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因生活史性状（life history traits）间的权衡而付出适应性代价，因此寄生物通常被认为会对其同域寄主（sympatric hosts）产生局部适应。此外，在适应寄主的过程中，寄生物适合度（parasite fitness）的提升可能直接影响其致病力（aggressiveness，即病毒对寄主造成的损害总量）。这两类现象已在病原物适应寄主定性单基因抗性（qualitative and monogenic resistances）的研究中被观测到。然而，病原物对定量多基因植物抗性（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产生的后续影响，仍有待进一步评估。本研究以马铃薯Y病毒（Potato virus Y）和两种辣椒基因型（一种为感病基因型，另一种携带定量抗性）为实验材料，通过实验演化研究发现，病原物对定量抗性的适应具备可行性，且可引发寄主抗性突破（resistance breakdown）。这类适应与感病品种上的适合度代价（fitness cost）相关，但既未对致病力产生影响（这一结果可通过较高的寄主耐受水平予以解释），也未对蚜虫传播效率（aphid transmission efficiency）造成显著影响。由此可见，定量抗性并非必然具备持久性，但通过空间或时间上混合种植感病与抗病品种的防控策略，应有助于维持该类抗性的应用效能。