Studies On Inheritance Of Diapause And Life-history Traits Of Asian Corn Borer Ostrinia Furnacalis (Guenée)

The Asia corn borer, Ostrinia furnacalis (Guenée)(Lepidoptera, Crambidae), isserious pest in corn. O. furnacalis enters diapause as fully-developed larvae in response toshort-day conditions, and is widely distributed in China due to its adaptation to diverseenvironmental conditions. Life-history diversity exists among different geographicalpopulations as a result of different environmental conditions the O. furnacalis encounter,including difference of voltinism, critical photoperiod, and emergence time after diapausetermination, and cold tolerance.In this thesis, we investigated the diapause inheritance by crossing two differentgeographical populations of O. furnacalis, the effects of photoperiod and temperature onboth diapause termination and growth and development of individuals. The results are asfollows.1. Inheritance of the photoperiodic larval diapause induction of the Asian cornborerThe Asian corn borer Ostrinia furnacalis (Guen′ee) enters facultative diapause asfully-developed larvae in response to short-day conditions. As a consequence ofgeographical variation in photoperiodic response, moths from Nanchang(28°46′N,115°50′E) enter diapause in response to short day-lengths (D strain), even at the hightemperatures whereas moths from Sanya (18°47′N,108°89′E) exhibit almost nodiapause under the same conditions (N strain). In the present study, crosses between thetwo strains are used to evaluate the inheritance of diapause under different photoperiods attemperatures of22,25and28C. The moths, both reciprocal crosses and backcrosses,show a clear long-day response, similar to that of the D strain, suggesting that thephotoperiodic response controlling diapause in this moth is heritable. However, the criticalday-length for induction of diapause is shorter in hybrids than in the D strain. The N strainalso shows a short-day photoperiodic response at the lower temperature of22C,indicating that the N strain still has the capacity to enter a photoperiodically-induceddiapause, depending on the rearing temperature. The incidence of diapause in all crosses ishighest with D strain fathers or grandfathers and lowest with N strain fathers orgrandfathers, indicating that the male parent has significantly more influence on theincidence of diapause of subsequent progeny than the female. The results obtained from allcrosses under LD12:12h or LD13:11h photocycles at25C show that inheritance ofdiapause in O. furnacalis does not fit an additive hypothesis and that the capacity fordiapause is transmitted genetically in the manner of incomplete dominance.2. Effect of photoperiod and temperature on the intensity of larval diapause in the Asian corn borerEffects of temperature and photoperiod on the intensity of larval diapause in the Asiancorn borer, O. furnacalis from Nanchang and Sanya were investigated as well as theirhybrid offspring. By transferring diapausing pupae induced under photoperiods of LD11:13, LD12:12and LD13:11at22°C,25°C and28°C, to LD15:9with the each rearingtemperature, the diapause duration decreased with increasing daylength at all temperatures.The diapause individuals induced under LD11:13and LD12:12at22°C from Sanyashowed significantly shorter diapause durations, compared with diapause individuals fromNanchang. Diapause duration in hybrid larvae was intermediate between those of theirparents, suggesting that diapause duration is under the control of polygene. When theoverwintering larvae of Nanchang population were transferred at different times fromnatural condition to25°C with LD12:12and LD15:9, it was found that, the earlier thetransfer took place, the earlier the larvae pupated when the time spent under naturalconditions was included.3. Effect of temperature and photoperiod on development of the Asian cornborerThe southern-most Sanya population of O. furnacalis shows a much low diapauseeven when they were reared under the short photoperiod of LD11:13at the lowtemperature of18°C. Therefore, the effect of temperature and photoperiod on life historytraits of the Asian corn borer, O. furnacalis was investigated in laboratory at18,20,22,25,28and31°C combined with LD11:13and15:9, respectively. Just as the life history theorypredicts, the development time decreased, while growth rate increased at highertemperatures and maybe still below the physiological upper limit, whereas pupal weightincreased at higher temperatures was in contrary to life history theory, which is rarelydiscovered in insects. The life history traits were less plastic in response to photoperiodcompared to temperature. However photoperiod had still significant influence ondevelopment time. The pronounced protandry was only appeared at18and20°C, the pupalweight of female was larger than that of male(female biased sexual size dimorphism, SSD),suggesting that the both protandry and SSD were influenced by temperature.