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Suffert F, Goyeau H, Sache I, Carpentier F, Gélisse S, Morais D, Delestre G. Epidemiological trade-off between intra- and interannual scales in the evolution of aggressiveness in a local plant pathogen population. Evol Appl 2018; 11:768-780. [PMID: 29875818 PMCID: PMC5979725 DOI: 10.1111/eva.12588] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2017] [Accepted: 11/30/2017] [Indexed: 01/15/2023] Open
Abstract
The efficiency of plant resistance to fungal pathogen populations is expected to decrease over time, due to their evolution with an increase in the frequency of virulent or highly aggressive strains. This dynamics may differ depending on the scale investigated (annual or pluriannual), particularly for annual crop pathogens with both sexual and asexual reproduction cycles. We assessed this time-scale effect, by comparing aggressiveness changes in a local Zymoseptoria tritici population over an 8-month cropping season and a 6-year period of wheat monoculture. We collected two pairs of subpopulations to represent the annual and pluriannual scales: from leaf lesions at the beginning and end of a single annual epidemic and from crop debris at the beginning and end of a 6-year period. We assessed two aggressiveness traits-latent period and lesion size-on sympatric and allopatric host varieties. A trend toward decreased latent period concomitant with a significant loss of variability was established during the course of the annual epidemic, but not over the 6-year period. Furthermore, a significant cultivar effect (sympatric vs. allopatric) on the average aggressiveness of the isolates revealed host adaptation, arguing that the observed patterns could result from selection. We thus provide an experimental body of evidence of an epidemiological trade-off between the intra- and interannual scales in the evolution of aggressiveness in a local plant pathogen population. More aggressive isolates were collected from upper leaves, on which disease severity is usually lower than on the lower part of the plants left in the field as crop debris after harvest. We suggest that these isolates play little role in sexual reproduction, due to an Allee effect (difficulty finding mates at low pathogen densities), particularly as the upper parts of the plant are removed from the field, explaining the lack of transmission of increases in aggressiveness between epidemics.
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Affiliation(s)
- Frédéric Suffert
- UMR BIOGER, INRA, AgroParisTechUniversité Paris‐SaclayThiverval‐GrignonFrance
| | - Henriette Goyeau
- UMR BIOGER, INRA, AgroParisTechUniversité Paris‐SaclayThiverval‐GrignonFrance
| | - Ivan Sache
- UMR BIOGER, INRA, AgroParisTechUniversité Paris‐SaclayThiverval‐GrignonFrance
| | - Florence Carpentier
- UMR BIOGER, INRA, AgroParisTechUniversité Paris‐SaclayThiverval‐GrignonFrance
| | - Sandrine Gélisse
- UMR BIOGER, INRA, AgroParisTechUniversité Paris‐SaclayThiverval‐GrignonFrance
| | - David Morais
- UMR BIOGER, INRA, AgroParisTechUniversité Paris‐SaclayThiverval‐GrignonFrance
| | - Ghislain Delestre
- UMR BIOGER, INRA, AgroParisTechUniversité Paris‐SaclayThiverval‐GrignonFrance
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Mehmood Y, Sambasivam P, Kaur S, Davidson J, Leo AE, Hobson K, Linde CC, Moore K, Brownlie J, Ford R. Evidence and Consequence of a Highly Adapted Clonal Haplotype within the Australian Ascochyta rabiei Population. FRONTIERS IN PLANT SCIENCE 2017; 8:1029. [PMID: 28670320 PMCID: PMC5472848 DOI: 10.3389/fpls.2017.01029] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2017] [Accepted: 05/29/2017] [Indexed: 05/21/2023]
Abstract
The Australian Ascochyta rabiei (Pass.) Labr. (syn. Phoma rabiei) population has low genotypic diversity with only one mating type detected to date, potentially precluding substantial evolution through recombination. However, a large diversity in aggressiveness exists. In an effort to better understand the risk from selective adaptation to currently used resistance sources and chemical control strategies, the population was examined in detail. For this, a total of 598 isolates were quasi-hierarchically sampled between 2013 and 2015 across all major Australian chickpea growing regions and commonly grown host genotypes. Although a large number of haplotypes were identified (66) through short sequence repeat (SSR) genotyping, overall low gene diversity (Hexp = 0.066) and genotypic diversity (D = 0.57) was detected. Almost 70% of the isolates assessed were of a single dominant haplotype (ARH01). Disease screening on a differential host set, including three commonly deployed resistance sources, revealed distinct aggressiveness among the isolates, with 17% of all isolates identified as highly aggressive. Almost 75% of these were of the ARH01 haplotype. A similar pattern was observed at the host level, with 46% of all isolates collected from the commonly grown host genotype Genesis090 (classified as "resistant" during the term of collection) identified as highly aggressive. Of these, 63% belonged to the ARH01 haplotype. In conclusion, the ARH01 haplotype represents a significant risk to the Australian chickpea industry, being not only widely adapted to the diverse agro-geographical environments of the Australian chickpea growing regions, but also containing a disproportionately large number of aggressive isolates, indicating fitness to survive and replicate on the best resistance sources in the Australian germplasm.
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Affiliation(s)
- Yasir Mehmood
- Environmental Futures Research Institute, School of Natural Sciences, Griffith University, NathanQLD, Australia
| | - Prabhakaran Sambasivam
- Environmental Futures Research Institute, School of Natural Sciences, Griffith University, NathanQLD, Australia
| | - Sukhjiwan Kaur
- Agriculture Victoria, AgriBio, The Centre for AgriBioscience, BundooraVIC, Australia
| | - Jenny Davidson
- South Australian Research and Development Institute, UrrbraeSA, Australia
| | - Audrey E. Leo
- New South Wales Department of Primary Industries, Wagga Wagga Agricultural Institute, Wagga WaggaNSW, Australia
| | - Kristy Hobson
- Department of Primary Industries, Tamworth Agricultural Institute, TamworthNSW, Australia
| | - Celeste C. Linde
- Research School of Biology, Australian National University, CanberraACT, Australia
| | - Kevin Moore
- Department of Primary Industries, Tamworth Agricultural Institute, TamworthNSW, Australia
| | - Jeremy Brownlie
- Environmental Futures Research Institute, School of Natural Sciences, Griffith University, NathanQLD, Australia
| | - Rebecca Ford
- Environmental Futures Research Institute, School of Natural Sciences, Griffith University, NathanQLD, Australia
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