Functions Of Geminiviruses In Tri-Trophic Interactions Of Plant-Bemisia Tabaci-Eretmocerus Hayati

The tobacco whitefly Bemisia tabaci and geminiviruses it transmits are important pests in many crops such as vegetables and ornamental vegetations. In recent years, studies on vector Bemisia tabaci-geminiviruses-host plant tripartite relationship have attracted increasing research interests. Meanwhile, much work has been done on host plant-whitefly-parasitoid interactions. However, the impact of plant viruses has been rarely considered in this tritrophic system. In this paper, with study system of two geminiviruses, i.e. tomato yellow leaf curl virus (TYLCV) and tomato yellow leaf curl China virus (TYLCCNV), host plant tomato, Middle East-Asia Minor1(MEAM1) whitefly and its parasitoid, Eretmocerus hayati (Zolnerowich and Rose), we tested the effects of plant viruses on olfactory response and host choice behaviors of B. tabaci and E. hayati, on foraging performance and fitness of E. hayati. We also investigate the effects of TYLCCNV infected tobacco on olfactory response and host choice behaviors of B. tabaci and E. hayati, as this is a good example of tobacco mediated indirect mutualism between ME AMI whitefly and TYLCCNV. The main results are summarized as follows.(1) Effects of viral infection of plants on olfactory response of B. tabaci:TYLCCNV infected tomato and tobacco showed significant attraction to whiteflies, in comparison with non-viruliferous plant. However, the attraction became weaker when plants were co-infested by whitefly and virus, in comparison with whitefly-infested plant. TYLCV infected tomato had no significant arrtaction to whiteflies, but the combination of virus infection and whitefly infestation showed significant arrtaction to whiteflies, in comparison with whitfely-infested plant.(2) Effects of viral infection of plants on olfactory response of E. hayati:in comparison with blank control, the parasitoid, E. hayati intend to respond to plant odours, no matter it is infested by pest or not. In choice experiments between plants with or without virus/whitefly infection, the olfactory response of E. hayati depend on the combination of plant species and begomoviruse. Both TYLCV infected tomato and TYLCCNV infected tobacco showed significant attraction to the parasitoid, however, TYLCCNV infected tomato had no signficant arrtaction to E. hayati.(3) TYLCV-infected tomato led to a significant increase of leaf trichome density, which in TYLCV-infected plants was1.8times that in uninfected plants. However, no significant changes in the TYLCCNV-infected tomato leaf trichome density. The host handling time and patch residence time of the parasitoid on TYLCV-infected plants were2and1.5-fold that on uninfected plants respectively. However, the parasitism rates, emergence rates and developmental durations of the parasitoid on TYLCV-infected and uninfected plants were similar. The host handling time, patch residence time, parasitism rates, emergence rates and developmental durations of the parasitoid of TYLCCNV-infected plants and on uninfected plants are no significant differences.To our knowledge, this is the first report of begomovirus-induced increase of plant leaf trichomes and its effects on a parasitoid, providing new data for understanding the interactions between plants, begomoviruses, whiteflies and parasitoids. The data here also indicated the complexity of plant-virus-vector-natural enemy interactions and thus need further study for understanding their relationships.