title: Aggressiveness Changes in Populations of Didymella pinodes over Winter and Spring Pea Cropping Seasons.
abstract: Ascochyta blight, caused by the necrotrophic ascomycete Didymella pinodes, is responsible for severe losses in winter and spring pea crops. Despite different climatic conditions, epidemics on winter and spring crops are due to a single population of D. pinodes, suggesting gene flow either between the two crops or from reservoir sources during the cropping season. This should lead to similar pathogenicity characteristics in isolates sampled from the two crops. However, these hypotheses have never been formally tested. We therefore sampled a total of 520 D. pinodes strains throughout a growing season from winter and spring pea plots (WP and SP, respectively) and from winter and spring trap plants (TWP and TSP). Amplified fragment length polymorphism (AFLP) markers revealed high genetic diversity within subpopulations, whereas pathogenicity tests showed that mean aggressiveness increases over the course of an epidemic. These results support the idea that alloinoculum contributes to the carryover of epidemics between winter and spring crops and that the most aggressive isolates are selected as an epidemic progresses.
  
  
  
  Ascochyta blight, caused by Didymella pinodes, is responsible for severe losses in pea crops. While previous studies have shown that ascochyta blight epidemics on winter and spring crops are due to a single population of D. pinodes, suggesting that isolates from the two crops present similar pathogenicity characteristics, that hypothesis have never been tested. Genetic analysis of subpopulations sampled throughout a growing season from winter and spring pea plots revealed high genetic diversity within subpopulations, whereas pathogenicity tests showed that mean aggressiveness increases over the course of an epidemic.
authors.affiliation: INRA, UMR1349 Institut de Génétique, Environnement et Protection des Plantes (IGEPP), Domaine de la Motte, Le Rheu, France.
authors.forename: G
authors.initials: G
authors.lastname: Laloi
authors.affiliation: INRA, UMR1349 Institut de Génétique, Environnement et Protection des Plantes (IGEPP), Domaine de la Motte, Le Rheu, France.
authors.forename: J
authors.initials: J
authors.lastname: Montarry
authors.affiliation: INRA, UMR1349 Institut de Génétique, Environnement et Protection des Plantes (IGEPP), Domaine de la Motte, Le Rheu, France.
authors.forename: M
authors.initials: M
authors.lastname: Guibert
authors.affiliation: INRA, UMR1349 Institut de Génétique, Environnement et Protection des Plantes (IGEPP), Domaine de la Motte, Le Rheu, France.
authors.forename: D
authors.initials: D
authors.lastname: Andrivon
authors.affiliation: Agrocampus-Ouest, Laboratoire Ecologie et Santé des Plantes (ESP), Rennes, France.|INRA, UMR1069 Sol Agro et Hydrosystème Spatialisation (SAS), Rennes, France.
authors.forename: D
authors.initials: D
authors.lastname: Michot
authors.affiliation: INRA, UMR1349 Institut de Génétique, Environnement et Protection des Plantes (IGEPP), Domaine de la Motte, Le Rheu, France lemay@agrocampus-ouest.fr.|Agrocampus-Ouest, Laboratoire Ecologie et Santé des Plantes (ESP), Rennes, France.
authors.forename: C
authors.initials: C
authors.lastname: Le May
mesh_terms: D054458:Amplified Fragment Length Polymorphism Analysis; D001203:Ascomycota / Q000145:classification / Q000235:genetics / Q000254:growth & development* / Q000472:pathogenicity*; D014644:Genetic Variation; D018532:Pisum sativum / Q000382:microbiology*; D010935:Plant Diseases / Q000382:microbiology*; D012621:Seasons; D014774:Virulence