Optimizing Irradiation Dose for Sterility Induction and Quality of <I>Bactrocera tryoni</I>

Abstract

The current study is an important step toward calibrating, validating, and improving irradiation methods used for Bactrocera tryoni (Froggatt) sterile insect technique (SIT). We used routine International Atomic Energy Agency/U.S. Department of Agriculture/Food and Agriculture Organization quality control tests assessing percentage of emergence, flight ability, sex ratio, mortality under stress, reproductive sterility, and sexual competitiveness, as well as a nonstandard test of longevity under nutritional stress to assess the impact of a range of target irradiation doses (60, 65, 70, 75, and 80 Gy) on the product quality of mass reared B. tryoni used in SIT. Sterility induction remained adequate (>99.5%) for sterile male-fertile female crosses, and 100% sterility was achieved in fertile male-sterile female crosses and sterile male-sterile female crosses for each irradiation doses tested. There was significant increase in mortality under stress as irradiation dose increased, and reduced participation in mating by males irradiated at higher doses. The current target-sterilizing dose for SIT of 70-75 Gy is associated with significant reduction in fly product "quality". Our data suggest that adequate sterility and improved fly quality could be achieved through a small reduction in target sterilizing dose.

Evaluating Irradiation Dose for Sterility Induction and Quality Control of Mass-Produced Fruit Fly <I>Bactrocera tryoni</I> (Diptera: Tephritidae)

“…In that study, all irradiation doses achieved adequate reproductive sterility (Ͼ99.5%), with the 60 Gy treatment providing mean sterility of 99.98%. Furthermore, this study found that longevity under crowding stress (FAOÐ IAEAÐUSDA 2003) correlated negatively with irradiation dose, and that sexual competitiveness steadily decreased with increasing irradiation dose (Collins et al 2009). These results strongly suggest that reduced irradiation dose would be beneÞcial to ßy quality and would not sacriÞce adequate sterility (see also Collins and Taylor 2011).…”

“…Performance of sterile ßies is dependent on a wide range of factors, including diet and production methods, irradiation dose, handling and transport stress, release methods, and Þeld conditions (Meats and Edgerton 2008, Campbell et al 2009, Collins et al 2009, Fanson et al 2009, Dominiak et al 2011a, Weldon and Taylor 2011. Consequently, SIT programs are continuously researching new methods to improve ßy quality and hence SIT success.…”

“…Recently, Collins et al (2009) evaluated a Þner range of irradiation doses (60 Ð 80 Gy in 5 Gy intervals) on quality control (QC) parameters. In that study, all irradiation doses achieved adequate reproductive sterility (Ͼ99.5%), with the 60 Gy treatment providing mean sterility of 99.98%.…”

“…However, there are two major constraints to implementation of recommendations arising from Collins et al (2009). First, as noted by Collins et al (2009), the buffer zone below the recommended 60 Gy target dose is unclear.…”

“…First, as noted by Collins et al (2009), the buffer zone below the recommended 60 Gy target dose is unclear. If ßies are accidentally under dosed, it is not clear if ßies would be adequately sterilized for SIT releases.…”