Inherited Sterility in Progeny of Irradiated Male Tobacco Budworms1: Effects on Reproduction, Developmental Time, and Sex Ratio

Abstract

When male Heliothis virescens (F.) were irradiated with 15 or 22.5 kr of gamma irradiation, the F₁ progeny were nearly sterile, and the F₁ male progeny did not mate or transfer sperm as well as normal males. When the dose to the P₁ male was 15 kr, about 1/3 of its male progeny did not mate, and only about 1/2 those that mated transferred sperm; with increased dose, this inability to mate increased. The percentage of the F₁ female progeny that mated was nearly as high as the percentage of normal females, but fecundity was markedly reduced when the P₁ male was irradiated with 15.0 or 22.5 kr. Also, the F₁ progeny had a delayed developmental time, increased larval and pupal mortality, and a distorted sex ratio (about 2 males/female). The application of inherited sterility has several advantages in controlling field populations. The main benefit results from the usc of P₁ males with less irradiation- induced damage. The data indicate that the dose of radiation given to the P₁ males might be lowered to 15 krad. Such males would be more competitive with native males; thus, by overflooding a field population, one would reduce the population density and alter the population structure to one made up largely of sterile individuals. Then continued releases of such males might achieve eradication.