Lemaire Christophe, De Gracia Marie, Leroy Thibault, Michalecka Monika, Lindhard-Pedersen Hanne, Guerin Fabien, Gladieux Pierre, Le Cam Bruno
Université d'Angers, UMR1345 Institut de Recherche en Horticulture et Semences (IRHS), SFR4207 QUASAV, PRES L'UNAM, Angers, 49075, France.
INRA, UMR1345 Institut de Recherche en Horticulture et Semences (IRHS), Beaucouzé, 49071, France.
New Phytol. 2016 Feb;209(3):1220-9. doi: 10.1111/nph.13658. Epub 2015 Oct 2.
Plant pathogens adapt readily to new crop varieties in agrosystems, and it is crucial to understand the factors underlying the epidemic spread of new virulent strains if we are to develop more efficient strategies to control them. In this study we used multilocus microsatellite typing, molecular epidemiology tools and a large collection of isolates from cultivated, wild and ornamental apples to investigate the origin of new virulent populations of Venturia inaequalis, an ascomycete fungus causing apple scab on varieties carrying the Rvi6 resistance gene. We demonstrated a common origin at the European scale of populations infecting apples (Malus × domestica) carrying the Rvi6 resistance and Malus floribunda, the progenitor of the Rvi6 resistance. Demographic modeling indicated that the Rvi6-virulent lineage separated several thousands of years ago from populations infecting non-Rvi6 hosts, without detectable gene flow between the two lineages. These findings show that 'breakdowns' of plant resistance genes can be caused by the selection and migration of virulent genotypes from standing genetic variation maintained in environmental disease reservoirs, here ornamental crabapples. This work stresses the need to take better account of pathogen diversity in resistance screenings of breeding lines and in resistance deployment strategies, in order to enhance sustainable disease management.
植物病原体能迅速适应农业系统中的新作物品种，若要制定更有效的控制策略，了解新的致病菌株流行传播的潜在因素至关重要。在本研究中，我们使用多位点微卫星分型、分子流行病学工具以及从栽培苹果、野生苹果和观赏苹果中收集的大量分离株，来调查不等单囊壳菌（一种对携带Rvi6抗性基因的品种造成苹果黑星病的子囊菌真菌）新致病群体的起源。我们证明了在欧洲范围内，感染携带Rvi6抗性的苹果（苹果属杂交种）和Rvi6抗性的祖先多花海棠的群体有着共同起源。种群动态建模表明，具有Rvi6毒性的谱系在数千年前就与感染非Rvi6宿主的群体分离，两个谱系之间没有可检测到的基因流动。这些发现表明，植物抗性基因的“失效”可能是由于致病基因型从环境病害库（此处指观赏海棠）中维持的现有遗传变异中进行选择和迁移所致。这项工作强调，在育种系的抗性筛选和抗性部署策略中，需要更好地考虑病原体的多样性，以加强可持续的病害管理。
