Development of a Pupal Color-Based Genetic Sexing Strain of the Melon Fly, Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae)

Abstract

The first genetic sexing system for the melon fly, Bactrocera cucurbitae (Coquillett), based on pupal color was developed. The recessive white pupae mutant, wh, was used in a putative chromosome translocation linking the wildtype allele to the male sex. This system permits the separation of males (wildtype brown pupae) from females (mutant white pupae). Results from laboratory studies indicated that egg hatch averaged 42% for flies 2–5 wk old, with higher rates (≈50%) for younger flies in this age range. Male larvae left the diet to pupate earlier than females, averaging >60% of the pupae in the first day of collection, whereas only ≈40% on the fourth day of collection. Adult emergence rate was normal, averaging ≈92%. Adult egg fecundity and fertility (both sexes) were very low (80%) as wild males over a 7-d period when provided with food and water. Mating tests indicated that male-only sterile flies mated significantly more (about double) with wild females than sterile males from bisexual (male and female) sterile populations competing with wild males. Males fed only sugar until tested in the cages failed to mate with wild females, whereas males fed a low protein diet (6:1 sugar:protein) or the standard 3:1 diet mated as well as wild males for wild females. Finally, males exposed to the attractant, cuelure, failed to improve their mating performance compared with control, unexposed males. The results are discussed in the context of the potential for using the new strain in current or future melon fly sterile insect technique programs in Hawaii and elsewhere.