Isolation and Characterization of Bacterial Gut Symbionts from Irradiated, Wild and Lab Reared Males of Melon Fly, Zeugodacus cucurbitae (Coquillett)

Abstract

The melon fly, Bactrocera cucurbitae is of serious concern inflicting heavy losses to the horticultural industry. It attacks cucurbits right from the primordial stages of the crop up to harvest and causing yield loss of 30 to 100%. The Sterile Insect Technique is a species-specific and environmentally non-polluting method of insect control that relies on sterilization of males using gamma rays and systemic release of sterile males in wild environment. Male pupae of Zeugodacus cucurbitae were exposed to gamma radiation at 50 Gy using Cobalt-60 source. Bacterial gut symbionts from sterile males, wild males of field collected population and laboratory reared males of melon fly were isolated and characterized based on morphological characteristics (viz., colour, size, shape, opacity, margin, elevation and viscosity), gram staining, morphology and arrangement of bacterial cells in culture media. Ten adult flies from sterile, wild and laboratory reared males were used for isolation of gut symbionts. The most dominant phylum of bacteria found among the sterile, wild and lab reared male flies was Proteobacteria followed by the phylum Firmicutes. Different genera of bacteria isolated from sterile males were Enterobacter, Providencia and Bacillus. From wild males; Enterobacter, Providencia, Morganella, Klebsiella and Bacillus were identified. Bacterial genera obtained from lab reared males were Enterobacter, Providencia, Klebsiella and Bacillus. Among the entire bacterial genus, Enterobacter, Providencia and Bacillus were the common bacterial genera isolated from sterile, wild and lab reared male flies. Irradiation had resulted in loss of endosymbiotic bacteria in sterile males.