Data from: Investigating the production of sexual resting structures in a plant pathogen reveals unexpected self-fertility and genotype-by-environment effects

The sexual stage of pathogens governs recombination patterns and often also provides means of surviving the off-season. Despite its importance for evolutionary potential and between-season epidemiology, sexual systems have not been carefully investigated for many important pathogens, and what generates variation in successful sexual reproduction of pathogens remains unexplored. We surveyed the sexually produced resting structures (chasmothecia) across 86 natural populations of fungal pathogen Podosphaera plantaginis (Ascomycota) naturally infecting Plantago lanceolata in the Åland archipelago, southwest of Finland. For this pathosystem, these resting structures are a key life-history stage, as more than half of the local pathogen populations go extinct every winter. We uncovered substantial variation in the level of chasmothecia produced among populations, ranging from complete absence to presence on all infected leaves. We found that chasmothecia developed within clonal isolates (single strain cultures). Additionally, these clonal isolates all contained both MAT1-1-1 and MAT1-2-1 genes that characterize mating-types in Ascomycetes. Hence, contrary to expectations, we conclude that this species is capable of haploid selfing. In controlled inoculations we discovered that pathogen genotypes varied in their tendency to produce chasmothecia. Production of chasmothecia was also affected by ambient temperature (E), and by the interaction between temperature and pathogen genotype (G × E). These G, E and G × E effects found both at a European scale, as well as within Åland, may partly explain the high variability observed among populations in chasmothecia levels. Consequently, they may be key drivers of the evolutionary potential and epidemiology of this highly dynamic pathosystem.病原体的有性阶段不仅调控重组模式，通常还为其度过淡季提供生存途径。尽管有性阶段对病原体的进化潜力和季间流行病学具有重要意义，但众多重要病原体的有性系统尚未得到细致研究，而驱动病原体成功有性生殖产生变异的机制仍未得到深入解析。我们针对芬兰西南部奥兰群岛（Åland archipelago）中自然侵染长叶车前草（Plantago lanceolata）的子囊菌门（Ascomycota）真菌病原体车前单囊壳（Podosphaera plantaginis）的86个自然种群，开展了有性生殖产生的休眠结构——闭囊壳（chasmothecia）的调查。对于该病害系统（pathosystem）而言，这类休眠结构是关键的生活史阶段：每年冬季有超过半数的本地病原体种群会发生灭绝。我们发现不同种群间的闭囊壳产出水平存在显著差异，从完全无闭囊壳到所有染病叶片均带有闭囊壳不等。研究还观测到，闭囊壳可在克隆分离株（单菌株培养物）中形成。此外，这些克隆分离株均携带表征子囊菌交配型的MAT1-1-1与MAT1-2-1基因。因此，与此前学界预期相悖，我们推断该物种具备单倍体自交（haploid selfing）能力。在可控接种实验中，我们发现不同病原体基因型的闭囊壳产出倾向存在显著差异。闭囊壳的产出同时受环境温度（E）以及病原体基因型与温度的互作效应（G × E）影响。这类基因型（G）、环境（E）以及G×E效应，在欧洲尺度及奥兰群岛内部均被检测到，这或许可以部分解释不同种群间闭囊壳水平的高度变异。综上，这些因素可能是驱动这一高度动态病害系统进化潜力与流行病学特征的关键因素。