For pathogens infecting single host species evolutionary trade-offs have previously been demonstrated between pathogen-induced mortality rates and transmission rates. It remains unclear, however, how such trade-offs impact sub-lethal pathogen-inflicted damage, and whether these trade-offs even occur in broad host-range pathogens. Here, we examine changes over the past 110 years in symptoms induced in maize by the broad host-range pathogen, maize streak virus (MSV). Specifically, we use the quantified symptom intensities of cloned MSV isolates in differentially resistant maize genotypes to phylogenetically infer ancestral symptom intensities and check for phylogenetic signal associated with these symptom intensities. We show that whereas symptoms reflecting harm to the host have remained constant or decreased, there has been an increase in how extensively MSV colonizes the cells upon which transmission vectors feed. This demonstrates an evolutionary trade-off between amounts of pathogen-inflicted harm and how effectively viruses position themselves within plants to enable onward transmission.

中文翻译：

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玉米条纹病毒出现后的症状演变

对于感染单个宿主物种的病原体，先前已经证明了病原体诱导的死亡率和传播率之间的进化折衷。然而，目前尚不清楚，这种权衡如何影响亚致死性致病菌所造成的损害，以及这些权衡是否在广泛的宿主范围病原体中发生。在这里，我们研究了过去110年中由广泛的宿主范围病原体玉米条纹病毒（MSV）引起的玉米症状的变化。具体而言，我们使用玉米抗病基因型差异的克隆MSV分离株的量化症状强度，以系统发育推断祖先症状强度，并检查与这些症状强度相关的系统发育信号。我们表明，尽管反映出对宿主有害的症状保持不变或有所减轻，MSV在传播载体赖以生存的细胞上定植的程度有所提高。这证明了在病原体造成的伤害数量与病毒如何有效地将自身定位在植物中以实现继续传播之间的进化权衡。