Data from: Virus adaptation to quantitative plant resistance: erosion or breakdown?

Adaptation of populations to new environments is frequently costly due to trade-offs between life history traits, and consequently, parasites are expected to be locally adapted to sympatric hosts. Also, during adaptation to the host, an increase of parasite fitness could have direct consequences on its aggressiveness (i.e. the quantity of damages caused to the host by the virus). These two phenomena have been observed in the context of pathogen adaptation to host qualitative and monogenic resistances. However, the ability of pathogens to adapt to quantitative polygenic plant resistances and the consequences of these potential adaptations on other pathogen life history traits remain to be evaluated. Using Potato virus Y and two pepper genotypes (one susceptible and one with quantitative resistance), experimental evolutions showed that adaptation to a quantitative resistance was possible and resulted in resistance breakdown. This adaptation was associated to a fitness cost on the susceptible cultivar, but had no consequence neither in terms of aggressiveness, which could be explained by a high tolerance level, nor in terms of aphid transmission efficiency. It results that quantitative resistances are not necessarily durable but management strategies mixing susceptible and resistant cultivars in space and/or in time should be useful to preserve their efficiency.

种群对新环境的适应往往伴随着适应性代价，这源于生活史性状间的权衡关系；因此，寄生虫理论上应进化出对同域寄主的本地适应性。此外，在适应寄主的过程中，寄生虫适合度的提升可能直接影响其致病力——即病毒对寄主造成的损害程度。这两种现象已在病原物适应寄主质量抗性（qualitative resistance）与单基因抗性（monogenic resistances）的研究中被观测到。然而，病原物对植物数量多基因抗性（quantitative polygenic plant resistances）的适应能力，以及这类潜在适应对病原物其他生活史性状带来的影响，仍有待进一步评估。本研究以马铃薯Y病毒（Potato virus Y）与两种辣椒基因型（一种为感病基因型，另一种携带数量抗性）为材料，通过实验进化研究发现，病原物对数量抗性的适应是可行的，且可导致寄主抗性的突破（resistance breakdown）。这种适应与感病品种上的适合度代价（fitness cost）相关，但无论在致病力层面（这一现象可通过寄主的高耐受水平解释）还是蚜虫传毒效率（aphid transmission efficiency）层面，均未产生显著影响。由此可见，植物数量抗性并非必然具有持久性，但通过时空混合种植感病与抗病品种的防控策略，或可有效维持该抗性的应用效能。