Specific and Spillover Effects on Vectors Following Infection of Two RNA Viruses in Pepper Plants

SIMPLE SUMMARY: Mixed infection of plant viruses is pervasive in agricultural systems. Mixed infection-induced host effects on vector/s fitness are often not well characterized. This study examined how infection of cucumber mosaic virus (CMV) and/or tomato spotted wilt orthotospovirus (TSWV) in pepper plants influenced the preference and fitness of their vectors Myzus persicae and Frankliniella fusca, respectively. Mixed infection resulted in more severe symptoms when compared with single infection. An antagonistic interaction between CMV and TSWV was also observed, wherein CMV titer was suppressed in mixed-infected compared with singly-infected plants. At instances, mixed-infected plants negatively impacted vector/s fitness more evidently than singly-infected plants. In others, the effects of mixed infection on vector preference or fitness did not vary from single infection. Overall, mixed infection in pepper plants did not enhance vector/s fitness and was not conductive to facilitate CMV and/or TSWV transmission and epidemics. The effects of CMV/TSWV infection extended to specific and non-specific vectors. CMV infection enhanced thrips fitness and TSWV infection enhanced aphid fitness. These spillover effects could result in crosstalk between vectors and viruses in the pathosystem, which in turn could lead to mixed infection. The driving forces of these interactions and the outcomes of these interactions remain to be characterized. ABSTRACT: Mixed infection of plant viruses is ubiquitous in nature and can affect virus–plant–vector interactions differently than single virus infection. While several studies have examined virus–virus interactions involving mixed virus infection, relatively few have examined effects of mixed virus infection on vector preference and fitness, especially when multiple vectors are involved. This study explored how single and mixed viral infection of a non-persistently transmitted cucumber mosaic virus (CMV) and propagative and persistently-transmitted tomato spotted wilt orthotospovirus (TSWV) in pepper, Capsicum annum L., influenced the preference and fitness of their vectors, the green peach aphid, Myzus persicae (Sulzer), and the tobacco thrips, Frankliniella fusca (Hinds), respectively. In general, mixed infected plants exhibited severe symptoms compared with individually infected plants. An antagonistic interaction between the two viruses was observed when CMV titer was reduced following mixed infection with TSWV in comparison with the single infection. TSWV titer did not differ between single and mixed infection. Myzus persicae settling preference and median developmental were not significantly different between CMV and/or TSWV-infected and non-infected plants. Moreover, M. persicae fecundity did not differ between CMV-infected and non-infected pepper plants. However, M. persicae fecundity was substantially greater on TSWV-infected plants than non-infected plants. Myzus persicae fecundity on mixed-infected plants was significantly lower than on singly-infected and non-infected plants. Frankliniella fusca fecundity was higher on CMV and/or TSWV-infected pepper plants than non-infected pepper plants. Furthermore, F. fusca-induced feeding damage was higher on TSWV-infected than on CMV-infected, mixed-infected, or non-infected pepper plants. Overall, our results indicate that the effects of mixed virus infection on vectors were not different from those observed following single virus infection. Virus-induced host phenotype-modulated effects were realized on both specific and non-specific vectors, suggesting crosstalk involving all vectors and viruses in this pathosystem. The driving forces of these interactions need to be further examined. The effects of interactions between two viruses and two vectors towards epidemics of one or both viruses also need to be examined.