Pea protease inhibitor inhibits protease activity and development of Bactrocera cucurbitae

Abstract

Melon fruit fly, Bactrocera cucurbitae (Coquillett) is an important pest of cucurbit crops that can cause severe damage to its host species and thus drastically reduce the crop production. In recent years, protease inhibitors have been extensively explored against lepidopteran and some coleopteran insects and have shown significant inhibitory effects against them. They are therefore increasingly being explored for enhancing resistance in crops to insect pests. In the present study, bioassays conducted with pea protease inhibitors showed significant adverse effect on the development and physiology of the larvae of melon fruit fly. The incorporation of different concentrations (12.5, 25, 50, 100, 200 and 400μg/mL) of the pea protease inhibitor into the artificial diet of second instar (64–72h old) larvae, had significant inhibitory effects (p<0.01) when monitored through bioassays for various growth parameters such as larval period, total development period, pupal weight, percentage pupation and percentage emergence as compared to control. Enzymatic assays at different concentrations (50, 100, 200 and 400μg/mL) of pea protease inhibitor (PI) significantly reduced the activities of digestive enzymes (trypsin, chymotrypsin, leucine aminopeptidase and elastase) with an increase in treatment interval.