Geographical variation and inheritance of the photoperiodic response controlling larval diapause in two distinct voltine ecotypes of the Asian cornborer Ostrinia furnacalis

The Asian corn borer Ostrinia furnacalis Guenee (Lepidoptera: Crambidae) enters facultative diapause as fully-grown larvae in response to short day lengths during autumn. As a result of geographical variations in photoperiodic response, the moths from Nanchang (28.8 degrees N, 115.9 degrees E; NC strain) judge both LD 14:10h and LD 15:9h photocycles as long days and develop directly, whereas moths from Haerbin (44.9 degrees N, 127.2 degrees E; HB strain) judge the same photocycles as short days and enter diapause. Crosses between the two strains are used to evaluate the inheritance of diapause. The critical day lengths for diapause induction in the HB strain are significantly longer than those in the NC strain at all temperatures. The critical day length of F1 progeny is intermediate between the two strains. However, the critical day length in all crosses is significantly longer with HB strain fathers or grandfathers than with NC strain fathers or grandfathers, indicating that the male parent has significantly more influence on the critical day length of subsequent progeny than the female. The results from all crosses under LD 14:10h or LD 15:9h photocycles at 25 degrees C show that the inheritance of diapause in O. furnacalis does not fit a purely additive hypothesis and that the capacity for diapause is transmitted genetically in the manner of incomplete dominance. The incidence of diapause for F1 progeny under an LD 14:10h photocycle is significantly higher than that under an LD 15:9h photocycle, suggesting that the induction of diapause can be influenced by interactions between the F1 genotype and photoperiod.