Inheritance of photoperiodic induction of larval diapause in the Asian corn borer Ostrinia furnacalis

The Asian corn borer Ostrinia furnacalis (Guenee) enters facultative diapause as fully-developed larvae in response to short-day conditions. As a consequence of geographical variation in photoperiodic response, moths from Nanchang (28 degrees 46'N, 115 degrees 50'E) enter diapause in response to short day-lengths (D strain), even at the high temperatures whereas moths from Ledong (18 degrees 47'N, 108 degrees 89'E) exhibit almost no diapause under the same conditions (N strain). In the present study, crosses between the two strains are used to evaluate the inheritance of diapause under different photoperiods at temperatures of 22, 25 and 28 degrees C. The moths, both reciprocal crosses and backcrosses, show a clear long-day response, similar to that of the D strain, suggesting that the photoperiodic response controlling diapause in this moth is heritable. However, the critical day-length for induction of diapause is shorter in hybrids than in the D strain. The N strain also shows a short-day photoperiodic response at the lower temperature of 22 degrees C, indicating that the N strain still has the capacity to enter a photoperiodically-induced diapause, depending on the rearing temperature. The incidence of diapause in all crosses is highest with D strain fathers or grandfathers and lowest with N strain fathers or grandfathers, indicating that the male parent has significantly more influence on the incidence of diapause of subsequent progeny than the female. The results obtained from all crosses under LD 12 : 12 h or LD 13 : 11 h photocycles at 25 degrees C show that inheritance of diapause in O. furnacalis does not fit an additive hypothesis and that the capacity for diapause is transmitted genetically in the manner of incomplete dominance.