Technology (ETH Zurich), 8092 Zurich, Switzerland
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50
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Stukenbrock EH, Bataillon T, Dutheil JY, Hansen TT, Li R, Zala M, McDonald BA, Wang J, Schierup MH. The making of a new pathogen: insights from comparative population genomics of the domesticated wheat pathogen Mycosphaerella graminicola and its wild sister species. Genome Res 2011; 21:2157-66. [PMID: 21994252 DOI: 10.1101/gr.118851.110] [Citation(s) in RCA: 159] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The fungus Mycosphaerella graminicola emerged as a new pathogen of cultivated wheat during its domestication ~11,000 yr ago. We assembled 12 high-quality full genome sequences to investigate the genetic footprints of selection in this wheat pathogen and closely related sister species that infect wild grasses. We demonstrate a strong effect of natural selection in shaping the pathogen genomes with only ~3% of nonsynonymous mutations being effectively neutral. Forty percent of all fixed nonsynonymous substitutions, on the other hand, are driven by positive selection. Adaptive evolution has affected M. graminicola to the highest extent, consistent with recent host specialization. Positive selection has prominently altered genes encoding secreted proteins and putative pathogen effectors supporting the premise that molecular host-pathogen interaction is a strong driver of pathogen evolution. Recent divergence between pathogen sister species is attested by the high degree of incomplete lineage sorting (ILS) in their genomes. We exploit ILS to generate a genetic map of the species without any crossing data, document recent times of species divergence relative to genome divergence, and show that gene-rich regions or regions with low recombination experience stronger effects of natural selection on neutral diversity. Emergence of a new agricultural host selected a highly specialized and fast-evolving pathogen with unique evolutionary patterns compared with its wild relatives. The strong impact of natural selection, we document, is at odds with the small effective population sizes estimated and suggest that population sizes were historically large but likely unstable.
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Affiliation(s)
- Eva H Stukenbrock
- Bioinformatics Research Center, Aarhus University, C.F. Moellers Alle, DK-8000 Aarhus C, Denmark.
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