Plant induced responses can change the preference and performance of subsequent herbivores by altering host plant traits. Chemical and morphological changes in plant phenotype are related to the type of damage caused by herbivores. For instance, plants damaged by phloem-feeding insects or pathogens induce different sets of plant responses than those induced by chewing insects. Although damage by multiple feeding guilds is common in nature, plant responses to feeding by multiple species are poorly understood, some simultaneous feeding may induce competing plant defense pathways. Then, despite the solid research developed trying to disentangle the effect of simultaneous feeding, few have attempted to investigate the effect of plant pathogen on their insect vector and on other herbivores. The aim of this study is to test whether the infection of different strain of plant virus affects: (i) the performance of a caterpillar (Trichoplusia ni) in terms of larva survival, growth rate, and leaf consumption; (ii) the population growth, number of offspring, and longevity of its vector aphids (Macrosiphum euphorbiae); (iii) the quality of host plants (Solanum lycopersicum). Plants were mechanically infected with three different strain of Potato Virus Y (NTN, NO and O) 10 days prior to bioassays. For caterpillar bioassays, plants were randomly assigned to one of the following treatments: control, aphid, NTN, NTN + aphids, NO, NO + aphids, O, O + aphids.
Results/Conclusions The highest growth rate was recorded on NTN strain- infected plants, followed by control plants, and the lowest performance was measure on NO and O strains, where the growth rate of T. ni was reduced by half comparing to caterpillar fed on NTN-infected plants. Similar results were found for leaf consumption; caterpillars ate more on control plants and NTN-infected plants than on NO and O-infected plants. The number of aphids on plants was positively affected by plant infection. More aphids were recorded on infected plants than on controls, no difference among strains was found. The number of offspring produce by an aphid was higher on NO-infected plants than on the other treatments. Virus strains affected both aphid and caterpillar performance and some strains had the opposite effect on these two herbivores. The opposite effects of strains on caterpillar and aphids may indicate the occurrence of crosstalk defense.