Inheritance of Diapause in Crosses between the Northernmost and the Southernmost Strains of the Asian Corn Borer Ostrinia furnacalis

The northernmost Harbin strain (N strain) of the Asian corn borer, Ostrinia furnacalis enters facultative diapause as fully grown larvae in response to short daylengths; whereas the southernmost Ledong strain (S strain) exhibits almost no diapause under the same light conditions. In the present study, we examined the inheritance of diapause induction and termination by crossing the two strains under a range of environmental conditions. The N strain showed a typical long-day response with a critical daylength of approximately15.88 h at 22°C, 15.72 h at 25°C and 15.14 h at 28°C, whereas the S strain showed a weak photoperiodic response at 22°C. The F1 progeny also showed a long-day response at 22, 25 and 28°C. However, the critical daylengths in S ♀ × N ♂ crosses were significantly longer than those in N ♀ × S ♂ crosses, indicating a sex linkage in the inheritance of diapause induction, with the male parent having more influence on the following F1 progeny. The incidence of diapause in S ♀ × N ♂ crosses was the same as in the N strain under short daylengths of 11-13 h, indicating that diapause trait is completely dominant over the non-diapause trait. The critical daylength in backcross to N was significantly longer than it was in backcross to S, showing a grandfather gene effect. Whether the inheritance of diapause fits an additive hypothesis or not was dependent on the rearing photoperiod, and the capacity for diapause was transmitted genetically in the manner of incomplete dominance. The duration of diapause for the reciprocal crosses under different diapause-terminating conditions showed different patterns of inheritance. The results in this study reveal that genetic and genetic-environmental interactions are involved in diapause induction and termination in O. furnacalis.