Molecular Toxicological Mechanism Of Competition Between Cydia Pomonella And Graphtha Molesta

The codling moth Cydia pomonella is an invasive pest and the oriental fruit moth Grapholitha molesta is a native pest of the pear,both of which belong to the Lepidoptera,Tortricidae.According to ecological theory,two species with high niche overlap and niche similarity will inevitably compete.However,there are few reports about the niche and interspecific relationships of the two similar insects.In insects,cytochrome P450monooxygenase（P450 or CYP）is mainly involved in the detoxification metabolism of exogenous toxin,such as plant secondary allelochemicals.Therefore,analyzing the differences in the adaptability and metabolic capacity of two pests to plant secondary allelochemicals from the perspective of molecular toxicology will help reveal the mechanism of interspecific competition between two pests and the invasion and spread mechanism of C.pomonella.Here,we explore the resource utilization of the two pests and the competition between species by studying the niche width,niche overlap,and niche similarity of C.pomonella and G.molesta,in the sequence of time and space resources;Determination of the effects of two main plant secondary allelochemicals coumarin and quercetin on two pests;Systematic identification of P450s genes in transcriptome of C.pomonella,and the expansion and contraction of their gene family members,and analyze the molecular response of P450s genes to plant secondary allelochemicals.The main research results of are as follows:1)The niche of C.pomonella and G.molesta and their interspecific competitionBy monitoring the adult dynamics and fruiting rate of t C.pomonella and G.molesta,the niche breadth,niche overlap,niche similarity,and inter-species competition coefficients of the two heart-eaters in time and space resource sequences were analyzed.The results showed that G.molesta had longer occurrence period,and with the niche breadth index of 0.8644.The similarity of temporal niche of these two pests is 0.7109.The C.pomonella manifested more superiority in space resource utilization and its niche breadth index is 0.9189.The similarity of spatial niche of these two pests is as high as 0.9306.The interspecific competition parameters are K₂/b>K₁,K₁/a>K₂,indicating a coexistence of the two kinds of these two pest.Taken together,our results suggest that G.molesta will be the dominant species when occurred simultaneously with C.pomonella.2)Comparative analysis of P450 genes in C.pomonella and G.molesta.A total of 72 P450s genes were identified through screening the transcriptome of C.pomonella,of which 5 were P450 genes belonging to Clan2,31 were P450s genes belonging to Clan3,and 27 were P450s genes belonging to Clan4.There are 8 P450s genes in microsomes.There are 77 P450s genes in G.molesta,of which 14 are Clan 2 P450 genes,30are Clan 3 P450 genes,18 are Clan 4 P450 genes,and 15 are microsomal P450 genes.The Clan3 family genes all contained typical cytochrome P450 recognition characteristics.The Clan3 group genes of C.pomonella are distributed in 12 subfamilies,which is less than that of G.molesta（14）.Compared with G.molesta,the number of genes was amplified in CYP6A and CYP6B,and obvious contraction was found in CYP6AN,CYP6AE,CYP347A,CYP324A.3)Differences in molecular responses of C.pomonella and G.molesta to plant secondary allelochemicalsThe differences in growth tolerance,P450 enzyme activity,and molecular response of the P450 gene were studied by feeding two kinds larvae of artificial feeds containing plant secondary allelochemicals to the heartworm.The results show that high concentrations of plant secondary allelochemicals 0.1%coumarin and 2%quercetin can inhibit the growth and development of C.pomonella,but have no significant effect on G.molesta.C.pomonella has two P450 genes whose expression levels are up-regulated after feeding on a diet containing coumarin,which is less than that of G.molesta（5）.C.pomonella has one P450 gene whose expression level was up-regulated after feeding 2%quercetin-containing feed,which was less than that of G.molesta（3）.Cp CYP6B4a and Gm CYP6B2 have the most obvious responses to plant secondary allelochemicals.Both genes are highly expressed during the larval stage,and are highly expressed in the tissues of the midgut and Malpighian tube,but lower expression level in the head,cuticle,and fat body.