The roles of entomopathogenic fungal infection of viruliferous whiteflies in controlling tomato yellow leaf curl virus

Abstract

Efforts to control plant viral diseases have mainly focused on chemical control of their vectors and the development of plant resistance. However, the development of pesticide resistance in many vectors has meant that other vector control options such as the utilization of entomopathogens are receiving increasing attention. Entomopathogens may have the added benefit of suppressing viruses in vectors as well as killing the vectors, although this effect needs further testing under field conditions. Here, we pursue this idea by focusing on the entomopathogenic fungusIsaria javanica, isolated from Q type Bemisia tabaci (whitefly), which is considered the main vector of Tomato yellow leaf curl virus (TYLCV). We also provide insights into potential mechanisms involved in fungus-virus interactions.When nymphs and adults of viruliferous Q whiteflies were infected by I. javanica, there was a significant decrease in the amount of virus they carried. Isaria javanica fermentation (at 2 × 106 spores/mL) caused degradation of the CP capsid protein of TYLCV, with the supernatant from the fermentation showing higher degradation activity than the precipitate. The fungal infection was associated with an increase in plant height and a decrease in the disease index of tomato plants attacked by viruliferous Q type whiteflies. These findings indicate that entomopathogenic I. javanica fungi isolated from Q type whiteflies not only play an insecticidal role but also act as a plant virus suppressor that decreases the amount of TYLCV in the insect vector.