The Lethal Effect Of Trans-anethole And Beauveria Bassiana Against Myzus Persicae And Their Effect On The Expression Of GSTs Genes

The green peach aphid,Myzus persicae,is an important agricultural pest throughout the world.The long-time use of chemical pesticides lead to the insecticide resisitance in M.persicae.Trans anethole and Beauveria bassiana have the potential to be biological insecticides in the control of pest insects,however,researches on the application of trans anethole and B.bassiana on M.persicae management are limited.In this study,we investigated whether the mixture of trans anethole and B.bassiana has lethal and synergy effects on M.persicae.Furthermore,for the purpose to study whether the glutathione S-transferase(GST)genes are response to the stress induced by trans anethole and B.bassiana,we investigated the expression patterns of GST genes in M.persicae treated with the two stressors.The results are as follows:1.Bioassays on M.persicae with trans anethole and B.bassianaThe M.persicae individuals were treated with B.bassiana(strain Bbr84).The results showed that the conidial suspension caused the highest mortality on M.persicae at the concentration of 108 conidia/mL,and the corrected mortality and LT50 at six days after the treatment were 82.96%and 3.83 d,respectively.The correct mortality of M.persicae were 56.83%,88.64%,64.78%and 53.42%,respectively,after treated with the mixture of B.bassiana(7×107 conidia/mL)and trans anethole at 0.0375,0.0750,0.1500 and 0.3000 mg/mL,respectively.These data indicated that,the mixture of B.bassiana conidial suspension at 7×107 conidia/mL and trans anethole at 0.0750 mg/mL works best for M.persicae control.2.Identification and Bioinformatic Analysis of M.persicae GST GenesBy searching the transcriptome dataset of M.persicae,nine cDNA sequences of GST genes were identified(MperGSTd1,MperGSTd2,MperGSTd3,MperGSTo1,MperGSTs6,MperGSTs1,MperGSTs2,MperGSTtl and MperGSTt2a).The length of the coding regions of 9 cDNAs ranged between 132-185bp.The sequence characteristics and phylogeny of these genes were analyzed using bioinformatic programs,and the classification of the nine M.persicae GSTs were determined.The results also showed that the nine M.persicae GSTs had close relationship with GSTs from other hemipteran species,but not closely related with GSTs from other insect orders.3.Effects of trans anethole and B.bassiana on the GST activity and GST gene expression in M.persicaeThe M.persicae individuals were exposed to B.bassiana(108 conidia/mL)and trans anethole(0.25 mg/mL),and the GST activity and GST gene expression were investigated at 3,6,and 12 h after the exposure.The result showed that the GST activity in M.persicae was significantly increased in response to B.bassiana,but significantly decreased in response totrans anethole.The nine GSTs genes of M.persicae were differentially expressed at different developmental stages as well as in response to trans anethole and B.bassiana exposure.Most genes were highly expressed in fourth-instar nymphs;the transcription levels of some genes were significantly changed at different time intervals after treated with trans anethole and B.bassiana.The mRNA level of MperGSTs2 in trans anethole-treated M.persicae was upregulated more than ten-fold compaired with that in control individuals.