A phloem-limited RNA phytovirus infection does not positively modulate vector preference and fitness in primary and alternate hosts

Colonizing aphids play an important role in the transmission of RNA phytoviruses in the family Solemoviridae. According to "host manipulation hypothesis," phloem limited and persistently transmitted Solemoviridae viruses modulate host physiology that positively affects vector behavior and fitness and facilitates virus spread. However, it is unclear if virus-modulated host effects on vectors across pathosystems involving Solemoviridae members are always positive. Cotton leafroll dwarf virus (CLRDV) is a recently introduced Solemoviridae member in the United States, and it is transmitted by the cotton aphid (Aphis gossypii). Effects of CLRDV infection on vector behavior and fitness were evaluated on its primary host plant, cotton (Gossypium hirsutum), and an alternate host plant, hibiscus (Hibiscus acetosella). In this study, changes to viruliferous and non-viruliferous aphid preference and aphid fitness on virus-infected and non-infected hosts were examined. In contrast to the hypothesized preference of non-viruliferous aphids for infected plants and vice-versa, both viruliferous and non-viruliferous A. gossypii preferred non-infected cotton and hibiscus plants over CLRDV-infected plants. This suggested that the preference of non-viruliferous vectors to non-infected plants might negatively impact virus acquisition, whereas the preference of viruliferous vectors toward non-infected plants could positively facilitate virus inoculation. The total fecundity and intrinsic rate of increase of aphids were higher on non-infected plants compared with CLRDV-infected plants. The lack of enhanced fitness benefits on CLRDV-infected hosts also could negatively impact virus spread. Overall, this study suggested that "host manipulation hypothesis" favoring vector attraction and enhanced fitness on infected plants does not apply to all pathosystems involving Solemoviridae members.