| This research aimed at studying the effects of different radiation doses on development and reproduction of Bactrocera dorsalis (Hendel) at different egg-stages, trying to find a suitable radiation dose and radiation egg-stage of B. dorsalis for mass rearing of parasitoids. And irradiated hosts were used to raise Fopius arisanus (Sonan).1. The dose rate (1Gy/min) this paper used was derived from previous studies. To study the influences of different radiation doses on development and reproduction of B. dorsalis at different egg-stages, three different ages of B. dorsalis eggs (12-,24-and 36-h-old) were analyzed for egg hatchability, pupae weight, emergence ability, sex-ratio, flight capacity, mortality rate and fertility after being subjected to radiation doses of 5,10,15,20,25,30,35 and 40Gy. The results showed that the egg hatching rate of 36-h-old and 24-h-old eggs irradiated below 20Gy were not statistically different from the control group (non-irradiated egg). And the egg hatching rate of 12-h-old and 24-h-old eggs irradiated above 15Gy were statistically different from the control group. The clear descrease in pupae weight of B. dorsalis progressed as the radiation dose beyond 20Gy. And no adult emergence occurred at radiation doses greater than 20Gy. With the radiation dose increasing adult emergence rate, fly ability, the number of emergence adult and egg hatch rate of F1 decreased but the number of deformed adult, dead pupae, unsuccessful emergence adult and mortality rate increased. It was proved that there were not clear difference in the sex-ratio in all groups and radiation had the same effects to the female and male of B. dorsalis.2. The significant reduction in egg hatching rate and pupae rate occurred with 24-h-old and 27-h-old eggs at any of the radiation dose levels. The clear lessening in pupae weight occurred at radiation doses greater than 20Gy at any of the radiation egg-stages.24-h-old and 27-h-old eggs irradiated at any radiation doses and any egg-stages irradiated above 20Gy were found to not be the suitable age and dose for fruit fly egg hosts to be used in mass rearing the parasitoid. The emergence percentage, fly ability and F1 egg hatching percentage of 30-h-old,33-h-old,36-h-old eggs irradiated at 15Gy were much higher than the same egg-stages irradiated at 20Gy.Moreover the adult mortality rate of 30-36-h-old eggs irradiated at 15Gy was much lower than the same egg-stages irradiated at 20Gy.And pupae weight and pupae percentage of both two doses was not significant different from the control group. It was demonstrated that 30-36-h-old eggs irradiated at 20Gy were found to be the best ages and dose for fruit fly egg hosts to be used in mass rearing the egg parasitoid F. arisanus.3. The 30-36-h-old eggs of B. dorsalis irradiated at 20Gy were used as hosts for Fopius arisanus (Sonan),the parasitoids emerge, flies did not emerge. Parasitic rate, parasitoids emergence percentage, sex-ratio (female:male) and longevity were tested indoor from F1 to F3. The results showed that there was no significant difference in parasitic rate and emergence percentage, but notable difference in sex-ratio (female:male) and longevity. But the differences soon eliminated in F2 and F3. It were Indicated that the offspring parasitoids were better than the parasitoids emerge from the irradiated hosts directly.4. The parasitic percentage, parasitoids emergence rate, sex-ratio (female:male) and longevity of parasitoids reared with irradiated hosts were similar to the parasitoids obtained from non-irradiated host eggs in outdoor experiment. It made clear thatFopius arisanus (Sonan) reared with irradiated hosts also could search and parasitic host indoor and outdoor normally, the parasitoids could develop in the host body regularly. The fruit-fly parasitoids reared with irradiated eggs could be release in the field directly. |
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