12: Mixed virus infection in a plant host and an insect vector and impacts on vector fitness and virus epidemics

Mixed virus infection in host plants and vectors can differentially alter the plant phenotype, influence vector preference and fitness. Whitefly-virus pathosystems in the southern United States include both the above-stated facets. For the first facet, we examined the effects of single and mixed infection of cucurbit leaf crumple virus (CuLCrV) and cucurbit yellow stunting disorder virus (CYSDV) infecting squash on whitefly, Bemisia tabaci host preference and fitness. Mixed infection of CuLCrV and CYSDV in squash plants severely altered their phenotype than single infection. The CYSDV load was reduced in mixed-infected squash plants than in singly-infected plants. Consequently, whiteflies acquired reduced amounts of CYSDV from mixed-infected plants than singly-infected plants. No differences were found for CuLCrV. Viruliferous (CuLCrV and/or CYSDV) whiteflies preferred non-infected plants over infected plants. CuLCrV and/or CYSDV infection didn’t affect B. tabaci fitness. For the second facet, we examined the effects of individual or combined acquisition of tomato yellow leaf curl virus (TYLCV) and CuLCrV on whitefly host preference and fitness. Whiteflies that acquired both CuLCrV and TYLCV had significantly lower CuLCrV load than whiteflies that acquired CuLCrV alone, whereas TYLCV load remained unaltered. Whitefly preference was not affected following individual or combined virus acquisition. Viruliferous (CuLCrV and/or TYLCV) whiteflies preferred to settle on non-infected plants. Presence of CuLCrV and/or TYLCV in whiteflies did not affect their fitness. Mixed virus infection in host plants and vectors could have implications for virus accumulation, virus acquisition, vector preference, and epidemics that sometimes are different from single-virus infection or acquisition.