| Spodoptera frugiperda is a major migratory pest in the world and has a significant impact on world agricultural production.The strong migration ability and wide host range of S.frugiperda are important reasons for its difficulty in prevention and control.When encountering environmental stress,adults will migrate to an environment more suitable for the survival of offspring.Therefore,it is of great significance to study the feeding adaptability of S.frugiperda to host plants for its synthetical prevention and control.In this thesis,the growth and development indexes and detoxification enzyme activities of S.frugiperda larvae living on Zea mays,Triticum aestivum and Eleusin indica for a long time were observed.Based on transcriptome sequencing,the genes related to detoxification metabolism were screened for spatio-temporal expression profile analysis.Finally,the GSTs2 gene of S.frugiperda was RNAi,and the function of GST gene of S.frugiperda in host adaptability was further studied,in order to provide a theoretical reference for the synthetical prevention and control of S.frugiperda.The main results are as follows:1.Effects of three host plants on growth and enzyme activities of S.frugiperdaThe results of the study on the growth and development indexes of S.frugiperda larvae showed that there was a significant difference in the larval duration of F3 generation feeding on Z.mays,T.aestivum and E.indica(p < 0.05).The shortest duration(14.733 d)was fed on Z.mays,and the longest duration(16.700 d)was fed on E.indica.The larval duration of F3 generation fed on E.indica(16.700 d)was significantly longer than that of F1generation(15.267 d).The 10-day body weight(0.173 g and 0.177 g)and pupal weight(0.171 g and 0.193 g)of S.frugiperda larvae fed on Z.mays were significantly higher than those fed on wheat and E.indica.The pupal weight(0.193 g,0.138 g and 0.170 g)of F3 generation fed on Z.mays,T.aestivum and E.indica were significantly higher than that of F1 generation(0.171 g,0.108 g and 0.120 g).The results of detoxification enzyme activity of S.frugiperda larvae showed that the activities of GST(18.001 U/mg prot),Car E(20.089 U/g)and P450(1.382 ng/m L)in F1 generation fed on E.indica were significantly higher than those fed on Z.mays(13.511U/mg prot,10.667 U/g and 1.382 ng/m L)and T.aestivum(14.919 U/mg prot,17.067 U/g and 1.508 ng/m L).The activities of GST(15.977 U/mg prot)and Car E(15.918 U/g)in F3 generation were significantly higher than those in Z.mays(12.956 U/mg prot and 10.453U/g)and T.aestivum(14.035 U/mg and 12.800 U/g).The GST and Car E activities of F3 generation feeding on T.aestivum and E.indica were significantly lower than those of F1 generation.2.Transcriptome sequencing analysis of S.frugiperda and screening and identification of detoxification metabolic genesThe midgut of S.frugiperda larvae fed on three hosts was sequenced by transcriptome,and the midgut transcriptome of larvae fed on Z.mays was used as a control.The results showed that a total of 1917 genes were annotated by KEGG.Among them,215 differentially expressed genes were co-annotated in T.aestivum and 119 differentially expressed genes were co-annotated in E.indica.Compared with the control,there were 462 and 337 significantly differentially expressed genes in T.aestivum and E.indica,respectively.There were 100 differentially expressed genes in both,and there were 3 differentially expressed genes related to detoxification metabolism(Sf GSTs2,Sf ACh E1 and Sf ESTFE4).3.Spatial and temporal expression profile analysis of detoxification metabolic genes in S.frugiperdaThe temporal and spatial expression profiles of three detoxification metabolic genes screened by transcriptome were analyzed.The results showed that the expression levels of the three genes were different at different developmental stages(p < 0.05).The expression levels were lower in 1-2 years old and higher after 3 years old.Comparison of different tissues showed that the three genes were highly expressed in the midgut.Compared with different hosts,it was found that the expression levels of the three genes were higher on Z.mays at young age,lower on T.aestivum and E.indica,and opposite after 3 years old.4.Functional analysis of GSTs2 gene in S.frugiperdaThe RNAi results of Sf GSTs2 gene showed that compared with dse GFP,the expression of Sf GSTs2 gene was significantly down-regulated by 75.1 %,45.0 % and 47.4 % after 24 h of RNAi in S.frugiperda fed on Z.mays,T.aestivum and E.indica,respectively.The results of weight detection of S.frugiperda after Sf GSTs2 gene interference showed that compared with dse GFP,the weight of S.frugiperda ds GSTs2 feeding on three host plants decreased significantly at 24 h,48 h and 72 h(p < 0.05);the weight of S.frugiperda ds GSTs2 fed on Z.mays decreased by 58.3 %,67.6 % and 57.6 %,respectively;the weight of S.frugiperda ds GSTs2 fed on T.aestivum decreased by 51.6 %,27.3 % and 37.7 %,respectively.The weight of S.frugiperda ds GSTs2 fed on E.indica decreased by 22.3 %,33.3 % and 28.6 %,respectively.Compared with dse GFP,the mortality rate of S.frugiperda ds GSTs2 fed on three host plants was significantly increased at 72 h,but there were differences in the three hosts(p < 0.05).The specific performance was Z.mays(34.5 %)> E.indica(26.9 %)>T.aestivum(16.7 %).The results of GST activity after interference with Sf GSTs2 gene showed that compared with dse GFP,the activity of ds GSTs2 in S.frugiperda feeding on Z.mays,T.aestivum and E.indica decreased significantly(p < 0.05),which were 8.0 %,22.3 %and 6.8 %,respectively. |
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