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Galvañ A, Boughalleb-M'Hamdi N, Benfradj N, Mannai S, Lázaro E, Vicent A. Climate suitability of the Mediterranean Basin for citrus black spot disease (Phyllosticta citricarpa) based on a generic infection model. Sci Rep 2022; 12:19876. [PMID: 36400797 PMCID: PMC9674692 DOI: 10.1038/s41598-022-22775-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 10/19/2022] [Indexed: 11/21/2022] Open
Abstract
Citrus black spot (CBS), caused by the fungus Phyllosticta citricarpa, is associated with serious yield and quality losses. The climate suitability of the Mediterranean Basin for CBS development has been long debated. However, CBS has been described in Tunisia. In this study, a generic model was used to simulate potential infections by ascospores and pycnidiospores together with a degree-day model to predict the onset of ascospore release. High-resolution climatic data were retrieved from the ERA5-Land dataset for the citrus-growing regions in the Mediterranean Basin and other locations where CBS is present. In general, the onset of ascospore release was predicted to occur late in spring, but there is no agreement on the adequacy of this empirical model for extrapolation to the Mediterranean Basin. The generic model indicated that infections by ascospores and pycnidiospores would be concentrated mainly in autumn, as well as in spring for pycnidiospores. In contrast to previous studies, the percentage of hours suitable for infection was higher for pycnidiospores than for ascospores. The values obtained with the generic infection model for Tunisia and several CBS-affected locations worldwide were similar to those for other citrus-growing regions in Europe and Northern Africa. These results support previous work indicating that the climate of the Mediterranean Basin is suitable for CBS development.
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Affiliation(s)
- Anaïs Galvañ
- Institut Valencià d'Investigacions Agràries (IVIA), Centre de Protecció Vegetal i Biotecnologia, 46113, Moncada, Valencia, Spain
| | - Naima Boughalleb-M'Hamdi
- Department of Biological Sciences and Plant Protection, Institut Supérieur Agronomique de Chott Mariem, LR21AGR05, University of Sousse, Chott Mariem, Sousse, 4042, Tunisia
| | - Najwa Benfradj
- Department of Biological Sciences and Plant Protection, Institut Supérieur Agronomique de Chott Mariem, LR21AGR05, University of Sousse, Chott Mariem, Sousse, 4042, Tunisia
| | - Sabrine Mannai
- Department of Biological Sciences and Plant Protection, Institut Supérieur Agronomique de Chott Mariem, LR21AGR05, University of Sousse, Chott Mariem, Sousse, 4042, Tunisia
| | - Elena Lázaro
- Institut Valencià d'Investigacions Agràries (IVIA), Centre de Protecció Vegetal i Biotecnologia, 46113, Moncada, Valencia, Spain
| | - Antonio Vicent
- Institut Valencià d'Investigacions Agràries (IVIA), Centre de Protecció Vegetal i Biotecnologia, 46113, Moncada, Valencia, Spain.
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Discerning the global phylogeographic distribution of Phyllosticta citricarpa by means of whole genome sequencing. Fungal Genet Biol 2022; 162:103727. [PMID: 35870700 DOI: 10.1016/j.fgb.2022.103727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 07/08/2022] [Accepted: 07/18/2022] [Indexed: 11/24/2022]
Abstract
Phyllosticta citricarpa is a fungal pathogen causing citrus black spot (CBS). As a regulated pest in some countries, the presence of the pathogen limits the export of fruit and is therefore of agricultural and economic importance. In this study, we used high throughput sequencing data to infer the global phylogeographic distribution of this pathogen, including 71 isolates from eight countries, Argentina, Australia, Brazil, China, Cuba, Eswatini, South Africa and the United States of America. We assembled draft genomes and used a pairwise read mapping approach for the detection and enumeration of variants between isolates. We performed SSR marker discovery based on the assembled genome with the best assembly statistics, and generated genotype profiles for all isolates with 1987 SSR markers in silico. Furthermore, we identified 32,560 SNPs relative to a reference sequence followed by population genetic analyses based on the three datasets; pairwise variant counts, SSR genotypes and SNP genotypes. All three analysis approaches gave similar overall results. Possible pathways of dissemination among the populations from China, Australia, southern Africa and the Americas are postulated. The Chinese population is the most diverse, and is genetically the furthest removed from all other populations, and is therefore considered the closest to the origin of the pathogen. Isolates from Australia, Eswatini and the South African province Mpumalanga are closely associated and clustered together with those from Argentina and Brazil. The Eastern Cape, North West, and KwaZulu-Natal populations in South Africa grouped in another cluster, while isolates from Limpopo are distributed between the two aforementioned clusters. Southern African populations showed a close relationship to populations in North America, and could be a possible source of P. citricarpa populations that are now found in North America. This study represents the largest whole genome sequencing survey of P. citricarpa to date and provides a more comprehensive assessment of the population genetic diversity and connectivity of P. citricarpa from different geographic origins. This information could further assist in a better understanding of the epidemiology of the CBS pathogen, its long-distance dispersal and dissemination pathways, and can be used to refine phytosanitary regulations and management programmes for the disease.
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Iantas J, Savi DC, Schibelbein RDS, Noriler SA, Assad BM, Dilarri G, Ferreira H, Rohr J, Thorson JS, Shaaban KA, Glienke C. Endophytes of Brazilian Medicinal Plants With Activity Against Phytopathogens. Front Microbiol 2021; 12:714750. [PMID: 34539608 PMCID: PMC8442585 DOI: 10.3389/fmicb.2021.714750] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Accepted: 08/03/2021] [Indexed: 12/14/2022] Open
Abstract
Plant diseases caused by phytopathogens are responsible for significant crop losses worldwide. Resistance induction and biological control have been exploited in agriculture due to their enormous potential. In this study, we investigated the antimicrobial potential of endophytic fungi of leaves and petioles of medicinal plants Vochysia divergens and Stryphnodendron adstringens located in two regions of high diversity in Brazil, Pantanal, and Cerrado, respectively. We recovered 1,304 fungal isolates and based on the characteristics of the culture, were assigned to 159 phenotypes. One isolate was selected as representative of each phenotype and studied for antimicrobial activity against phytopathogens. Isolates with better biological activities were identified based on DNA sequences and phylogenetic analyzes. Among the 159 representative isolates, extracts from 12 endophytes that inhibited the mycelial growth (IG) of Colletotrichum abscissum (≥40%) were selected to expand the antimicrobial analysis. The minimum inhibitory concentrations (MIC) of the extracts were determined against citrus pathogens, C. abscissum, Phyllosticta citricarpa and Xanthomonas citri subsp. citri and the maize pathogen Fusarium graminearum. The highest activity against C. abscissum were from extracts of Pseudofusicoccum stromaticum CMRP4328 (IG: 83% and MIC: 40 μg/mL) and Diaporthe vochysiae CMRP4322 (IG: 75% and MIC: 1 μg/mL), both extracts also inhibited the development of post-bloom fruit drop symptoms in citrus flowers. The extracts were promising in inhibiting the mycelial growth of P. citricarpa and reducing the production of pycnidia in citrus leaves. Among the isolates that showed activity, the genus Diaporthe was the most common, including the new species D. cerradensis described in this study. In addition, high performance liquid chromatography, UV detection, and mass spectrometry and thin layer chromatography analyzes of extracts produced by endophytes that showed high activity, indicated D. vochysiae CMRP4322 and P. stromaticum CMRP4328 as promising strains that produce new bioactive natural products. We report here the capacity of endophytic fungi of medicinal plants to produce secondary metabolites with biological activities against phytopathogenic fungi and bacteria. The description of the new species D. cerradensis, reinforces the ability of medicinal plants found in Brazil to host a diverse group of fungi with biotechnological potential.
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Affiliation(s)
- Jucélia Iantas
- Postgraduate Program of Microbiology, Parasitology and Pathology, Department of Pathology, Federal University of Paraná, Curitiba, Brazil
| | - Daiani Cristina Savi
- Department of Biomedicine, Centro Universitário Católica de Santa Catarina, Joinville, Brazil
- Postgraduate Program of Genetics, Federal University of Paraná, Curitiba, Brazil
| | - Renata da Silva Schibelbein
- Postgraduate Program of Microbiology, Parasitology and Pathology, Department of Pathology, Federal University of Paraná, Curitiba, Brazil
| | - Sandriele Aparecida Noriler
- Postgraduate Program of Microbiology, Parasitology and Pathology, Department of Pathology, Federal University of Paraná, Curitiba, Brazil
| | | | - Guilherme Dilarri
- Department of General and Applied Biology, Biosciences Institute, State University of São Paulo, Rio Claro, Brazil
| | - Henrique Ferreira
- Department of General and Applied Biology, Biosciences Institute, State University of São Paulo, Rio Claro, Brazil
| | - Jürgen Rohr
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY, United States
| | - Jon S. Thorson
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY, United States
- Center for Pharmaceutical Research and Innovation, College of Pharmacy, University of Kentucky, Lexington, KY, United States
| | - Khaled A. Shaaban
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY, United States
- Center for Pharmaceutical Research and Innovation, College of Pharmacy, University of Kentucky, Lexington, KY, United States
| | - Chirlei Glienke
- Postgraduate Program of Microbiology, Parasitology and Pathology, Department of Pathology, Federal University of Paraná, Curitiba, Brazil
- Postgraduate Program of Genetics, Federal University of Paraná, Curitiba, Brazil
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Moyo P, Fourie PH, Masikane SL, de Oliveira Fialho R, Mamba LC, du Plooy W, Hattingh V. The Effects of Postharvest Treatments and Sunlight Exposure on the Reproductive Capability and Viability of Phyllosticta citricarpa in Citrus Black Spot Fruit Lesions. PLANTS (BASEL, SWITZERLAND) 2020; 9:E1813. [PMID: 33371400 PMCID: PMC7767452 DOI: 10.3390/plants9121813] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 12/12/2020] [Accepted: 12/16/2020] [Indexed: 11/17/2022]
Abstract
Citrus black spot (CBS) is caused by Phyllosticta citricarpa, which is classified as a quarantine organism in certain countries whose concerns are that CBS-infected fruit may be a pathway for introduction of the pathogen. This study evaluated the reproductive capability and viability of P. citricarpa under simulated conditions in which the whole fruit, peel segments, or citrus pulp with CBS lesions were discarded. Naturally infected 'Midknight' Valencia orange and 'Eureka' lemon fruit, either treated using standard postharvest sanitation, fungicide, and wax coating treatments or untreated, were placed into cold storage for 5 weeks (oranges at 4 °C and lemons at 7 °C). Thereafter, treated and untreated fruit were incubated for a further 2 weeks at conditions conducive for CBS symptom expression and formation of pycnidia. The ability of pycnidia to secrete viable pycnidiospores after whole fruit and peel segments or peel pieces from citrus pulp were exposed to sunlight at warm temperatures (±28 °C) and ±75% relative humidity levels was then investigated. The combination of postharvest treatments and cold storage effectively controlled CBS latent infections (>83.6% control) and pycnidium formation (<1.4% of lesions formed pycnidia), and the wax coating completely inhibited pycnidiospore release in fruit and peel segments. Pycnidiospores were secreted only from lesions on untreated fruit and peel segments and at low levels (4.3-8.6%) from peel pieces from pulped treated fruit. However, spore release rapidly declined when exposed to sunlight conditions (1.4% and 0% after 2 and 3 days, respectively). The generally poor reproductive ability and viability of CBS fruit lesions on harvested fruit, particularly when exposed to sunlight conditions, supports the conclusion that citrus fruit without leaves is not an epidemiologically significant pathway for the entry, establishment, and spread of P. citricarpa.
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Affiliation(s)
- Providence Moyo
- Citrus Research International, P.O. Box 28, Nelspruit 1200, South Africa; (P.H.F.); (S.L.M.); (L.C.M.); (W.d.P.); (V.H.)
| | - Paul H. Fourie
- Citrus Research International, P.O. Box 28, Nelspruit 1200, South Africa; (P.H.F.); (S.L.M.); (L.C.M.); (W.d.P.); (V.H.)
- Department of Plant Pathology, Stellenbosch University, Private Bag X1, Stellenbosch 7602, South Africa
| | - Siyethemba L. Masikane
- Citrus Research International, P.O. Box 28, Nelspruit 1200, South Africa; (P.H.F.); (S.L.M.); (L.C.M.); (W.d.P.); (V.H.)
| | - Régis de Oliveira Fialho
- Department of Plant Pathology and Nematology, University of São Paulo, Piracicaba 13418-900, SP, Brazil;
| | - Lindokuhle C. Mamba
- Citrus Research International, P.O. Box 28, Nelspruit 1200, South Africa; (P.H.F.); (S.L.M.); (L.C.M.); (W.d.P.); (V.H.)
| | - Wilma du Plooy
- Citrus Research International, P.O. Box 28, Nelspruit 1200, South Africa; (P.H.F.); (S.L.M.); (L.C.M.); (W.d.P.); (V.H.)
| | - Vaughan Hattingh
- Citrus Research International, P.O. Box 28, Nelspruit 1200, South Africa; (P.H.F.); (S.L.M.); (L.C.M.); (W.d.P.); (V.H.)
- Department of Horticultural Science, University of Stellenbosch, Private Bag X1, Stellenbosch 7602, South Africa
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Moyo P, du Raan S, Fourie PH. Models for predicting pseudothecium maturity and ascospore release of Phyllosticta spp. in South African citrus orchards. S AFR J SCI 2020. [DOI: 10.17159/sajs.2020/7955] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
Ascosporic infection plays a major role in the epidemiology of citrus black spot (CBS) in South Africa, a disease caused by Phyllosticta citricarpa. Phyllosticta pseudothecium maturation and ascospore release models have been integrated in infection models to predict the availability of the primary inoculum source. However, these models have not been validated on a broader data set and this study aimed to validate and improve these epidemiological models. New pseudothecium maturation and ascospore release models for P. citricarpa were developed, based on weather and ascospore trap data from 13 locations and up to five seasons. From the 29 data sets analysed, 3775 3-hourly periods with ascospore events were recorded on 1798 days; 90% of these events occurred between 16.0 °C and 32.1 °C (daily Tmin and Tmax of 15.4 °C and 33.5 °C, respectively) and 75% occurred above a relative humidity (RH) of 55.9% (daily RH > 47.9%). Rain was recorded during 13.8% of these ascospore events and 20.0% of ascospore days. Using logistic regression, a Gompertz model that best predicted pseudothecium maturation, or the probability of onset of ascospore release, was developed and was markedly more accurate than the previously described models. The model consisted of DDtemp [cumulative degree-days from midwinter (1 July) calculated as (minimum + maximum daily temperature) / 2 – 10 °C] and DDwet (DDtemp accumulated only on days with >0.1 mm rain or vapour pressure deficit <5 hPa) as variables in the formula: probability of first ascospore event = exp(-exp(-(-3.131 + 0.007 × DDtemp - 0.007 × DDwet))). A Gompertz model [PAT = exp(-2.452 × exp(-0.004 × DDwet2))] was also developed for ascospore release; DDwet2 = DDtemp accumulated, from first seasonal ascospore trap day, only on days with >0.1 mm rain or vapour pressure deficit <5 hPa. Similar to the DDwet2 model described in a previous study, this model adequately predicted the general trend in ascospore release but poorly predicted periods of daily, 3-day and 7-day ascospore peaks.
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Affiliation(s)
| | | | - Paul H. Fourie
- Citrus Research International, Nelspruit, South Africa
- Department of Plant Pathology, Stellenbosch University, Stellenbosch, South Africa
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Tran NT, Miles AK, Dietzgen RG, Shuey TA, Mudge SR, Papacek D, Chandra KA, Drenth A. Inoculum Dynamics and Infection of Citrus Fruit by Phyllosticta citricarpa. PHYTOPATHOLOGY 2020; 110:1680-1692. [PMID: 32441591 DOI: 10.1094/phyto-02-20-0047-r] [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
Citrus black spot, caused by Phyllosticta citricarpa, is characterized by fruit blemishes and premature fruit drop, resulting in significant economic losses in summer rainfall areas. The pathogen forms both conidia and ascospores during its life cycle. However, the occurrence of these spores and their contributions to infection of fruit in field conditions are not well understood. Our research using direct leaf litter monitoring and volumetric spore trapping in Queensland orchards revealed that pseudothecia and ascospores in leaf litter as well as trapped ascospores had low abundance, while pycnidia and conidia were highly abundant. Both P. citricarpa and endophytic Phyllosticta spp. were identified, with P. citricarpa being dominant. In replicated field trials, we determined that infection of Imperial mandarin fruit by P. citricarpa occurred from fruit set until week 20 of fruit development, with the key infection events taking place between weeks 4 and 16 in Queensland subtropical conditions. These results demonstrate that protecting fruit during weeks 4 to 16 significantly reduced P. citricarpa infection. We found no significant correlation between the disease incidence in fruit and P. citricarpa conidial abundance in leaf litter or ascospore abundance measured by volumetric spore trapping. Therefore, it is suggested that inoculum sources in the tree canopy other than those detected by spore trapping and direct leaf litter monitoring may play a major role in the epidemiology of citrus black spot. Improved knowledge regarding epidemiology of P. citricarpa and an understanding of propagules causing infection may aid in development of more effective disease management strategies.
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Affiliation(s)
- Nga T Tran
- Centre for Horticultural Science, Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, Ecosciences Precinct, Dutton Park 4102, Queensland, Australia
| | - Andrew K Miles
- Centre for Horticultural Science, Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, Ecosciences Precinct, Dutton Park 4102, Queensland, Australia
| | - Ralf G Dietzgen
- Centre for Horticultural Science, QAAFI, The University of Queensland, Queensland Bioscience Precinct, St. Lucia 4072, Queensland, Australia
| | - Timothy A Shuey
- Centre for Horticultural Science, Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, Ecosciences Precinct, Dutton Park 4102, Queensland, Australia
| | - Stephen R Mudge
- Centre for Horticultural Science, Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, Ecosciences Precinct, Dutton Park 4102, Queensland, Australia
| | - Dan Papacek
- Bugs for Bugs, Glenvale 4350, Queensland, Australia
| | - Kerri A Chandra
- Queensland Department of Agriculture and Fisheries, Ecosciences Precinct, Dutton Park 4102, Queensland, Australia
| | - André Drenth
- Centre for Horticultural Science, Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, Ecosciences Precinct, Dutton Park 4102, Queensland, Australia
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