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Timilsina S, Kaur A, Sharma A, Ramamoorthy S, Vallad GE, Wang N, White FF, Potnis N, Goss EM, Jones JB. Xanthomonas as a Model System for Studying Pathogen Emergence and Evolution. PHYTOPATHOLOGY 2024:PHYTO03240084RVW. [PMID: 38648116 DOI: 10.1094/phyto-03-24-0084-rvw] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/25/2024]
Abstract
In this review, we highlight studies in which whole-genome sequencing, comparative genomics, and population genomics have provided unprecedented insights into past and ongoing pathogen evolution. These include new understandings of the adaptive evolution of secretion systems and their effectors. We focus on Xanthomonas pathosystems that have seen intensive study and improved our understanding of pathogen emergence and evolution, particularly in the context of host specialization: citrus canker, bacterial blight of rice, and bacterial spot of tomato and pepper. Across pathosystems, pathogens appear to follow a pattern of bursts of evolution and diversification that impact host adaptation. There remains a need for studies on the mechanisms of host range evolution and genetic exchange among closely related but differentially host-specialized species and to start moving beyond the study of specific strain and host cultivar pairwise interactions to thinking about these pathosystems in a community context.
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Affiliation(s)
- Sujan Timilsina
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611
| | - Amandeep Kaur
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611
| | - Anuj Sharma
- Department of Horticultural Sciences, Gulf Coast Research and Education Center, University of Florida, Wimauma, FL 33598
| | | | - Gary E Vallad
- Department of Plant Pathology, Gulf Coast Research and Education Center, University of Florida, Wimauma, FL 33598
| | - Nian Wang
- Department of Microbiology and Cell Science, Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850
| | - Frank F White
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611
| | - Neha Potnis
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL 36849
| | - Erica M Goss
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611
- Emerging Pathogens Institute, University of Florida, Gainesville, FL 32610
| | - Jeffrey B Jones
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611
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Chen JR, Aguirre-Carvajal K, Xue DY, Chang HC, Arone-Maxwell L, Lin YP, Armijos-Jaramillo V, Oliva R. Exploring the genetic makeup of Xanthomonas species causing bacterial spot in Taiwan: evidence of population shift and local adaptation. Front Microbiol 2024; 15:1408885. [PMID: 38846563 PMCID: PMC11153759 DOI: 10.3389/fmicb.2024.1408885] [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: 03/29/2024] [Accepted: 05/13/2024] [Indexed: 06/09/2024] Open
Abstract
The introduction of plant pathogens can quickly reshape disease dynamics in island agro-ecologies, representing a continuous challenge for local crop management strategies. Xanthomonas pathogens causing tomato bacterial spot were probably introduced in Taiwan several decades ago, creating a unique opportunity to study the genetic makeup and adaptive response of this alien population. We examined the phenotypic and genotypic identity of 669 pathogen entries collected across different regions of Taiwan in the last three decades. The analysis detected a major population shift, where X. euvesicatoria and X. vesicatoria races T1 and T2 were replaced by new races of X. perforans. After its introduction, race T4 quickly became dominant in all tomato-growing areas of the island. The genomic analysis of 317 global genomes indicates that the Xanthomonas population in Taiwan has a narrow genetic background, most likely resulting from a small number of colonization events. However, despite the apparent genetic uniformity, X. perforans race T4 shows multiple phenotypic responses in tomato lines. Additionally, an in-depth analysis of effector composition suggests diversification in response to local adaptation. These include unique mutations on avrXv3 which might allow the pathogen to overcome Xv3/Rx4 resistance gene. The findings underscore the dynamic evolution of a pathogen when introduced in a semi-isolated environment and provide insights into the potential management strategies for this important disease of tomato.
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Affiliation(s)
- Jaw-Rong Chen
- Safe and Sustainable Value Chain, World Vegetable Center, Shanhua, Taiwan
| | - Kevin Aguirre-Carvajal
- Research Center of Information and Communication Technologies, University of A Coruña, A Coruña, Spain
- Bio-Cheminformatics Research Group, Universidad de Las Américas, Quito, Ecuador
| | - Dao-Yuan Xue
- Seed and Seedling Management Section, Taiwan Seed Improvement and Propagation Station, Ministry of Agriculture, Taichung, Taiwan
| | - Hung-Chia Chang
- Safe and Sustainable Value Chain, World Vegetable Center, Shanhua, Taiwan
| | | | - Ya-Ping Lin
- Safe and Sustainable Value Chain, World Vegetable Center, Shanhua, Taiwan
| | - Vinicio Armijos-Jaramillo
- Bio-Cheminformatics Research Group, Universidad de Las Américas, Quito, Ecuador
- Facultad de Ingeniería y Ciencias Aplicadas, Universidad de Las Américas, Quito, Ecuador
| | - Ricardo Oliva
- Safe and Sustainable Value Chain, World Vegetable Center, Shanhua, Taiwan
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Sharma A, Timilsina S, Abrahamian P, Minsavage GV, Jones JB, Vallad GE, Goss EM. Bacterial Mutation During Seasonal Epidemics. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2024; 37:93-97. [PMID: 38105425 DOI: 10.1094/mpmi-10-23-0164-sc] [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: 12/19/2023]
Abstract
Rapidly evolving bacterial pathogens pose a unique challenge for long-term plant disease management. In this study, we investigated the types and rate of mutations in bacterial populations during seasonal disease epidemics. Two phylogenetically distinct strains of the bacterial spot pathogen, Xanthomonas perforans, were marked, released in tomato fields, and recaptured at several time points during the growing season. Genomic variations in recaptured isolates were identified by comparative analysis of their whole-genome sequences. In total, 180 unique variations (116 substitutions, 57 insertions/deletions, and 7 structural variations) were identified from 300 genomes, resulting in the overall host-associated mutation rate of ∼0.3 to 0.9/genome/week. This result serves as a benchmark for bacterial mutation during epidemics in similar pathosystems. [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)
- Anuj Sharma
- Department of Plant Pathology, University of Florida, Gainesville, FL, U.S.A
- Gulf Coast Research and Education Center, University of Florida, Wimauma, FL, U.S.A
| | - Sujan Timilsina
- Department of Plant Pathology, University of Florida, Gainesville, FL, U.S.A
| | - Peter Abrahamian
- Gulf Coast Research and Education Center, University of Florida, Wimauma, FL, U.S.A
| | - Gerald V Minsavage
- Department of Plant Pathology, University of Florida, Gainesville, FL, U.S.A
| | - Jeffrey B Jones
- Department of Plant Pathology, University of Florida, Gainesville, FL, U.S.A
| | - Gary E Vallad
- Gulf Coast Research and Education Center, University of Florida, Wimauma, FL, U.S.A
| | - Erica M Goss
- Department of Plant Pathology, University of Florida, Gainesville, FL, U.S.A
- Emerging Pathogens Institute, University of Florida, Gainesville, FL, U.S.A
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Subedi A, Nga NTT, Tien DTK, Minsavage GV, Roberts PD, Goss EM, Jones JB. Draft genomes announcement of Vietnamese Xanthomonas euvesicatoria strains causing bacterial spot on pepper. Access Microbiol 2024; 6:000741.v3. [PMID: 38361655 PMCID: PMC10866037 DOI: 10.1099/acmi.0.000741.v3] [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: 11/17/2023] [Accepted: 01/05/2024] [Indexed: 02/17/2024] Open
Abstract
Xanthomonas euvesicatoria the primary causal agent of bacterial spot of pepper (BSP), poses a significant global challenge, resulting in severe defoliation and yield losses for pepper growers. We present the whole genome sequences of eight X. euvesicatoria strains associated with BSP in Vietnam. These genomes contribute to representation of pepper production regions in the global sample of X. euvesicatoria genomes, enabling the development of precise global disease management strategies.
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Affiliation(s)
- Aastha Subedi
- Department of Plant Pathology, University of Florida, Gainesville, Florida, USA
| | - Nguyen Thi Thu Nga
- Department of Plant Protection, College of Agriculture, Can Tho University, Can Tho City, Vietnam
| | - Doan Thi Kieu Tien
- Department of Plant Protection, College of Agriculture, Can Tho University, Can Tho City, Vietnam
| | - Gerald V. Minsavage
- Department of Plant Pathology, University of Florida, Gainesville, Florida, USA
| | - Pamela D. Roberts
- Southwest Florida Research & Education Center, University of Florida, Immokalee, Florida, USA
| | - Erica M. Goss
- Department of Plant Pathology, University of Florida, Gainesville, Florida, USA
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida, USA
| | - Jeffrey B. Jones
- Department of Plant Pathology, University of Florida, Gainesville, Florida, USA
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Subedi A, Barrera LBTDL, Ivey ML, Egel DS, Kebede M, Kara S, Aysan Y, Minsavage GV, Roberts PD, Jones JB, Goss EM. Population Genomics Reveals an Emerging Lineage of Xanthomonas perforans on Pepper. PHYTOPATHOLOGY 2024; 114:241-250. [PMID: 37432099 DOI: 10.1094/phyto-04-23-0128-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: 07/12/2023]
Abstract
Xanthomonas perforans-the dominant causal agent of bacterial leaf spot of tomato-is an emerging pathogen of pepper, indicative of a potential host expansion across the southeastern United States. However, studies of the genetic diversity and evolution of X. perforans from pepper remain limited. In this study, the whole-genome sequences of 35 X. perforans strains isolated from pepper from four fields and two transplant facilities across southwest Florida between 2019 and 2021 were used to compare genomic divergence, evolution, and variation in type III secreted effectors. Phylogenetic analysis based on core genes revealed that all 35 X. perforans strains formed one genetic cluster with pepper and tomato strains from Alabama and Turkey and were closely related to strains isolated from tomato in Indiana, Mexico, and Louisiana. The in planta population growth of tomato strains isolated from Indiana, Mexico, Louisiana, and Turkey in pepper leaf mesophyll was on par with pepper X. perforans and X. euvesicatoria strains. Molecular clock analysis of the 35 Florida strains dated their emergence to approximately 2017. While strains varied in copper tolerance, all sequenced strains harbored the avrHah1 transcription activation-like effector located on a conjugative plasmid, not previously reported in Florida. Our findings suggest that there is a geographically distributed lineage of X. perforans strains on tomato that has the genetic background to cause disease on pepper. Moreover, this study clarifies potential adaptive variants of X. perforans on pepper that could help forecast the emergence of such strains and enable immediate or preemptive intervention.
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Affiliation(s)
- Aastha Subedi
- Department of Plant Pathology, University of Florida, Gainesville, FL, U.S.A
| | | | - Melanie Lewis Ivey
- Department of Plant Pathology, The Ohio State University, Wooster, OH, U.S.A
| | - Daniel S Egel
- Botany and Plant Pathology Department, Purdue University, West Lafayette, IN, U.S.A
| | - Misrak Kebede
- Biotechnology Department, Collage of Biological and Chemical Engineering, Addis Ababa Science and Technology University, Addis Ababa, Ethiopia
| | - Serhat Kara
- Alata Horticulture Research Institute, Mersin, Turkey
| | - Yesim Aysan
- Department of Plant Protection, Cukurova University, Adana, Turkey
| | - Gerald V Minsavage
- Department of Plant Pathology, University of Florida, Gainesville, FL, U.S.A
| | - Pamela D Roberts
- Southwest Florida Research & Education Center, University of Florida, Immokalee, FL, U.S.A
| | - Jeffrey B Jones
- Department of Plant Pathology, University of Florida, Gainesville, FL, U.S.A
| | - Erica M Goss
- Department of Plant Pathology, University of Florida, Gainesville, FL, U.S.A
- Emerging Pathogens Institute, University of Florida, Gainesville, FL, U.S.A
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Subedi A, Minsavage GV, Jones JB, Goss EM, Roberts PD. Exploring Diversity of Bacterial Spot Associated Xanthomonas Population of Pepper in Southwest Florida. PLANT DISEASE 2023; 107:2978-2985. [PMID: 36856653 DOI: 10.1094/pdis-10-22-2484-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: 06/18/2023]
Abstract
Bacterial spot caused by Xanthomonas spp. is a significant disease that challenges pepper growers worldwide and is particularly severe in a hot and humid environment. Understanding the pathogen's population biology is critical for sustainable disease management. The goal of this study was to characterize the species, race, and bactericide sensitivity of bacterial spot-associated Xanthomonas collected from pepper in Florida. A survey of pepper production fields in southwest Florida between 2019 and 2021-covering two counties, eight farms, and two transplant facilities-resulted in the isolation of 542 Xanthomonas euvesicatoria and 35 Xanthomonas perforans strains. Four races were identified on pepper, of which most strains were race P1 (42%), race P6 (26%), race P3 (24%), and less common was race P4 (8%). All X. perforans strains were characterized as race P1 and showed a compatible reaction on tomato. Sixty-two and 96% of strains were sensitive to copper sulfate and streptomycin, respectively. One farm that did not use copper to manage the disease contained only copper-sensitive strains and was the only farm with race P3 strains. Strains were assayed for starch hydrolysis activity of which a third of X. euvesicatoria strains were strongly amylolytic, a characteristic not typically observed in X. euvesicatoria. All X. perforans strains produced bacteriocins against X. euvesicatoria in vitro. The Xanthomonas population causing bacterial spot on pepper in southwest Florida is diverse and dynamic; thus, regular monitoring provides pertinent information to plant breeders and growers for designing disease management strategies.
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Affiliation(s)
- Aastha Subedi
- Department of Plant Pathology, University of Florida, Gainesville, FL
| | | | - Jeffrey B Jones
- Department of Plant Pathology, University of Florida, Gainesville, FL
| | - Erica M Goss
- Department of Plant Pathology, University of Florida, Gainesville, FL
- Emerging Pathogens Institute, University of Florida, Gainesville, FL
| | - Pamela D Roberts
- Southwest Florida Research and Education Center, University of Florida, Immokalee, FL
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Shikov AE, Savina IA, Nizhnikov AA, Antonets KS. Recombination in Bacterial Genomes: Evolutionary Trends. Toxins (Basel) 2023; 15:568. [PMID: 37755994 PMCID: PMC10534446 DOI: 10.3390/toxins15090568] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 09/02/2023] [Accepted: 09/07/2023] [Indexed: 09/28/2023] Open
Abstract
Bacterial organisms have undergone homologous recombination (HR) and horizontal gene transfer (HGT) multiple times during their history. These processes could increase fitness to new environments, cause specialization, the emergence of new species, and changes in virulence. Therefore, comprehensive knowledge of the impact and intensity of genetic exchanges and the location of recombination hotspots on the genome is necessary for understanding the dynamics of adaptation to various conditions. To this end, we aimed to characterize the functional impact and genomic context of computationally detected recombination events by analyzing genomic studies of any bacterial species, for which events have been detected in the last 30 years. Genomic loci where the transfer of DNA was detected pertained to mobile genetic elements (MGEs) housing genes that code for proteins engaged in distinct cellular processes, such as secretion systems, toxins, infection effectors, biosynthesis enzymes, etc. We found that all inferences fall into three main lifestyle categories, namely, ecological diversification, pathogenesis, and symbiosis. The latter primarily exhibits ancestral events, thus, possibly indicating that adaptation appears to be governed by similar recombination-dependent mechanisms.
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Affiliation(s)
- Anton E. Shikov
- Laboratory for Proteomics of Supra-Organismal Systems, All-Russia Research Institute for Agricultural Microbiology (ARRIAM), 196608 St. Petersburg, Russia; (A.E.S.); (I.A.S.); (A.A.N.)
- Faculty of Biology, St. Petersburg State University (SPbSU), 199034 St. Petersburg, Russia
| | - Iuliia A. Savina
- Laboratory for Proteomics of Supra-Organismal Systems, All-Russia Research Institute for Agricultural Microbiology (ARRIAM), 196608 St. Petersburg, Russia; (A.E.S.); (I.A.S.); (A.A.N.)
| | - Anton A. Nizhnikov
- Laboratory for Proteomics of Supra-Organismal Systems, All-Russia Research Institute for Agricultural Microbiology (ARRIAM), 196608 St. Petersburg, Russia; (A.E.S.); (I.A.S.); (A.A.N.)
- Faculty of Biology, St. Petersburg State University (SPbSU), 199034 St. Petersburg, Russia
| | - Kirill S. Antonets
- Laboratory for Proteomics of Supra-Organismal Systems, All-Russia Research Institute for Agricultural Microbiology (ARRIAM), 196608 St. Petersburg, Russia; (A.E.S.); (I.A.S.); (A.A.N.)
- Faculty of Biology, St. Petersburg State University (SPbSU), 199034 St. Petersburg, Russia
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Agarwal V, Stubits R, Nassrullah Z, Dillon MM. Pangenome insights into the diversification and disease specificity of worldwide Xanthomonas outbreaks. Front Microbiol 2023; 14:1213261. [PMID: 37476668 PMCID: PMC10356107 DOI: 10.3389/fmicb.2023.1213261] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Accepted: 06/15/2023] [Indexed: 07/22/2023] Open
Abstract
The bacterial genus Xanthomonas is responsible for disease outbreaks in several hundred plant species, many of them economically important crops. In the era of next-generation sequencing, thousands of strains from this genus have now been sequenced as part of isolated studies that focus on outbreak characterization, host range, diversity, and virulence factor identification. However, these data have not been synthesized and we lack a comprehensive phylogeny for the genus, with some species designations in public databases still relying on phenotypic similarities and representative sequence typing. The extent of genetic cohesiveness among Xanthomonas strains, the distribution of virulence factors across strains, and the impact of evolutionary history on host range across the genus are also poorly understood. In this study, we present a pangenome analysis of 1,910 diverse Xanthomonas genomes, highlighting their evolutionary relationships, the distribution of virulence-associated genes across strains, and rates of horizontal gene transfer. We find a number of broadly conserved classes of virulence factors and considerable diversity in the Type 3 Secretion Systems (T3SSs) and Type 3 Secreted Effector (T3SE) repertoires of different Xanthomonas species. We also use these data to re-assign incorrectly classified strains to phylogenetically informed species designations and find evidence of both monophyletic host specificity and convergent evolution of phylogenetically distant strains to the same host. Finally, we explore the role of recombination in maintaining genetic cohesion within the Xanthomonas genus as a result of both ancestral and recent recombination events. Understanding the evolutionary history of Xanthomonas species and the relationship of key virulence factors with host-specificity provides valuable insight into the mechanisms through which Xanthomonas species shift between hosts and will enable us to develop more robust resistance strategies against these highly virulent pathogens.
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Affiliation(s)
- Viplav Agarwal
- Department of Biology, University of Toronto Mississauga, Mississauga, ON, Canada
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada
| | - Rachel Stubits
- Department of Biology, University of Toronto Mississauga, Mississauga, ON, Canada
| | - Zain Nassrullah
- Department of Biology, University of Toronto Mississauga, Mississauga, ON, Canada
| | - Marcus M. Dillon
- Department of Biology, University of Toronto Mississauga, Mississauga, ON, Canada
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada
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Subedi A, Kara S, Aysan Y, Minsavage GV, Timilsina S, Roberts PD, Goss EM, Jones JB. Draft genome sequences of 11 Xanthomonas strains associated with bacterial spot disease in Turkey. Access Microbiol 2023; 5:acmi000586.v3. [PMID: 37424560 PMCID: PMC10323804 DOI: 10.1099/acmi.0.000586.v3] [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: 02/21/2023] [Accepted: 05/12/2023] [Indexed: 07/11/2023] Open
Abstract
Bacterial spot is an economically significant disease in tomato and pepper-producing countries globally. We report the whole-genome sequence of 11 Xanthomonas strains associated with bacterial spot disease on pepper, tomato and eggplant in the Southeastern Anatolia Region, Turkey. This genomic information can be used as a reference to study the genetic diversity of these species and contribute to illuminating pathogen evolution with respect to host specificity.
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Affiliation(s)
- Aastha Subedi
- Department of Plant Pathology, University of Florida, Gainesville, Florida, USA
| | - Serhat Kara
- Alata Horticulture Research Institute, Mersin, Turkey
| | - Yesim Aysan
- Department of Plant Protection, Cukurova University, Adana, Turkey
| | - Gerald V. Minsavage
- Department of Plant Pathology, University of Florida, Gainesville, Florida, USA
| | - Sujan Timilsina
- Department of Plant Pathology, University of Florida, Gainesville, Florida, USA
| | - Pamela D. Roberts
- Southwest Florida Research & Education Center, University of Florida, Immokalee, Florida, USA
| | - Erica M. Goss
- Department of Plant Pathology, University of Florida, Gainesville, Florida, USA
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida, USA
| | - Jeffrey B. Jones
- Department of Plant Pathology, University of Florida, Gainesville, Florida, USA
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Castillo AI, Almeida RPP. The Multifaceted Role of Homologous Recombination in a Fastidious Bacterial Plant Pathogen. Appl Environ Microbiol 2023; 89:e0043923. [PMID: 37154680 PMCID: PMC10231230 DOI: 10.1128/aem.00439-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Accepted: 04/17/2023] [Indexed: 05/10/2023] Open
Abstract
Homologous recombination plays a key function in the evolution of bacterial genomes. Within Xylella fastidiosa, an emerging plant pathogen with increasing host and geographic ranges, it has been suggested that homologous recombination facilitates host switching, speciation, and the development of virulence. We used 340 whole-genome sequences to study the relationship between inter- and intrasubspecific homologous recombination, random mutation, and natural selection across individual X. fastidiosa genes. Individual gene orthologs were identified and aligned, and a maximum likelihood (ML) gene tree was generated. Each gene alignment and tree pair were then used to calculate gene-wide and branch-specific r/m values (relative effect of recombination to mutation), gene-wide and branch-site nonsynonymous over synonymous substitution rates (dN/dS values; episodic selection), and branch length (as a proxy for mutation rate). The relationships between these variables were evaluated at the global level (i.e., for all genes among and within a subspecies), among specific functional classes (i.e., COGs), and between pangenome components (i.e., accessory versus core genes). Our analysis showed that r/m varied widely among genes as well as across X. fastidiosa subspecies. While r/m and dN/dS values were positively correlated in some instances (e.g., core genes in X. fastidiosa subsp. fastidiosa and both core and accessory genes in X. fastidiosa subsp. multiplex), low correlation coefficients suggested no clear biological significance. Overall, our results indicate that, in addition to its adaptive role in certain genes, homologous recombination acts as a homogenizing and a neutral force across phylogenetic clades, gene functional groups, and pangenome components. IMPORTANCE There is ample evidence that homologous recombination occurs frequently in the economically important plant pathogen Xylella fastidiosa. Homologous recombination has been known to occur among sympatric subspecies and is associated with host-switching events and virulence-linked genes. As a consequence, is it generally assumed that recombinant events in X. fastidiosa are adaptive. This mindset influences expectations of how homologous recombination acts as an evolutionary force as well as how management strategies for X. fastidiosa diseases are determined. Yet, homologous recombination plays roles beyond that of a source for diversification and adaptation. Homologous recombination can act as a DNA repair mechanism, as a means to facilitate nucleotide compositional change, as a homogenization mechanism within populations, or even as a neutral force. Here, we provide a first assessment of long-held beliefs regarding the general role of recombination in adaptation for X. fastidiosa. We evaluate gene-specific variations in homologous recombination rate across three X. fastidiosa subspecies and its relationship to other evolutionary forces (e.g., natural selection, mutation, etc.). These data were used to assess the role of homologous recombination in X. fastidiosa evolution.
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Affiliation(s)
- Andreina I. Castillo
- Department of Environmental Science, Policy and Management, University of California, Berkeley, California, USA
| | - Rodrigo P. P. Almeida
- Department of Environmental Science, Policy and Management, University of California, Berkeley, California, USA
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11
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Newberry EA, Minsavage GV, Holland A, Jones JB, Potnis N. Genome-Wide Association to Study the Host-Specificity Determinants of Xanthomonas perforans. PHYTOPATHOLOGY 2023; 113:400-412. [PMID: 36318253 DOI: 10.1094/phyto-08-22-0294-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: 06/16/2023]
Abstract
Xanthomonas perforans and X. euvesicatoria are the causal agents of bacterial spot disease of tomato and pepper, endemic to the Southeastern United States. Although very closely related, the two bacterial species differ in host specificity, where X. perforans is the dominant pathogen of tomato and X. euvesicatoria that of pepper. This is in part due to the activity of avirulence proteins that are secreted by X. perforans strains and elicit effector-triggered immunity in pepper leaves, thereby restricting pathogen growth. In recent years, the emergence of several pepper-pathogenic X. perforans lineages has revealed variability within the bacterial species to multiply and cause disease in pepper, even in the absence of avirulence gene activity. Here, we investigated the basal evolutionary processes underlying the host range of this species using multiple genome-wide association analyses. Surprisingly, we identified two novel gene candidates that were significantly associated with pepper-pathogenic X. perforans and X. euvesicatoria. Both candidates were predicted to be involved in the transport/acquisition of nutrients common to the plant cell wall or apoplast and included a TonB-dependent receptor, which was disrupted through independent mutations within the X. perforans lineage. The other included a symporter of protons/glutamate, gltP, enriched with pepper-associated mutations near the promoter and start codon of the gene. Functional analysis of these candidates revealed that only the TonB-dependent receptor had a minor effect on the symptom development and growth of X. perforans in pepper leaves, indicating that pathogenicity to this host might have evolved independently within the bacterial species and is likely a complex, multigenic trait.
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Affiliation(s)
- Eric A Newberry
- Department of Entomology and Plant Pathology, Auburn University, AL 36849
| | | | - Auston Holland
- Department of Entomology and Plant Pathology, Auburn University, AL 36849
| | - Jeffrey B Jones
- Department of Plant Pathology, University of Florida, FL 32611
| | - Neha Potnis
- Department of Entomology and Plant Pathology, Auburn University, AL 36849
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Klein-Gordon JM, Guingab-Cagmat J, Minsavage GV, Meke L, Vallad GE, Goss EM, Garrett TJ, Jones JB. Strength in Numbers: Density-Dependent Volatile-Induced Antimicrobial Activity by Xanthomonas perforans. PHYTOPATHOLOGY 2023; 113:160-169. [PMID: 36129764 DOI: 10.1094/phyto-04-22-0131-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
For most of the 20th century, Xanthomonas euvesicatoria was the only known bacterium associated with bacterial spot of tomato in Florida. X. perforans quickly replaced X. euvesicatoria, mainly because of production of three bacteriocins (BCNs) against X. euvesicatoria; however, X. perforans outcompeted X. euvesicatoria even when the three known BCNs were deleted. Surprisingly, we observed antimicrobial activity against X. euvesicatoria in the BCN triple mutant when the triple mutant was grown in Petri plates containing multiple spots but not in Petri plates containing only one spot. We determined that changes in the headspace composition (i.e., volatiles) rather than a diffusible signal in the agar were required for induction of the antimicrobial activity. Other Xanthomonas species also produced volatile-induced antimicrobial compounds against X. euvesicatoria and elicited antimicrobial activity by X. perforans. A wide range of plant pathogenic bacteria, including Clavibacter michiganensis subsp. michiganensis, Pantoea stewartii, and Pseudomonas cichorii, also elicited antimicrobial activity by X. perforans when multiple spots of the species were present. To identify potential antimicrobial compounds, we performed liquid chromatography with high-resolution mass spectrometry of the agar surrounding the spot in the high cell density Petri plates where the antimicrobial activity was present compared with agar surrounding the spot in Petri plates with one spot where antimicrobial activity was not observed. Among the compounds identified in the zone of inhibition were N-butanoyl-L-homoserine lactone and N-(3-hydroxy-butanoyl)-homoserine lactone, which are known quorum-sensing metabolites in other bacteria.
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Affiliation(s)
- Jeannie M Klein-Gordon
- Department of Plant Pathology, IFAS, University of Florida, Gainesville, FL
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI
| | - Joy Guingab-Cagmat
- Southeast Center for Integrated Metabolomics (SECIM), University of Florida, Gainesville, FL
| | - Gerald V Minsavage
- Department of Plant Pathology, IFAS, University of Florida, Gainesville, FL
| | - Laurel Meke
- Southeast Center for Integrated Metabolomics (SECIM), University of Florida, Gainesville, FL
| | - Gary E Vallad
- Department of Plant Pathology, IFAS, University of Florida, Gainesville, FL
- Gulf Coast Research and Education Center, IFAS, University of Florida, Balm, FL
| | - Erica M Goss
- Department of Plant Pathology, IFAS, University of Florida, Gainesville, FL
- Emerging Pathogens Institute, University of Florida, Gainesville, FL
| | - Timothy J Garrett
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI
- Department of Pathology, Immunology and Laboratory Medicine, University of Florida, Gainesville, FL
| | - Jeffrey B Jones
- Department of Plant Pathology, IFAS, University of Florida, Gainesville, FL
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13
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Wang H, Wagnon R, Moreno D, Timilsina S, Jones J, Vallad G, Turechek WW. A Long-Amplicon Viability-qPCR Test for Quantifying Living Pathogens that Cause Bacterial Spot in Tomato Seed. PLANT DISEASE 2022; 106:1474-1485. [PMID: 34894749 DOI: 10.1094/pdis-11-21-2509-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: 06/14/2023]
Abstract
Bacterial spot is one of the most serious diseases of tomato. It is caused by four species of Xanthomonas: X. euvesicatoria, X. gardneri, X. perforans, and X. vesicatoria. Contaminated or infected seed can be a major source of inoculum for this disease. The use of certified pathogen-free seed is one of the primary management practices to reduce the inoculum load in commercial production. Current seed testing protocols rely mainly on plating the seed extract and conventional PCR; however, the plating method cannot detect viable but nonculturable cells, and the conventional PCR assay has limited capability to differentiate DNA extracted from viable or dead bacterial cells. To improve the sensitivity and specificity of the tomato seed testing method for bacterial spot pathogens, a long-amplicon quantitative PCR (qPCR) assay coupled with propidium monoazide (PMA-qPCR) was developed to quantify selectively the four pathogenic Xanthomonas species in tomato seed. The optimized PMA-qPCR procedure was evaluated on pure bacterial suspensions, bacteria-spiked seed extracts, and seed extracts of inoculated and naturally infected seed. A crude DNA extraction protocol also was developed, and PMA-qPCR with crude bacterial DNA extracts resulted in accurate quantification of 104 to 108 CFU/ml of viable bacteria when mixed with dead cells at concentrations as high as 107 CFU/ml in the seed extracts. With DNA purified from concentrated seed extracts, the PMA-qPCR assay was able to detect DNA of the target pathogens in seed samples spiked with ≥75 CFU/ml (about 0.5 CFU/seed) of the viable pathogens. Latent class analysis of the inoculated and naturally infected seed samples showed that the PMA-qPCR assay had greater sensitivity than plating the seed extracts on the semiselective modified Tween Medium B and CKTM media for all four target species. Being much faster and more sensitive than dilution plating, the PMA-qPCR assay has potential to be used as a standalone tool or in combination with the plating method to improve tomato seed testing and advance the production of clean seed.
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Affiliation(s)
- Hehe Wang
- EDISTO Research and Education Center, Clemson University, Blackville, SC 29817
| | - Rieanna Wagnon
- EDISTO Research and Education Center, Clemson University, Blackville, SC 29817
| | - Daniela Moreno
- EDISTO Research and Education Center, Clemson University, Blackville, SC 29817
| | | | | | - Gary Vallad
- Gulf Coast Research and Education Center, University of Florida, Wimauma, FL 33598
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14
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Jibrin MO, Timilsina S, Minsavage GV, Vallad GE, Roberts PD, Goss EM, Jones JB. Bacterial Spot of Tomato and Pepper in Africa: Diversity, Emergence of T5 Race, and Management. Front Microbiol 2022; 13:835647. [PMID: 35509307 PMCID: PMC9058171 DOI: 10.3389/fmicb.2022.835647] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Accepted: 01/21/2022] [Indexed: 11/13/2022] Open
Abstract
Bacterial spot disease was first reported from South Africa by Ethel M. Doidge in 1920. In the ensuing century after the initial discovery, the pathogen has gained global attention in plant pathology research, providing insights into host-pathogen interactions, pathogen evolution, and effector discovery, such as the first discovery of transcription activation-like effectors, among many others. Four distinct genetic groups, including Xanthomonas euvesicatoria (proposed name: X. euvesicatoria pv. euvesicatoria), Xanthomonas perforans (proposed name: X. euvesicatoria pv. perforans), Xanthomonas gardneri (proposed name: Xanthomonas hortorum pv. gardneri), and Xanthomonas vesicatoria, are known to cause bacterial spot disease. Recently, a new race of a bacterial spot pathogen, race T5, which is a product of recombination between at least two Xanthomonas species, was reported in Nigeria. In this review, our focus is on the progress made on the African continent, vis-à-vis progress made in the global bacterial spot research community to provide a body of information useful for researchers in understanding the diversity, evolutionary changes, and management of the disease in Africa.
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Affiliation(s)
- Mustafa Ojonuba Jibrin
- Tree Fruit Research and Extension Center, Washington State University, Wenatchee, WA, United States
- Department of Crop Protection, Ahmadu Bello University, Zaria, Nigeria
| | - Sujan Timilsina
- Plant Pathology Department, University of Florida, Gainesville, FL, United States
| | - Gerald V. Minsavage
- Plant Pathology Department, University of Florida, Gainesville, FL, United States
| | - Garry E. Vallad
- Plant Pathology Department, University of Florida, Gainesville, FL, United States
- Gulf Coast Research and Education Center, University of Florida, Wimauma, FL, United States
| | - Pamela D. Roberts
- Plant Pathology Department, University of Florida, Gainesville, FL, United States
- UF/IFAS Southwest Florida Research and Education Center, Immokalee, FL, United States
| | - Erica M. Goss
- Plant Pathology Department, University of Florida, Gainesville, FL, United States
- Emerging Pathogens Institute, University of Florida, Gainesville, FL, United States
| | - Jeffrey B. Jones
- Plant Pathology Department, University of Florida, Gainesville, FL, United States
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15
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Bernal E, Rotondo F, Roman-Reyna V, Klass T, Timilsina S, Minsavage GV, Iruegas-Bocardo F, Goss EM, Jones JB, Jacobs JM, Miller SA, Francis DM. Migration Drives the Replacement of Xanthomonas perforans Races in the Absence of Widely Deployed Resistance. Front Microbiol 2022; 13:826386. [PMID: 35369455 PMCID: PMC8971904 DOI: 10.3389/fmicb.2022.826386] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 02/09/2022] [Indexed: 11/13/2022] Open
Abstract
Changes in Xanthomonas race and species composition causing bacterial spot of tomato have occurred throughout the world and are often associated with epidemics. Knowledge of bacterial population structure is key for resistance discovery and deployment. We surveyed Xanthomonas spp. composition from processing tomato fields in the Midwestern United States over a 4-year period between 2017 and 2020, compared these to strains collected previously, and found that X. perforans is currently the most prevalent species. We characterized 564 X. perforans isolates for sequence variation in avrXv3 to distinguish between race T3 and T4 and validated race designation using hypersensitive response (HR) assays for 106 isolates. Race T4 accounted for over 95% of X. perforans isolates collected in the Midwest between 2017 and 2020. Whole genome sequencing, Average Nucleotide Identity (ANI) analysis, core genome alignment and single nucleotide polymorphism (SNP) detection relative to a reference strain, and phylogenomic analysis suggest that the majority of Midwestern X. perforans strains collected between 2017 and 2020 were nearly identical, with greater than 99.99% ANI to X. perforans isolates collected from Collier County, Florida in 2012. These isolates shared a common SNP variant resulting an a premature stop codon in avrXv3. One sequenced isolate was identified with a deletion of avrXv3 and shared 99.99% ANI with a strain collected in Collier Co., Florida in 2006. A population shift to X. perforans T4 occurred in the absence of widely deployed resistance, with only 7% of tomato varieties tested having the resistant allele at the Xv3/Rx-4 locus. The persistence of nearly identical strains over multiple years suggests that migration led to the establishment of an endemic population. Our findings validate a genomics-based framework to track shifts in X. perforans populations due to migration, mutation, drift, or selection based on comparisons to 146 genomes.
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Affiliation(s)
- Eduardo Bernal
- Department of Horticulture and Crop Science, College of Food, Agricultural, and Environmental Sciences, The Ohio State University, Wooster, OH, United States
| | - Francesca Rotondo
- Department of Plant Pathology, College of Food, Agricultural, and Environmental Sciences, The Ohio State University, Wooster, OH, United States
| | - Veronica Roman-Reyna
- Department of Plant Pathology, College of Food, Agricultural, and Environmental Sciences, The Ohio State University, Columbus, OH, United States
- Infectious Diseases Institute, The Ohio State University, Columbus, OH, United States
| | - Taylor Klass
- Department of Plant Pathology, College of Food, Agricultural, and Environmental Sciences, The Ohio State University, Columbus, OH, United States
- Infectious Diseases Institute, The Ohio State University, Columbus, OH, United States
| | - Sujan Timilsina
- Department of Plant Pathology, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL, United States
| | - Gerald V. Minsavage
- Department of Plant Pathology, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL, United States
| | - Fernanda Iruegas-Bocardo
- Department of Plant Pathology, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL, United States
| | - Erica M. Goss
- Department of Plant Pathology, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL, United States
- Emerging Pathogens Institute, University of Florida, Gainesville, FL, United States
| | - Jeffrey B. Jones
- Department of Plant Pathology, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL, United States
| | - Jonathan M. Jacobs
- Department of Plant Pathology, College of Food, Agricultural, and Environmental Sciences, The Ohio State University, Columbus, OH, United States
- Infectious Diseases Institute, The Ohio State University, Columbus, OH, United States
| | - Sally A. Miller
- Department of Plant Pathology, College of Food, Agricultural, and Environmental Sciences, The Ohio State University, Wooster, OH, United States
| | - David M. Francis
- Department of Horticulture and Crop Science, College of Food, Agricultural, and Environmental Sciences, The Ohio State University, Wooster, OH, United States
- *Correspondence: David M. Francis,
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16
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Klein-Gordon JM, Timilsina S, Xing Y, Abrahamian P, Garrett KA, Jones JB, Vallad GE, Goss EM. Whole genome sequences reveal the Xanthomonas perforans population is shaped by the tomato production system. THE ISME JOURNAL 2022; 16:591-601. [PMID: 34489540 PMCID: PMC8776747 DOI: 10.1038/s41396-021-01104-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Revised: 08/11/2021] [Accepted: 08/23/2021] [Indexed: 02/08/2023]
Abstract
Modern agricultural practices increase the potential for plant pathogen spread, while the advent of affordable whole genome sequencing enables in-depth studies of pathogen movement. Population genomic studies may decipher pathogen movement and population structure as a result of complex agricultural production systems. We used whole genome sequences of 281 Xanthomonas perforans strains collected within one tomato production season across Florida and southern Georgia fields to test for population genetic structure associated with tomato production system variables. We identified six clusters of X. perforans from core gene SNPs that corresponded with phylogenetic lineages. Using whole genome SNPs, we found genetic structure among farms, transplant facilities, cultivars, seed producers, grower operations, regions, and counties. Overall, grower operations that produced their own transplants were associated with genetically distinct and less diverse populations of strains compared to grower operations that received transplants from multiple sources. The degree of genetic differentiation among components of Florida's tomato production system varied between clusters, suggesting differential dispersal of the strains, such as through seed or contaminated transplants versus local movement within farms. Overall, we showed that the genetic variation of a bacterial plant pathogen is shaped by the structure of the plant production system.
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Affiliation(s)
- Jeannie M Klein-Gordon
- Department of Plant Pathology, IFAS, University of Florida, Gainesville, FL, USA
- Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
| | - Sujan Timilsina
- Department of Plant Pathology, IFAS, University of Florida, Gainesville, FL, USA
| | - Yanru Xing
- Department of Plant Pathology, IFAS, University of Florida, Gainesville, FL, USA
- Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
- Food Systems Institute, University of Florida, Gainesville, FL, USA
| | - Peter Abrahamian
- Department of Plant Pathology, IFAS, University of Florida, Gainesville, FL, USA
- Gulf Coast Research and Education Center, IFAS, University of Florida, Balm, FL, USA
- USDA-ARS, Beltsville Agricultural Research Center, Molecular Plant Pathology Laboratory, Beltsville, MD, USA
| | - Karen A Garrett
- Department of Plant Pathology, IFAS, University of Florida, Gainesville, FL, USA
- Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
- Food Systems Institute, University of Florida, Gainesville, FL, USA
| | - Jeffrey B Jones
- Department of Plant Pathology, IFAS, University of Florida, Gainesville, FL, USA
| | - Gary E Vallad
- Department of Plant Pathology, IFAS, University of Florida, Gainesville, FL, USA.
- Gulf Coast Research and Education Center, IFAS, University of Florida, Balm, FL, USA.
| | - Erica M Goss
- Department of Plant Pathology, IFAS, University of Florida, Gainesville, FL, USA.
- Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA.
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17
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Osdaghi E, Jones JB, Sharma A, Goss EM, Abrahamian P, Newberry EA, Potnis N, Carvalho R, Choudhary M, Paret ML, Timilsina S, Vallad GE. A centenary for bacterial spot of tomato and pepper. MOLECULAR PLANT PATHOLOGY 2021; 22:1500-1519. [PMID: 34472193 PMCID: PMC8578828 DOI: 10.1111/mpp.13125] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 08/03/2021] [Accepted: 08/05/2021] [Indexed: 05/08/2023]
Abstract
DISEASE SYMPTOMS Symptoms include water-soaked areas surrounded by chlorosis turning into necrotic spots on all aerial parts of plants. On tomato fruits, small, water-soaked, or slightly raised pale-green spots with greenish-white halos are formed, ultimately becoming dark brown and slightly sunken with a scabby or wart-like surface. HOST RANGE Main and economically important hosts include different types of tomatoes and peppers. Alternative solanaceous and nonsolanaceous hosts include Datura spp., Hyoscyamus spp., Lycium spp., Nicotiana rustica, Physalis spp., Solanum spp., Amaranthus lividus, Emilia fosbergii, Euphorbia heterophylla, Nicandra physaloides, Physalis pubescens, Sida glomerata, and Solanum americanum. TAXONOMIC STATUS OF THE PATHOGEN Domain, Bacteria; phylum, Proteobacteria; class, Gammaproteobacteria; order, Xanthomonadales; family, Xanthomonadaceae; genus, Xanthomonas; species, X. euvesicatoria, X. hortorum, X. vesicatoria. SYNONYMS (NONPREFERRED SCIENTIFIC NAMES) Bacterium exitiosum, Bacterium vesicatorium, Phytomonas exitiosa, Phytomonas vesicatoria, Pseudomonas exitiosa, Pseudomonas gardneri, Pseudomonas vesicatoria, Xanthomonas axonopodis pv. vesicatoria, Xanthomonas campestris pv. vesicatoria, Xanthomonas cynarae pv. gardneri, Xanthomonas gardneri, Xanthomonas perforans. MICROBIOLOGICAL PROPERTIES Colonies are gram-negative, oxidase-negative, and catalase-positive and have oxidative metabolism. Pale-yellow domed circular colonies of 1-2 mm in diameter grow on general culture media. DISTRIBUTION The bacteria are widespread in Africa, Brazil, Canada and the USA, Australia, eastern Europe, and south-east Asia. Occurrence in western Europe is restricted. PHYTOSANITARY CATEGORIZATION A2 no. 157, EU Annex designation II/A2. EPPO CODES XANTEU, XANTGA, XANTPF, XANTVE.
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Affiliation(s)
- Ebrahim Osdaghi
- Department of Plant ProtectionCollege of AgricultureUniversity of TehranKarajIran
| | - Jeffrey B. Jones
- Plant Pathology DepartmentUniversity of FloridaGainesvilleFloridaUSA
| | - Anuj Sharma
- Plant Pathology DepartmentUniversity of FloridaGainesvilleFloridaUSA
| | - Erica M. Goss
- Plant Pathology DepartmentUniversity of FloridaGainesvilleFloridaUSA
- Emerging Pathogens InstituteUniversity of FloridaGainesvilleFloridaUSA
| | - Peter Abrahamian
- Plant Pathology DepartmentUniversity of FloridaGainesvilleFloridaUSA
- Gulf Coast Research and Education CenterUniversity of FloridaWimaumaFloridaUSA
| | - Eric A. Newberry
- Department of Entomology and Plant PathologyAuburn UniversityAuburnAlabamaUSA
| | - Neha Potnis
- Department of Entomology and Plant PathologyAuburn UniversityAuburnAlabamaUSA
| | - Renato Carvalho
- Plant Pathology DepartmentUniversity of FloridaGainesvilleFloridaUSA
| | - Manoj Choudhary
- Plant Pathology DepartmentUniversity of FloridaGainesvilleFloridaUSA
| | - Mathews L. Paret
- Department of Plant PathologyNorth Florida Research and Education CenterUniversity of FloridaQuincyFloridaUSA
| | - Sujan Timilsina
- Plant Pathology DepartmentUniversity of FloridaGainesvilleFloridaUSA
| | - Gary E. Vallad
- Gulf Coast Research and Education CenterUniversity of FloridaWimaumaFloridaUSA
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18
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Sharma A, Timilsina S, Abrahamian P, Minsavage GV, Colee J, Ojiambo PS, Goss EM, Vallad GE, Jones JB. Need for speed: bacterial effector XopJ2 is associated with increased dispersal velocity of Xanthomonas perforans. Environ Microbiol 2021; 23:5850-5865. [PMID: 33891376 PMCID: PMC8597037 DOI: 10.1111/1462-2920.15541] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Accepted: 04/20/2021] [Indexed: 11/28/2022]
Abstract
Bacterial spot caused by Xanthomonas perforans (Xp) is an economically important disease in tomato. Previous studies have shown that the recently isolated Xp strains have acquired and retained the effector gene, xopJ2, which has been reported to increase fitness of the pathogen in the field. To elucidate the fitness benefit of xopJ2, we quantified the effect of xopJ2 on the dispersal and evolution of Xp populations on tomato. We compared movement of two wild-type Xp strains expressing xopJ2 to their respective xopJ2 mutants when co-inoculated in the field. We developed a binary logistic model to predict the presence of Xp over spatial and temporal dimensions with or without xopJ2. Based on the model, wild-type bacteria were dispersed approximately three times faster than the xopJ2 mutants. In a simulation experiment, the selective advantage due to increased dispersal velocity led to an increase in the frequency of xopJ2 gene in the Xp population and its apparent fixation within 10 to 12 cropping seasons of the tomato crop. Our results show that the presence of a single gene can affect the dispersal of a bacterial pathogen and significantly alter its population dynamics.
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Affiliation(s)
- Anuj Sharma
- Department of Plant PathologyUniversity of FloridaGainesvilleFloridaUSA
| | - Sujan Timilsina
- Department of Plant PathologyUniversity of FloridaGainesvilleFloridaUSA
| | - Peter Abrahamian
- Gulf Coast Research and Education CenterUniversity of FloridaWimaumaFloridaUSA
| | | | - James Colee
- Statistics Consulting Unit, Institute of Food and Agricultural SciencesUniversity of FloridaGainesvilleFloridaUSA
| | - Peter S. Ojiambo
- Department of Entomology and Plant PathologyNorth Carolina State UniversityRaleighNorth CarolinaUSA
| | - Erica M. Goss
- Department of Plant PathologyUniversity of FloridaGainesvilleFloridaUSA
- Emerging Pathogens InstituteUniversity of FloridaGainesvilleFloridaUSA
| | - Gary E. Vallad
- Gulf Coast Research and Education CenterUniversity of FloridaWimaumaFloridaUSA
| | - Jeffrey B. Jones
- Department of Plant PathologyUniversity of FloridaGainesvilleFloridaUSA
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19
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Huang CJ, Wu TL, Zheng PX, Ou JY, Ni HF, Lin YC. Comparative Genomic Analysis Uncovered Evolution of Pathogenicity Factors, Horizontal Gene Transfer Events, and Heavy Metal Resistance Traits in Citrus Canker Bacterium Xanthomonas citri subsp. citri. Front Microbiol 2021; 12:731711. [PMID: 34557177 PMCID: PMC8453159 DOI: 10.3389/fmicb.2021.731711] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 08/18/2021] [Indexed: 12/30/2022] Open
Abstract
Background: Worldwide citrus production is severely threatened by Asiatic citrus canker which is caused by the proteobacterium Xanthomonas citri subsp. citri. Foliar sprays of copper-based bactericides are frequently used to control plant bacterial diseases. Despite the sequencing of many X. citri strains, the genome diversity and distribution of genes responsible for metal resistance in X. citri subsp. citri strains from orchards with different management practices in Taiwan are not well understood. Results: The genomes of three X. citri subsp. citri strains including one copper-resistant strain collected from farms with different management regimes in Taiwan were sequenced by Illumina and Nanopore sequencing and assembled into complete circular chromosomes and plasmids. CRISPR spoligotyping and phylogenomic analysis indicated that the three strains were located in the same phylogenetic lineages and shared ∼3,000 core-genes with published X. citri subsp. citri strains. These strains differed mainly in the CRISPR repeats and pathogenicity-related plasmid-borne transcription activator-like effector (TALE)-encoding pthA genes. The copper-resistant strain has a unique, large copper resistance plasmid due to an unusual ∼40 kbp inverted repeat. Each repeat contains a complete set of the gene cluster responsible for copper and heavy metal resistance. Conversely, the copper sensitive strains carry no metal resistance genes in the plasmid. Through comparative analysis, the origin and evolution of the metal resistance clusters was resolved. Conclusion: Chromosomes remained constant among three strains collected in Taiwan, but plasmids likely played an important role in maintaining pathogenicity and developing bacterial fitness in the field. The evolution of pathogenicity factors and horizontal gene transfer events were observed in the three strains. These data suggest that agricultural management practices could be a potential trigger for the evolution of citrus canker pathogens. The decrease in the number of CRISPR repeats and pthA genes might be the result of adaptation to a less stressful environment. The metal resistance genes in the copper resistant X. citri strain likely originated from the Mauritian strain not the local copper-resistant X. euvesicatoria strain. This study highlights the importance of plasmids as 'vehicles' for exchanging genetic elements between plant pathogenic bacteria and contributing to bacterial adaptation to the environment.
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Affiliation(s)
- Chien-Jui Huang
- Department of Plant Medicine, National Chiayi University, Chiayi, Taiwan
| | - Ting-Li Wu
- Biotechnology Center in Southern Taiwan, Agricultural Biotechnology Research Center, Academia Sinica, Tainan, Taiwan
| | - Po-Xing Zheng
- Biotechnology Center in Southern Taiwan, Agricultural Biotechnology Research Center, Academia Sinica, Tainan, Taiwan
| | - Jheng-Yang Ou
- Biotechnology Center in Southern Taiwan, Agricultural Biotechnology Research Center, Academia Sinica, Tainan, Taiwan
| | - Hui-Fang Ni
- Department of Plant Protection, Chiayi Agricultural Experiment Station, Taiwan Agricultural Research Institute, Chiayi, Taiwan
| | - Yao-Cheng Lin
- Biotechnology Center in Southern Taiwan, Agricultural Biotechnology Research Center, Academia Sinica, Tainan, Taiwan
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20
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Potnis N. Harnessing Eco-Evolutionary Dynamics of Xanthomonads on Tomato and Pepper to Tackle New Problems of an Old Disease. ANNUAL REVIEW OF PHYTOPATHOLOGY 2021; 59:289-310. [PMID: 34030449 DOI: 10.1146/annurev-phyto-020620-101612] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Bacterial spot is an endemic seedborne disease responsible for recurring outbreaks on tomato and pepper around the world. The disease is caused by four diverse species, Xanthomonas gardneri, Xanthomonas euvesicatoria, Xanthomonas perforans, and Xanthomonas vesicatoria. There are no commercially available disease-resistant tomato varieties, and the disease is managed by chemical/biological control options, although these have not reduced the incidence of outbreaks. The disease on peppers is managed by disease-resistant cultivars that are effective against X. euvesicatoria but not X. gardneri. A significant shift in composition and prevalence of different species and races of the pathogen has occurred over the past century. Here, I attempt to review ecological and evolutionary processes associated with the population dynamics leading to disease emergence and spread. The goal of this review is to integrate the knowledge on population genomics and molecular plant-microbe interactions for this pathosystem to tailor disease management strategies.
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Affiliation(s)
- Neha Potnis
- Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama 36849, USA;
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21
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Abrahamian P, Klein-Gordon JM, Jones JB, Vallad GE. Epidemiology, diversity, and management of bacterial spot of tomato caused by Xanthomonas perforans. Appl Microbiol Biotechnol 2021; 105:6143-6158. [PMID: 34342710 DOI: 10.1007/s00253-021-11459-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Revised: 07/05/2021] [Accepted: 07/09/2021] [Indexed: 11/28/2022]
Abstract
Tomato is an important crop grown worldwide. Various plant diseases cause massive losses in tomato plants due to diverse biotic agents. Bacterial spot of tomato (BST) is a worldwide disease that results in high losses in processed and fresh tomato. Xanthomonas perforans, an aerobic, single-flagellated, rod-shaped, Gram-negative plant pathogenic bacterium, is one of the leading causes of BST. Over the past three decades, X. perforans has increasingly been reported from tomato-growing regions and became a major bacterial disease. X. perforans thrives under high humidity and high temperature, which is commonplace in tropical and subtropical climates. Distinguishing symptoms of BST are necrotic lesions that can coalesce and cause a shot-hole appearance. X. perforans can occasionally cause fruit symptoms depending on disease pressure during fruit development. Short-distance movement in the field is mainly dependent on wind-driven rain, whereas long distance movement occurs through contaminated seed or plant material. X. perforans harbors a suite of effectors that increase pathogen virulence, fitness, and dissemination. BST management mainly relies on copper-based compounds; however, resistance is widespread. Alternative compounds, such as nanomaterials, are currently being evaluated and show high potential for BST management. Resistance breeding remains difficult to attain due to limited resistant germplasm. While the increased genetic diversity and gain and loss of effectors in X. perforans limits the success of single-gene resistance, the adoption of effector-specific transgenes and quantitative resistance may lead to durable host resistance. However, further research that aims to more effectively implement novel management tools is required to curb disease spread. KEY POINTS: • Xanthomonas perforans causes bacterial spot on tomato epidemics through infected seedlings and movement of plant material. • Genetic diversity plays a major role in shaping populations which is evident in loss and gain of effectors. • Management relies on copper sprays, but nanoparticles are a promising alternative to reduce copper toxicity.
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Affiliation(s)
- Peter Abrahamian
- Beltsville Agricultural Research Center, Molecular Plant Pathology Laboratory, USDA-ARS, Beltsville, MD, 20705, USA.
| | | | - Jeffrey B Jones
- Department of Plant Pathology, University of Florida, Gainesville, FL, 32611, USA
| | - Gary E Vallad
- Gulf Coast Research and Education Center, University of Florida, Wimauma, FL, 33598, USA.
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Vinatzer BA. The Power of a Statewide Survey When Phenotypic Testing Is Combined with Genomics-Enabled Molecular Characterization and Network Analyses. PHYTOPATHOLOGY 2021; 111:904-905. [PMID: 34281354 DOI: 10.1094/phyto-01-21-0025-ia] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Affiliation(s)
- Boris A Vinatzer
- School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, VA
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23
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Klein-Gordon JM, Xing Y, Garrett KA, Abrahamian P, Paret ML, Minsavage GV, Strayer-Scherer AL, Fulton JC, Timilsina S, Jones JB, Goss EM, Vallad GE. Assessing Changes and Associations in the Xanthomonas perforans Population Across Florida Commercial Tomato Fields Via a Statewide Survey. PHYTOPATHOLOGY 2021; 111:1029-1041. [PMID: 33048630 DOI: 10.1094/phyto-09-20-0402-r] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Before 1991, Xanthomonas euvesicatoria was the causal agent of bacterial spot of tomato in Florida but was quickly replaced by X. perforans. The X. perforans population has changed in genotype and phenotype despite lack of a clear selection pressure. To determine the current Xanthomonas population in Florida, we collected 585 Xanthomonas strains from 70 tomato fields, representing 22 farms across eight counties, in the Florida tomato production region. Strains were isolated from 23 cultivars across eight seed producers and were associated with eight transplant facilities during the fall 2017 season. Our collection was phenotypically and genotypically characterized. Only X. perforans was identified, and all strains except one (99.8%) were tolerant to copper sulfate and 25% of strains were resistant to streptomycin sulfate. Most of the strains (99.3%) that were resistant to streptomycin sulfate were sequence type 1. The X. perforans population consisted of tomato races 3 (8%) and 4 (92%) and all three previously reported sequence types, ranging from 22 to 46% frequency. Approximately half of all strains, none of which were sequence type 2, produced bacteriocins against X. euvesicatoria. Effector profiles were highly variable among strains, which could impact the strains' host range. The effector xopJ4, which was previously thought to be conserved in X. perforans tomato pathogens, was absent in 19 strains. Nonmetric multidimensional scaling and network analyses show how strains and strain traits were associated with production system variables, including anonymized farms and transplant facilities. These analyses show that the composition of the Florida X. perforans population is diverse and complex.
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Affiliation(s)
- Jeannie M Klein-Gordon
- Department of Plant Pathology, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611
- Emerging Pathogens Institute, University of Florida, Gainesville, FL 32611
| | - Yanru Xing
- Department of Plant Pathology, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611
- Emerging Pathogens Institute, University of Florida, Gainesville, FL 32611
- Food Systems Institute, University of Florida, Gainesville, FL 32611
| | - Karen A Garrett
- Department of Plant Pathology, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611
- Emerging Pathogens Institute, University of Florida, Gainesville, FL 32611
- Food Systems Institute, University of Florida, Gainesville, FL 32611
| | - Peter Abrahamian
- Department of Plant Pathology, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611
- Gulf Coast Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Balm, FL 33598
| | - Matthews L Paret
- Department of Plant Pathology, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611
- North Florida Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Quincy, FL 32351
| | - Gerald V Minsavage
- Department of Plant Pathology, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611
| | | | - James C Fulton
- Department of Plant Pathology, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611
| | - Sujan Timilsina
- Department of Plant Pathology, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611
| | - Jeffrey B Jones
- Department of Plant Pathology, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611
| | - Erica M Goss
- Department of Plant Pathology, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611
- Emerging Pathogens Institute, University of Florida, Gainesville, FL 32611
| | - Gary E Vallad
- Department of Plant Pathology, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611
- Gulf Coast Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Balm, FL 33598
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24
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Catara V, Cubero J, Pothier JF, Bosis E, Bragard C, Đermić E, Holeva MC, Jacques MA, Petter F, Pruvost O, Robène I, Studholme DJ, Tavares F, Vicente JG, Koebnik R, Costa J. Trends in Molecular Diagnosis and Diversity Studies for Phytosanitary Regulated Xanthomonas. Microorganisms 2021; 9:862. [PMID: 33923763 PMCID: PMC8073235 DOI: 10.3390/microorganisms9040862] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 04/10/2021] [Accepted: 04/12/2021] [Indexed: 11/17/2022] Open
Abstract
Bacteria in the genus Xanthomonas infect a wide range of crops and wild plants, with most species responsible for plant diseases that have a global economic and environmental impact on the seed, plant, and food trade. Infections by Xanthomonas spp. cause a wide variety of non-specific symptoms, making their identification difficult. The coexistence of phylogenetically close strains, but drastically different in their phenotype, poses an added challenge to diagnosis. Data on future climate change scenarios predict an increase in the severity of epidemics and a geographical expansion of pathogens, increasing pressure on plant health services. In this context, the effectiveness of integrated disease management strategies strongly depends on the availability of rapid, sensitive, and specific diagnostic methods. The accumulation of genomic information in recent years has facilitated the identification of new DNA markers, a cornerstone for the development of more sensitive and specific methods. Nevertheless, the challenges that the taxonomic complexity of this genus represents in terms of diagnosis together with the fact that within the same bacterial species, groups of strains may interact with distinct host species demonstrate that there is still a long way to go. In this review, we describe and discuss the current molecular-based methods for the diagnosis and detection of regulated Xanthomonas, taxonomic and diversity studies in Xanthomonas and genomic approaches for molecular diagnosis.
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Affiliation(s)
- Vittoria Catara
- Department of Agriculture, Food and Environment, University of Catania, 95125 Catania, Italy
| | - Jaime Cubero
- National Institute for Agricultural and Food Research and Technology (INIA), 28002 Madrid, Spain;
| | - Joël F. Pothier
- Environmental Genomics and Systems Biology Research Group, Institute for Natural Resource Sciences, Zurich University of Applied Sciences (ZHAW), 8820 Wädenswil, Switzerland;
| | - Eran Bosis
- Department of Biotechnology Engineering, ORT Braude College of Engineering, Karmiel 2161002, Israel;
| | - Claude Bragard
- UCLouvain, Earth & Life Institute, Applied Microbiology, 1348 Louvain-la-Neuve, Belgium;
| | - Edyta Đermić
- Department of Plant Pathology, Faculty of Agriculture, University of Zagreb, 10000 Zagreb, Croatia;
| | - Maria C. Holeva
- Benaki Phytopathological Institute, Scientific Directorate of Phytopathology, Laboratory of Bacteriology, GR-14561 Kifissia, Greece;
| | - Marie-Agnès Jacques
- IRHS, INRA, AGROCAMPUS-Ouest, Univ Angers, SFR 4207 QUASAV, 49071 Beaucouzé, France;
| | - Francoise Petter
- European and Mediterranean Plant Protection Organization (EPPO/OEPP), 75011 Paris, France;
| | - Olivier Pruvost
- CIRAD, UMR PVBMT, F-97410 Saint Pierre, La Réunion, France; (O.P.); (I.R.)
| | - Isabelle Robène
- CIRAD, UMR PVBMT, F-97410 Saint Pierre, La Réunion, France; (O.P.); (I.R.)
| | | | - Fernando Tavares
- CIBIO—Centro de Investigação em Biodiversidade e Recursos Genéticos, InBIO-Laboratório Associado, Universidade do Porto, 4485-661 Vairão, Portugal; or
- FCUP-Faculdade de Ciências, Departamento de Biologia, Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal
| | | | - Ralf Koebnik
- Plant Health Institute of Montpellier (PHIM), Univ Montpellier, Cirad, INRAe, Institut Agro, IRD, 34398 Montpellier, France;
| | - Joana Costa
- Centre for Functional Ecology-Science for People & the Planet, Department of Life Sciences, University of Coimbra, 300-456 Coimbra, Portugal
- Laboratory for Phytopathology, Instituto Pedro Nunes, 3030-199 Coimbra, Portugal
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25
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Draft Genome Sequences of Pseudomonas syringae pv. tomato Strains J4 and J6, Isolated in Florida. Microbiol Resour Announc 2021; 10:10/15/e00127-21. [PMID: 33858923 PMCID: PMC8050965 DOI: 10.1128/mra.00127-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas syringae pv. Tomato causes bacterial speck in tomato. We report the genome sequences of two P. syringae pv. Tomato strains, J4 and J6, that are genetically closely related, with >99.9 average nucleotide identity (ANI), but vary in the presence of coronatine-associated genes. Pseudomonas syringae pv. tomato causes bacterial speck in tomato. We report the genome sequences of two P. syringae pv. tomato strains, J4 and J6, that are genetically closely related, with >99.9 average nucleotide identity (ANI), but vary in the presence of coronatine-associated genes.
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26
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Vancheva T, Bogatzevska N, Moncheva P, Mitrev S, Vernière C, Koebnik R. Molecular Epidemiology of Xanthomonas euvesicatoria Strains from the Balkan Peninsula Revealed by a New Multiple-Locus Variable-Number Tandem-Repeat Analysis Scheme. Microorganisms 2021; 9:microorganisms9030536. [PMID: 33807692 PMCID: PMC8002079 DOI: 10.3390/microorganisms9030536] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 02/25/2021] [Accepted: 03/01/2021] [Indexed: 11/24/2022] Open
Abstract
Bacterial spot of pepper and tomato is caused by at least three species of Xanthomonas, among them two pathovars of Xanthomonas euvesicatoria, which are responsible for significant yield losses on all continents. In order to trace back the spread of bacterial spot pathogens within and among countries, we developed the first multilocus variable number of tandem repeat analyses (MLVA) scheme for pepper- and tomato-pathogenic strains of X. euvesicatoria. In this work, we assessed the repeat numbers by DNA sequencing of 16 tandem repeat loci and applied this new tool to analyse a representative set of 88 X. euvesicatoria pepper strains from Bulgaria and North Macedonia. The MLVA-16 scheme resulted in a Hunter–Gaston Discriminatory Index (HGDI) score of 0.944 and allowed to resolve 36 MLVA haplotypes (MTs), thus demonstrating its suitability for high-resolution molecular typing. Strains from the different regions of Bulgaria and North Macedonia were found to be widespread in genetically distant clonal complexes or singletons. Sequence types of the variable number of tandem repeats (VNTR) amplicons revealed cases of size homoplasy and suggested the coexistence of different populations and different introduction events. The large geographical distribution of MTs and the existence of epidemiologically closely related strains in different regions and countries suggest long dispersal of strains on pepper in this area.
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Affiliation(s)
- Taca Vancheva
- IPME, Univ Montpellier, Cirad, IRD, Montpellier, France;
- Department of General and Industrial Microbiology, Faculty of Biology, Sofia University ‘St. Kliment Ohridski’, Sofia, Bulgaria;
| | - Nevena Bogatzevska
- Institute of Soil Science, Agrotechnologies and Plant Protection ‘Nikola Pushkarov’, Sofia, Bulgaria;
| | - Penka Moncheva
- Department of General and Industrial Microbiology, Faculty of Biology, Sofia University ‘St. Kliment Ohridski’, Sofia, Bulgaria;
| | - Sasa Mitrev
- Department for Plant and Environment Protection, Faculty of Agriculture, Goce Delchev University, Štip, North Macedonia;
| | - Christian Vernière
- Plant Health Institute of Montpellier (PHIM), Univ Montpellier, Cirad, INRAe, Insitut Agro, IRD, Montpellier, France;
| | - Ralf Koebnik
- IPME, Univ Montpellier, Cirad, IRD, Montpellier, France;
- Plant Health Institute of Montpellier (PHIM), Univ Montpellier, Cirad, INRAe, Insitut Agro, IRD, Montpellier, France;
- Correspondence: ; Tel.: +33-467-416-228
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27
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Abrahamian P, Sharma A, Jones JB, Vallad GE. Dynamics and Spread of Bacterial Spot Epidemics in Tomato Transplants Grown for Field Production. PLANT DISEASE 2021; 105:566-575. [PMID: 32865478 DOI: 10.1094/pdis-05-20-0945-re] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Tomato transplants are the primary means of establishing commercial tomato production fields in the eastern United States. Transplants are often suspected as the source of inoculum for major outbreaks in production fields of bacterial spot of tomato (BST) caused by Xanthomonas perforans (Xp). A combination of high plant densities with overhead irrigation, high humidity, and high temperatures are conducive to BST outbreaks during transplant production. In addition to chemical control, transplant growers use roguing to remove diseased transplants, as a primary way to manage BST during transplant production. The value of roguing is often questioned, because information about the rate of pathogen spread and the incubation period between infection and symptom development is limited. In this study, we evaluated the extent of X. perforans spread on tomato transplants relative to symptom development by using a rifampicin-resistant X. perforans strain and conducting experiments in an environmentally controlled greenhouse simulating grower practices and also at a commercial transplant facility in Florida. BST symptom development typically lagged behind X. perforans dispersal by at least 5 to 7 days depending on environmental conditions. Furthermore, X. perforans was capable of aerosolization, which resulted in long-distance dispersal of ≤2 m under highly favorable conditions. Growers should rogue diseased plants and surrounding nonsymptomatic plants by >1 and ≤3 m, depending on outbreak severity, to limit disease spread. As a result, proper disease management should reduce introduction of nonsymptomatic transplants into the field and subsequently reduce pesticide applications.
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Affiliation(s)
| | - Anuj Sharma
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611
| | - Jeffrey B Jones
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611
| | - Gary E Vallad
- Gulf Coast Research and Education Center, Wimauma, FL 33598
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28
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Webster J, Bogema D, Chapman TA. Comparative Genomics of Xanthomonas citri pv. citri A* Pathotype Reveals Three Distinct Clades with Varying Plasmid Distribution. Microorganisms 2020; 8:microorganisms8121947. [PMID: 33302542 PMCID: PMC7764509 DOI: 10.3390/microorganisms8121947] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 12/04/2020] [Accepted: 12/07/2020] [Indexed: 11/23/2022] Open
Abstract
Citrus bacterial canker (CBC) is an important disease of citrus cultivars worldwide that causes blister-like lesions on host plants and leads to more severe symptoms such as plant defoliation and premature fruit drop. The causative agent, Xanthomonas citri pv. citri, exists as three pathotypes—A, A*, and Aw—which differ in their host range and elicited host response. To date, comparative analyses have been hampered by the lack of closed genomes for the A* pathotype. In this study, we sequenced and assembled six CBC isolates of pathotype A* using second- and third-generation sequencing technologies to produce complete, closed assemblies. Analysis of these genomes and reference A, A*, and Aw sequences revealed genetic groups within the A* pathotype. Investigation of accessory genomes revealed virulence factors, including type IV secretion systems and heavy metal resistance genes, differentiating the genetic groups. Genomic comparisons of closed genome assemblies also provided plasmid distribution information for the three genetic groups of A*. The genomes presented here complement existing closed genomes of A and Aw pathotypes that are publicly available and open opportunities to investigate the evolution of X. citri pv. citri and the virulence factors that contribute to this serious pathogen.
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29
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Goss EM, Kendig AE, Adhikari A, Lane B, Kortessis N, Holt RD, Clay K, Harmon PF, Flory SL. Disease in Invasive Plant Populations. ANNUAL REVIEW OF PHYTOPATHOLOGY 2020; 58:97-117. [PMID: 32516034 DOI: 10.1146/annurev-phyto-010820-012757] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Non-native invasive plants can establish in natural areas, where they can be ecologically damaging and costly to manage. Like cultivated plants, invasive plants can experience a relatively disease-free period upon introduction and accumulate pathogens over time. Diseases of invasive plant populations are infrequently studied compared to diseases of agriculture, forestry, and even native plant populations. We evaluated similarities and differences in the processes that are likely to affect pathogen accumulation and disease in invasive plants compared to cultivated plants, which are the dominant focus of the field of plant pathology. Invasive plants experience more genetic, biotic, and abiotic variation across space and over time than cultivated plants, which is expected to stabilize the ecological and evolutionary dynamics of interactions with pathogens and possibly weaken the efficacy of infectious disease in their control. Although disease is expected to be context dependent, the widespread distribution of invasive plants makes them important pathogen reservoirs. Research on invasive plant diseases can both protect crops and help manage invasive plant populations.
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Affiliation(s)
- Erica M Goss
- Department of Plant Pathology and Emerging Pathogens Institute, University of Florida, Gainesville, Florida 32611, USA;
| | - Amy E Kendig
- Agronomy Department, University of Florida, Gainesville, Florida 32611, USA
| | - Ashish Adhikari
- Department of Plant Pathology, University of Florida, Gainesville, Florida 32611, USA
| | - Brett Lane
- Department of Plant Pathology, University of Florida, Gainesville, Florida 32611, USA
| | - Nicholas Kortessis
- Department of Biology, University of Florida, Gainesville, Florida 32611, USA
| | - Robert D Holt
- Department of Biology, University of Florida, Gainesville, Florida 32611, USA
| | - Keith Clay
- Department of Ecology and Evolutionary Biology, Tulane University, New Orleans, Louisiana 70118, USA
| | - Philip F Harmon
- Department of Plant Pathology, University of Florida, Gainesville, Florida 32611, USA
| | - S Luke Flory
- Agronomy Department, University of Florida, Gainesville, Florida 32611, USA
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30
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Baltrus DA. Bacterial dispersal and biogeography as underappreciated influences on phytobiomes. CURRENT OPINION IN PLANT BIOLOGY 2020; 56:37-46. [PMID: 32278259 DOI: 10.1016/j.pbi.2020.02.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 02/14/2020] [Accepted: 02/25/2020] [Indexed: 06/11/2023]
Abstract
Bacterial strains are not distributed evenly throughout the environment. Here I explore how differential distribution and dispersal patterns of bacteria could affect interactions and coevolutionary dynamics with plants, and highlight ways that variation could be taken advantage of to develop robust and effective microbial consortia to inoculate crops. Questions about biogeographical patterns in viruses, fungi, and other eukaryotes are equally as prevalent and important for agriculture, and are in some cases more thoroughly explored. For simplicity as well as to bring attention to bacterial biogeography and dispersal in the context of plant interactions, I focus solely on bacterial patterns and questions for this article. The next few years will no doubt bring great advances in our understanding of dispersal capabilities and population dynamics for many plant-associated bacteria, and one of the next looming challenges will be learning to harvest this diversity in ways that can benefit agriculture.
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Affiliation(s)
- David A Baltrus
- School of Plant Sciences, University of Arizona, Tucson AZ, USA; School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson AZ, USA.
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31
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Timilsina S, Potnis N, Newberry EA, Liyanapathiranage P, Iruegas-Bocardo F, White FF, Goss EM, Jones JB. Xanthomonas diversity, virulence and plant-pathogen interactions. Nat Rev Microbiol 2020; 18:415-427. [PMID: 32346148 DOI: 10.1038/s41579-020-0361-8] [Citation(s) in RCA: 132] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/19/2020] [Indexed: 12/19/2022]
Abstract
Xanthomonas spp. encompass a wide range of plant pathogens that use numerous virulence factors for pathogenicity and fitness in plant hosts. In this Review, we examine recent insights into host-pathogen co-evolution, diversity in Xanthomonas populations and host specificity of Xanthomonas spp. that have substantially improved our fundamental understanding of pathogen biology. We emphasize the virulence factors in xanthomonads, such as type III secreted effectors including transcription activator-like effectors, type II secretion systems, diversity resulting in host specificity, evolution of emerging strains, activation of susceptibility genes and strategies of host evasion. We summarize the genomic diversity in several Xanthomonas spp. and implications for disease outbreaks, management strategies and breeding for disease resistance.
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Affiliation(s)
- Sujan Timilsina
- Plant Pathology Department, University of Florida, Gainesville, FL, USA
| | - Neha Potnis
- Entomology and Plant Pathology, Auburn University, Auburn, AL, USA
| | - Eric A Newberry
- Entomology and Plant Pathology, Auburn University, Auburn, AL, USA
| | | | | | - Frank F White
- Plant Pathology Department, University of Florida, Gainesville, FL, USA
| | - Erica M Goss
- Plant Pathology Department, University of Florida, Gainesville, FL, USA. .,Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA.
| | - Jeffrey B Jones
- Plant Pathology Department, University of Florida, Gainesville, FL, USA.
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32
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Newberry E, Bhandari R, Kemble J, Sikora E, Potnis N. Genome-resolved metagenomics to study co-occurrence patterns and intraspecific heterogeneity among plant pathogen metapopulations. Environ Microbiol 2020; 22:2693-2708. [PMID: 32207218 DOI: 10.1111/1462-2920.14989] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 03/09/2020] [Accepted: 03/18/2020] [Indexed: 01/12/2023]
Abstract
Assessment of pathogen diversity in agricultural fields is essential for informing management decisions and the development of resistant plant varieties. However, many population genomic studies have relied on culture-based approaches that do not provide quantitative assessment of pathogen populations at the field-level or the associated host microbiome. Here, we applied whole-genome shotgun sequencing of microbial DNA extracted directly from the washings of pooled leaf samples, collected from individual tomato and pepper fields in Alabama that displayed the classical symptoms of bacterial spot disease caused by Xanthomonas spp. Our results revealed that while the occurrence of both X. perforans and X. euvesicatoria within fields was limited, evidence of co-occurrence of up to three distinct X. perforans genotypes was obtained in 7 of 10 tomato fields sampled. These population dynamics were accompanied by the corresponding type 3 secreted effector repertoires associated with the co-occurring X. perforans genotypes, indicating that metapopulation structure within fields should be considered when assessing the adaptive potential of X. perforans. Finally, analysis of microbial community composition revealed that co-occurrence of the bacterial spot pathogens Pseudomonas cichorii and Xanthomonas spp. is common in Alabama fields and provided evidence for the non-random association of several other human and plant opportunists.
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Affiliation(s)
- Eric Newberry
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, USA
| | - Rishi Bhandari
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, USA
| | - Joseph Kemble
- Department of Horticulture, Auburn University, Auburn, AL, USA
| | - Edward Sikora
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, USA.,Alabama Cooperative Extension System, Auburn, AL, USA
| | - Neha Potnis
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, USA
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33
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Independent Evolution with the Gene Flux Originating from Multiple Xanthomonas Species Explains Genomic Heterogeneity in Xanthomonas perforans. Appl Environ Microbiol 2019; 85:AEM.00885-19. [PMID: 31375496 DOI: 10.1128/aem.00885-19] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 07/31/2019] [Indexed: 12/31/2022] Open
Abstract
Xanthomonas perforans is the predominant pathogen responsible for bacterial leaf spot of tomato and X. euvesicatoria for that of pepper in the southeast United States. Previous studies have indicated significant changes in the X. perforans population collected from Florida tomato fields over the span of 2 decades, including a shift in race and diversification into three phylogenetic groups driven by genome-wide homologous-recombination events derived from X. euvesicatoria In our sampling of Xanthomonas strains associated with bacterial spot disease in Alabama, we were readily able to isolate X. perforans from symptomatic pepper plants grown in several Alabama counties, indicating a recent shift in the host range of the pathogen. To investigate the diversity of these pepper-pathogenic strains and their relation to populations associated with tomatoes grown in the southeast United States, we sequenced the genomes of eight X. perforans strains isolated from tomatoes and peppers grown in Alabama and compared them with previously published genome data available from GenBank. Surprisingly, reconstruction of the X. perforans core genome revealed the presence of two novel genetic groups in Alabama that each harbored a different transcription activation-like effector (TALE). While one TALE, AvrHah1, was associated with an emergent lineage pathogenic to both tomato and pepper, the other was identified as a new class within the AvrBs3 family, here designated PthXp1, and was associated with enhanced symptom development on tomato. Examination of patterns of homologous recombination across the larger X. euvesicatoria species complex revealed a dynamic pattern of gene flow, with multiple donors of Xanthomonas spp. associated with diverse hosts of isolation.IMPORTANCE Bacterial leaf spot of tomato and pepper is an endemic plant disease with a global distribution. In this study, we investigated the evolutionary processes leading to the emergence of novel X. perforans lineages identified in Alabama. While one lineage was isolated from symptomatic tomato and pepper plants, confirming the host range expansion of X. perforans, the other lineage was isolated from tomato and acquired a novel transcription activation-like effector, here designated PthXp1. Functional analysis of PthXp1 indicated that it does not induce Bs4-mediated resistance in tomato and contributes to virulence, providing an adaptive advantage to strains on tomato. Our findings also show that different phylogenetic groups of the pathogen have experienced independent recombination events originating from multiple Xanthomonas species. This suggests a continuous gene flux between related xanthomonads associated with diverse plant hosts that results in the emergence of novel pathogen lineages and associated phenotypes, including host range.
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Molecular Epidemiology of Xanthomonas perforans Outbreaks in Tomato Plants from Transplant to Field as Determined by Single-Nucleotide Polymorphism Analysis. Appl Environ Microbiol 2019; 85:AEM.01220-19. [PMID: 31253682 DOI: 10.1128/aem.01220-19] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Accepted: 06/25/2019] [Indexed: 01/15/2023] Open
Abstract
Outbreaks of bacterial spot on tomato (BST) caused by Xanthomonas perforans are a major concern for sustainable crop production. BST is a common occurrence in tomato transplants grown for field production. We hypothesized that BST outbreaks in commercial fields originate from X. perforans strains inadvertently introduced from commercial transplant facilities. To test this hypothesis, we used a genome-wide single-nucleotide polymorphism (SNP) analysis to characterize X. perforans strains recovered from tomato transplant facilities and fields in commercial production areas. X. perforans strains were isolated from symptomatic transplants prior to roguing at two commercial transplant growers. Then, the same groups of transplants were tracked to commercial fields to recover X. perforans strains from diseased plants prior to harvest. Whole-genome sequencing was carried out on 84 strains isolated from transplant and field plants from Florida and South Carolina. SNPs were called using three reference strains that represented the genetic variation of the sampled strains. Field strains showing genetic similarity to transplant strains had a difference of 2 to 210 SNPs. Transplant and field strains clustered together by grower within each phylogenomic group, consistent with expectations. The range of genetic divergence among strains isolated from field plants was similar to the range obtained from strains on transplants. Using the range of genetic variation observed in transplants, we estimate that 60% to 100% of field strains were an extension of the transplant strain population. Our results stress the importance of BST management to reduce X. perforans movement from transplant to field and to minimize subsequent disease outbreaks.IMPORTANCE Current management of Xanthomonas perforans on tomato plants mainly relies on the frequent application of pesticides. However, the lack of effective pesticides and the development of strain tolerance to certain bactericides limit the ability to control outbreaks in production fields. Better knowledge of probable sources of X. perforans inoculum during tomato production is required to refine management strategies. Tomato plants are typically established in the field using transplants. This study aimed to determine if strains from field epidemics were coming from transplant facilities or resulted from local field outbreaks. The overall goal was to identify potential sources of inoculum and subsequently develop strategies to reduce carryover from transplant production to the field. Our results indicate that tomato producers should shift disease management efforts to transplant facilities to reduce disease in the field. Improved transplant health should reduce the likelihood of bacterial spot outbreaks and subsequently reduce pesticide usage in the field.
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