Changes in feeding behaviour are not related to the reduction in the transmission rate of plant viruses by Aphis gossypii (Homoptera: Aphididae) to melon plants colonized by Beauveria bassiana (Ascomycota: Hypocreales)

Abstract

Aphids are considered by far the most common and efficient vectors of non-persistent (NP) and persistent (P) plant viruses, with new, more environmentally friendly aphid control strategies urgently needed. Among these strategies, entomopathogenic fungi (EF) have successfully been employed against aphids mainly by foliar spray over infested crops. Plants benefit from not only their direct insecticidal activity on aphids but also a number of side outcomes of their application, such as sub-lethal effects on the target pest or their endophytic behaviour. Beyond aphid control, this endophytic quality has also been exploited to control diverse plant pathogenic microorganisms. In the present study, possible changes in cotton aphid (Aphis gossypii) probing and feeding behaviour mediated by the endophytic colonization of melon plants with Beauveria bassiana were studied using the electrical penetration graph (EPG) technique. Similarly, the effect of this endophytic colonization on P (Cucurbit aphid-borne yellows virus, Polerovirus) and NP (Cucumber mosaic virus, Cucumovirus) virus transmission by the cotton aphid was also studied. B. bassiana colonization did not alter the aphid feeding behaviour related to the NP or P virus inoculation process, but significant changes were detected in other variables that were not related to the virus inoculation process, such as the intracellular probe (pd) duration, which could suggest a possible effect of EF on the acquisition of CMV. Notably, a remarkable effect of B. bassiana endophytic colonization was found on CMV and CABYV transmission, with significant reductions of 21.9 and 24.4%, respectively, of the inoculation rates in B. bassiana-treated plants. These results suggest a possible systemic virus resistance in melon induced by fungal colonization.