Effect of the size of the founder population on the quality of sexual populations of Trichogramma pretiosum, in laboratory

The goal of this research was to monitor the quality of three sexual populations of the parasitoid wasp Trichogramma pretiosum Riley initiated with different numbers of founders in order to determine the ideal number to start mass rearing of this species. The parasitoids were collected in a corn field, on eggs of Helicoverpa zea (Boddie), and kept in the laboratory on eggs of the factitious host Anagasta kuehniella (Zeller). Virgin males and females, collected in different sites, were selected and used in controlled crossings to start the laboratory populations. Rearing units initiated with one, five, or 10 founder couples were set up, each with five replications. The populations were kept in a system of consanguineous crossings during 25 generations, monitoring at each generation, the effective number of individuals and the coefficient of inbreeding. The populations were submitted to quality evaluations, also based on biological variables, monitoring the number of parasitized eggs, emergence rate, sex ratio, longevity, and percentage of deformed adults. It was concluded that it is possible to start T. pretiosum cultures, from a single couple, without significant alterations in biological features, making the maintenance of a good quality laboratory population possible for at least 25 generations. The results indicated that inbreeding is not a limiting factor for mass rearing of T pretiosum. (C) 2004 Elsevier Inc. All rights reserved.