Data from: Outcomes of co-infection by two potyviruses: implications for the evolution of manipulative strategies

Recent studies have documented effects of plant-viruses on host plants that appear to enhance transmission by insect vectors. But, almost no empirical work has explored the implications of such apparent manipulation for interactions among co-infecting pathogens. We examined single and mixed infections of two potyviruses, Watermelon mosaic virus (WMV) and Zucchini yellow mosaic virus (ZYMV), that frequently co-occur in cucurbitaceae populations and share the same aphid vectors. We found that ZYMV isolates replicated at similar rates in single and mixed infections, while WMV strains accumulated to signficantly lower levels in the presence of ZYMV. Furthermore, ZYMV induced changes in leaf colour and volatile emissions that enhanced aphid (Aphis gossypii) recruitment to infected plants. In contrast, WMV did not elicit strong effects on plant-aphid interactions. Nevertheless, WMV was still readily transmitted from mixed infections, despite fairing poorly in in-plant competition. These findings suggest that pathogen effects on host-vector interactions may well influence competition among co-infecting pathogens. For example, if non-manipulative pathogens benefit from the increased vector traffic elicited by manipulative competitors, their costs of competition may be mitigated to some extent. Conversely, the benefits of manipulation may be limited by free-rider effects in systems where there is strong competition among pathogens for host resources and/or access to vectors.

现有研究已证实，植物病毒可对寄主植物产生调控效应，此类效应似乎能够提升昆虫介体的传毒效率。但目前几乎尚无实证研究探讨这类病毒调控行为对共侵染病原物间互作过程的潜在影响。本研究针对两种常于葫芦科（Cucurbitaceae）种群中复合侵染、且共享同一蚜虫介体的马铃薯Y病毒属病毒——西瓜花叶病毒（Watermelon mosaic virus, WMV）与南瓜黄化花叶病毒（Zucchini yellow mosaic virus, ZYMV）的单侵染与混合侵染状态展开了系统探究。研究结果显示，南瓜黄化花叶病毒（ZYMV）分离物在单侵染与混合侵染条件下的复制速率并无显著差异；而西瓜花叶病毒（WMV）株系在与南瓜黄化花叶病毒（ZYMV）共存时，其体内累积量显著降低。此外，南瓜黄化花叶病毒（ZYMV）可诱导寄主植物叶片色泽与挥发性挥发物组成发生改变，进而提升了棉蚜（Aphis gossypii）对染毒植株的趋附数量。与之相反，西瓜花叶病毒（WMV）并未对植物与蚜虫的互作产生显著调控效应。尽管西瓜花叶病毒（WMV）在寄主内的资源竞争中处于劣势，但它仍可从混合侵染的植株中顺利完成传毒。上述研究结果表明，病原物对寄主-介体互作的调控效应，极有可能会影响共侵染病原物之间的竞争关系。举例而言，若非调控型病原物能够借助调控型竞争者诱导的介体种群活跃度提升而获益，其竞争成本便可在一定程度上得到缓解。反之，在病原物之间存在强烈寄主资源竞争或介体获取竞争的生态系统中，调控型病原物的传毒收益可能会因搭便车效应（free-rider effects）而受到限制。