Optimization Of Diapause Conditions And Effect Of Diapause On Heat Shock Protein Genes Of Trichogramma Japonicum

Rice Lepidopteran pests,which cause serious damage,are the main pests during rice producing in China.Biological control of Lepidopteran pests by Trichogramma japonicum,which is the dominant egg parasitic wasp of rice Lepidopteran pests,has the characteristics of safety,environmental protection and sustainability,and it can reduce the use of chemical insecticides.How to breed Trichogramma with large quantity and produce high-quality Trichogramma has already been a research hotspot of biological control workers,however,as a natural enemy commodity,Trichogramma has some technical defects,such as short shelf life,which ultimately leads to cost high pressure and high production for T.japonicum in the short term.In order to solve this technical bottleneck,the widely accepted method is to use the characteristics of insect diapause to improve the storage time of Trichogramma.At present,some of diapause conditions and diapause mechanism about Trichogramma have been reported,but there are few studies on diapause conditions and diapause mechanism about T.japonicum.In this paper,the diapause and storage conditions of T.japonicum were optimized,and the biological characteristics of the diapause T.japonicum were evaluated.At the same time,the effects of diapause on the expression of heat shock protein gene were explored to provide a theoretical basis for prolonging the shelf life of T.japonicum.The main results are as follows: 1.Optimization of the diapause conditions on T.japonicumThe population of short daylength(8L:16D)condition was more likely to enter diapause state;the most sensitive inducing initial stages were 12 or 24 h,and the diapause effect decreased with the growth of the insect age;the induced temperature also have a significant effect on diapause,the diapause rate of the short-daylength population at the inducing temperature of 13? is significantly higher than that of 10?,but the diapause rate of the other two photoperiod populations at the inducing temperature of 10? was significantly higher than that of 13?;the diapause rate of T.japonicum was also increased significantly with the extension of induction period.The storage temperatures have a significant effect on the emergence rate of diapause T.japonicum,the emergence rate of 4 ? is significantly higher than the other three temperatures;storage times also have a significant effect on the emergence rate of diapause T.japonicum,the emergence rate of diapause T.japonicum increased and then decreased with the extension of storage time.The emergence rate of diapause T.japonicum in short-daylength(8L:16D)condition is significantly higher than other two photoperiods;the inducing temperatures have a significant effect on the emergence rate of diapause T.japonicum,the emergence rate of the long-daylength population at the inducing temperature of 10? is significantly higher than that of 13?,and the other two is on the contrary;The emergence rate of different populations of T.japonicum at the inducing initial stage of 24 h is significantly higher than that of 48 h;the induction periods and storage times also have significant effects on emergence rate,the emergence rate is higher with the extension of the induction period,and the emergence rate of inducing period of 35 d is significantly higher than other induction times,and the emergence rate of storage time of 60 d was significantly higher than other storage times.The optimal diapause conditions and storage conditions according to the test conditions are that the short-daylength population is induced at 13? for 35 d at the inducing initial stage of 24 h and stored at 4? for 60?90 d.2.Biological evaluation of diapause T.japonicumThere was no significant difference in the parasitic ability of diapause T.japonicum with different diapause types and storage time;different diapause types and storage time have significant effects on the emergence ability of diapause T.japonicum;the emergence ability of the diapause type which was the population of 8L:16D,inducing initial stage of 24 h,experienced at 13? for 35 d is significantly stronger than that of other diapause types;different diapause types and storage times have significant effects on the spread ability of diapause T.japonicum,the spread of diapause T.japonicum was significantly higher than that of non-diapause T.japonicum,and the spread ability of diapause T.japonicum of 16L:8D was significantly lower than that of other diapause bees;different diapause types,storage times and emergence times have significant effects on the emergence stage of diapause T.japonicum.Comparing with non-diapause T.japonicum,the emergence stage of diapause T.japonicum was extended 1 d than that of diapause T.japonicum,there was no significant difference between 1 d and 2 d about emergence ratio of diapause T.japonicum,but they were significantly higher than that of 3 d.3.Effect of diapause on gene expression of heat shock proteinThe expression characteristics of 14 heat shock protein genes TjHsp10,TjHsp60,TjHsp68,TjHsc70-3-X1,TjHsc70-3-X2,TjHsc70-4-1,TjHsc70-4-2,TjHsc70-4-2,TjHsc70-5,TjHsc70-5,TjHsp75,TjHsp90,TjHsp97,TjHsfp-1 and TjHsfp-2 combined with the result of diapause rate showed that 8 genes might be related to diapause.TjHsp10,TjHsc70-3-X2,TjHsc70-4-3,TjHsc75,TjHsp90 and TjHsfp-1 were all significantly up-regulated in the early diapause period,and the expression levels decreased gradually with the extension of diapause induction periods,which may take part in the diapause induction process.The expression levels of TjHsc70-5 and TjHsfp-2 increased gradually with the extension of diapause induction time,which may take part in the maintenance of diapause.