Studies On The Diapause And Cold Tolerance Of The Overwintering Egg Of Apolygus Lucorum

The thesis studied the effects of temperature and photoperiod on diapause termination and diapause induction of the egg of Apolygus lucorum Meyer-Dür. The thesis also studied the cold tolerance of overwintering egg of A. lucorum and analysed the relation with biochemical substances in the body. Primary diapause mechanism of the egg of Apolygus lucorum and the relation with month was proved. The results are shows:To understand the effects of temperature and photoperiod on diapause termination and post-diapause development of the overwintering egg of A. lucorum , the hatch rate and hatch time of the overwintering egg of A. lucorum at different temperature and different photoperiod were systematically investigated. The results showed that the overwintering eggs of A. lucorum are all diapause eggs, and their diapause termination could be influenced by low temperature and photoperiod. Low temperature (2℃) affected the diapause termination. The time of diapause termination was shortened with the increment of treatment time of low temperature in the 0 to 65 d treatments, and the T50 values of that without low temperature treatment and the treatment for 65 d by low temperature was 68.5 d and 12.5 d, respectively. The diapause termination of overwintering eggs was completed after 65 d of low temperature treatment. The hatch rate of the overwintering eggs increased with the treatment time of low temperature in the 0 to 40 d treatment. The hatch rate of overwintering eggs without low temperature treatment was 68.65% at 25℃and full light, and 99.46% with low temperature treatment 40 d. The developmental duration of post-diapause reduced with the increasing of temperature and photoperiod in 20℃~26℃. The results suggest that low temperature could increase the diapause termination rate of overwintering eggs but is not the necessary condition for diapause termination. Effects of low temperature and nature temperature to the diapause termination were similar. High temperature and long photoperiod may promote the diapause termination of overwintering eggs and reduce their developmental duration.To understand the effects of temperature and photoperiod on egg diapause induction of Apolygus lucorum Meyer-Dür, the hatch rate and hatch time of A. lucorum egg laid by those rearing at different temperature and different photoperiod were systematically investigated. The first instar larvae of A. lucorum is the sensitive stage. Daylength less than 14 h were benefit to diapause induction, and daylength more than 14 h were benefit to growth and diapause inhabitation at three different temperature (17℃,20℃,23℃). Short daylength had a cumulative effect on diapause induction. The diapause rate decreased with the increment of temperature in the daylength from 10h to 14 h, and temperature had no effect on diapause induction in the daylength more than 14 h. The critical photoperiod of A. lucorum was L13h10min:D10h50min,L12h58min:D11h2min and L12h51min:D11h9min at 17℃,20℃and 23℃,respectively. The critical daylength shortened with the increment of temperature. The results showed that A. lucorum was a typical long-day insect. Photoperiod was the main factor of diapause induction. Temperature was the cofactor of diapause induction, and low temperature at autumn was benefit to the diapause induction.In this study, cold tolerance of overwintering egg were investigated and the relation with biochemical substances in the body were analysed. The results indicated that cold survival ability of the overwintering eggs was significantly different among the months.The overwintering eggs in January or February had higher tolerance to low temperature than the other months. The mortality of protected eggs in the April (4.32%,5.36%,5.42%,6.79% and 7.63%) was significantly low than non-protected eggs in the April (46.06%,51.84%,54.59%,63.07% and 74.41%) when they were treated 1,2,3,4 and 5 days at the temperature of -20℃. The aitificial diapause eggs had higher tolerance to low temperature than the normal eggs,and had lower tolerance to low temperature than the overwintering eggs . Overwintering eggs undergo a process of cold acclimation that can increase their cold tolerance before the occurrence of low temperatures. The water content of overwintering eggs increased or reduced with temperature reducing or increasing. The fat content of overwintering eggs decreased with the time in winter. The protein content and glycogen content reduced at first, then increased.