Inherited sterility in progeny of gamma irradiated male cotton leafworm, Spodoptera littoralis (Boisd.)

The fecundity, egg hatch and mating of normal females of Spodoptera littoralis (Boisd.) crossed with males irradiated as 7-day-old pupae with doses of 50, 75, 100, 125, 150 and 200 Gy of gamma radiation were studied. The inherited effects of irradiation were studied until the F3 generation. Also, the progeny of males treated with 100 Gy were outbred or inbred with untreated individuals for two successive generations and the progeny were observed for any inherited deleterious effects on reproduction. The fecundity of females was significantly reduced by increasing the dosage applied to P1 males. The egg hatch of P1 females was significantly reduced at 125, 150 and 200 Gy treatments as compared with the untreated control. The F1 generation was significantly more sterile than the irradiated parents. The irradiation of P1 males did not affect their mating, sperm transfer or mating frequency nor were these impaired in the successive generations of the different crosses. However, a detectable reduction in the percentage of mated females with sperm and a significant increase in number of spermatophores per mated female were observed among the F1 generation at a dose level of 200 Gy. The larval and pupal mortality in the F1 and F2 generations were high and dose dependent. The average developmental time from egg hatch to adult emergence was not affected and also the sex ratio of resulting progeny was about normal. Males irradiated with 100 Gy of gamma radiation and released into field cages caused significant reductions in the populations. The population of the cages containing partially sterile males was reduced by about 43% in comparison with control cages. Laboratory mating competitiveness indicated that males irradiated with 100 or 150 Gy and their F1 sons were fully competitive against untreated males in mating with untreated females. (author). 13 refs, 1 fig., 8 tabs