Inherited Sterility in Progeny of Irradiated Male Cabbage Loopers1

Abstract

When normal female cabbage loopers, Trichoplusia ni (Hubner), were mated with adult males that had received 20 krad of gamma radiation, 15-20% of their eggs hatched. The progeny of this cross were sterile when they mated with normal moths of the opposite sex. Thus, the F1 progeny are more sterile than their irradiated male parents. Irradiation of the parental and F1 generations with 10 krad each did not cause more or less sterility in the F1 generation than 20 krad of irradiation to the P1 generation. Apparently the inherited sterility in the F1 generation is caused by the induction of large numbers of reciprocal chromosome trans locations. The abnormally high frequency of induced trans locations was probably the result of a unique chromosomal structural feature of Lepidoptera; namely, diffuse centromeres. The complete sterility obtained in the F1 generation when only a substerilizing dose of radiation was given to the male parent may prove of added value in using the sterile-male technique for eradication of Lepidoptera. Reducing the amount of radiation administered to an individual to effect sterility could well improve the competitiveness of the sterile male, a limiting factor thus far in the sterile-male release of Lepidoptera.