Delmas Chloé E L, Dussert Yann, Delière Laurent, Couture Carole, Mazet Isabelle D, Richart Cervera Sylvie, Delmotte François
SAVE, Bordeaux Sciences Agro, INRA, 33140, Villenave d'Ornon, France.
Mol Ecol. 2017 Apr;26(7):1936-1951. doi: 10.1111/mec.14006. Epub 2017 Jan 27.
Adaptation produces hard or soft selective sweeps depending on the supply of adaptive genetic polymorphism. The evolution of pesticide resistance in parasites is a striking example of rapid adaptation that can shed light on selection processes. Plasmopara viticola, which causes grapevine downy mildew, forms large populations, in which resistance has rapidly evolved due to excessive fungicide use. We investigated the pathways by which fungicide resistance has evolved in this plant pathogen, to determine whether hard or soft selective sweeps were involved. An analysis of nucleotide polymorphism in 108 field isolates from the Bordeaux region revealed recurrent mutations of cytb and CesA3 conferring resistance to quinone outside inhibiting (QoI) and carboxylic acid amide (CAA) fungicides, respectively. Higher levels of genetic differentiation were observed for nucleotide positions involved in resistance than for neutral microsatellites, consistent with local adaptation of the pathogen to fungicide treatments. No hitchhiking was found between selected sites and neighbouring polymorphisms in cytb and CesA3, confirming multiple origins of resistance alleles. We assessed resistance costs, by evaluating the fitness of the 108 isolates through measurements of multiple quantitative pathogenicity traits under controlled conditions. No significant differences were found between sensitive and resistant isolates, suggesting that fitness costs may be absent or negligible. Our results indicate that the rapid evolution of fungicide resistance in P. viticola has involved a soft sweep.
适应会根据适应性遗传多态性的供应情况产生硬选择清除或软选择清除。寄生虫中抗药性的进化是快速适应的一个显著例子，它可以揭示选择过程。引起葡萄霜霉病的葡萄生单轴霉形成了大量种群，由于过度使用杀菌剂，其抗药性在这些种群中迅速进化。我们研究了这种植物病原体抗药性进化的途径，以确定是否涉及硬选择清除或软选择清除。对来自波尔多地区的108个田间分离株的核苷酸多态性分析表明，细胞色素b（cytb）和纤维素合成酶A3（CesA3）分别发生了反复突变，从而赋予了对醌外抑制剂（QoI）和羧酸酰胺（CAA）类杀菌剂的抗性。与中性微卫星相比，参与抗性的核苷酸位置观察到更高水平的遗传分化，这与病原体对杀菌剂处理的局部适应一致。在cytb和CesA3的选择位点与相邻多态性之间未发现搭便车现象，证实了抗性等位基因的多个起源。我们通过在受控条件下测量多个定量致病性性状来评估108个分离株的适合度，从而评估抗性代价。敏感分离株和抗性分离株之间未发现显著差异，这表明适合度代价可能不存在或可忽略不计。我们的结果表明，葡萄生单轴霉中杀菌剂抗性的快速进化涉及软选择清除。
