Data from: Adaptation of a plant pathogen to partial host resistance: selection for greater aggressiveness in grapevine downy mildew

An understanding of the evolution of pathogen quantitative traits in response to host selective pressures is essential for the development of durable management strategies for resistant crops. However, we still lack experimental data on the effects of partial host resistance on multiple phenotypic traits (aggressiveness) and evolutionary strategies in pathogens. We performed a cross-inoculation experiment with four grapevine hosts and 103 isolates of grapevine downy mildew (Plasmopara viticola) sampled from susceptible and partially resistant grapevine varieties. We analysed the neutral and adaptive genetic differentiation of five quantitative traits relating to pathogen transmission. Isolates from resistant hosts were more aggressive than isolates from susceptible hosts, as they had a shorter latency period and higher levels of spore production. This pattern of adaptation contrasted with the lack of neutral genetic differentiation, providing evidence for directional selection. No specificity for a particular host variety was detected. Adapted isolates had traits that were advantageous on all resistant varieties. There was no fitness cost associated with this genetic adaptation, but several trade-offs between pathogen traits were observed. These results should improve the accuracy of prediction of fitness trajectories for this biotrophic pathogen, an essential element for the modelling of durable deployment strategies for resistant varieties.

解析病原菌数量性状响应寄主选择压力的演化规律，是研发抗性作物持久管理策略的核心前提。然而，当前仍缺乏关于部分寄主抗性对病原菌多表型性状（致病力）及演化策略影响的实验数据。本研究以4种葡萄寄主与103株采自感病及部分抗病葡萄品种的葡萄霜霉菌（Plasmopara viticola）分离物为材料，开展交叉接种实验，分析了与病原菌传播相关的5个数量性状的中性遗传分化与适应性遗传分化。结果显示，来自抗病寄主的分离物致病力显著强于感病寄主来源的分离物，具体表现为潜育期更短、产孢量更高。该适应性演化模式与中性遗传分化缺失形成鲜明反差，为定向选择提供了直接实验证据。未检测到病原菌对特定寄主品种的专化性，适应性演化后的分离物在所有抗病品种上均表现出性状优势。本研究未观测到该遗传适应性伴随适合度代价，但发现病原菌多个性状间存在权衡关系。上述结果可提升该活体营养型病原菌适合度轨迹预测的准确性，而这正是构建抗性品种持久部署策略模型的关键要素。