Mass-rearing and field cage performance of a transgenic sexing strain ofMediterranean fruit fly.” .

NI MORRISON; DF SEGURA; V WORNOAYPORN; A ISLAM; KC STAITON; C CACERES; G FRANZ,; L ALPHEY; AS ROBINSON

Palma de Mallorca

Congreso; First Meeting of TEAM.; 2008

A strain of Mediterranean fruit fly, OX3376B, carrying a female-lethal transgene insertion has been reared in mass-rearing conditions. The lethal effect of the transgene insertion is repressed in the presence of tetracycline or related compounds. The strain is homozygous for the insertion and marked with a green fluorescent protein. Characteristics of the strain related to rearing productivity were assessed, as well as stability of the transgene and its properties. With chlortetracycline hydrochloride (>70 g/kg) in both larval diet and adult diet and drinking water, fecundity of the OX3376B strain (150 eggs/female, s.d. 9) is at least comparable with the conventional sexing strain (temperature sensitive lethal), Vienna-8 (121 eggs/female, s.d. 16). Egg hatch rate of OX3376B is also comparable with that of Vienna-8, although this drops after 5-7 days, possibly as a result of a lack of CTC available to the adult flies. Rearing of OX3376B larvae on CTC results in eclosion rates (>90%) comparable with those of the Vienna-8 strain, although the percentage of emerging females is lower than that of males. Monitoring of each generation of OX3376B pupae was carried out for presence of the green fluorescent marker. No non-fluorescent pupae were detected. In addition, from larvae reared in the absence of CTC in each generation, no female adults were found from large collections of pupae. Comparison of the mating competitiveness of OX3376B males with those from a wild-type laboratory strain was carried out in field cage conditions. Overall, OX3376B achieved a relative sterility index of 0.37. In summary these data indicate that, despite limitations associated with this specific transgene insertion, the use of a transgenic sexing strain may provide a viable alternative to conventional sexing strains of Mediterranean fruit fly for SIT-type control programmes in the future.