Effect of gamma radiation on biological parameters and male sterility in Melon fruit fly, Zeugodacus cucurbitae (Coquillet)

Larvae of melon fruit fly, Zeugodacus cucurbitae were reared on artificial liquid larval diet to produce the enough pupae required for radiation sterilization. Seven days old male pupae of Z. cucurbitae were exposed to eight different doses of gamma radiation (Cobalt 60 source) to identify the optimum dose of gamma radiation. Among eight doses, 50 Gy had induced 80.26% of sterility with least negative effects on quality parameters such as adult emergence, adult flying ability, deformation, adult longevity and survival under food stress. Although more than 90% of sterility was obtained at 70, 90 and 100 Gy but quality parameters of sterile males were drastically affected. Hence the radiation dose 50 Gy was selected for studying the mating competitiveness of sterile males (SM) with normal males (NM) for their normal females (NF) at seven different sex ratios of 1:1:1, 2:1:1, 3:1:1, 4:1:1, 5:1:1, 7:1:1 and 9:1:1 (SM:NM:NF, respectively) in laboratory cages. Observed and expected egg hatches were worked out for each mating sex ratio using Fried equation. Sterile males were equally competitive with normal males for their female mates at 5:1:1 with competitiveness value (CV) of 1.02. Sterile males showed superior competitiveness with normal males for their female mates at 7:1:1 (CV = 1.60) and 9:1:1 (CV = 1.98).