Defense Function Analysis Of Three Host Secondary Substances For Different Biotypes Of Sitobion Avenae

Sitobion avenae(Fabricius)is one of the important pests on cereal crops around the world.Studies have shown that this aphid has undergone biotype differentiation in China.In order to explore the effects of plant secondary substances on the formation of different biotypes of S.avenae,three substances(i.e.,gramine,gallic acid and coumarin)were tested in this study using different concentrations.Carboxylesterase and glutathione-s-transferase activities and the expression of these detoxification enzyme genes are analyzed,and the main findings are as follows:1.The effects of secondary substances on the survival time and fecundity of various aphid biotypes were investigated by feeding aphids with artificial diets containing different concentrations of these substances.The results showed that the survival time and fecundity of aphids in different biotypes of Sitobion avenae varied when feeding on artificial diets with three kinds of secondary substances at different concentrations.The survival time of ZY2 and ZMB54 was significantly shortened after feeding on the diets with 4 kinds of concentrations of gramine,while the survival time of aphids was significantly shortened for HM29 only under the treatment of 0.32 mM and 1.25 mM gramine.Under 4 kinds concentrations of gallic acid,the survival time of three species of Sitobion avenae was significantly lower than that of control,but the trend of change between the concentrations was not consistent.The survival time of ZY2 and ZMB54 aphids was significantly shortened with the increase of concentrations under the treatment of coumarin.Under the treatment of gramine,the number of aphids in three biotypes was significantly lower than that of control,and the number of aphids in HM29 and ZMB54 decreased significantly after ingestion of gallic acid,and the number of aphids in ZMB54 decreased with the increase of coumarin concentrations.2.RT-qPCR was used to analyze the gene expression levels of detoxification enzymes in three biotypes of Sitobion avenae under different concentrations of secondary substances.The results showed that there was no significant difference in the expression of carboxylic esterase gene SaveCarE1,SaveCarE2 and SaveCarE3 in various biological S.avenae under different concentration gramine treatment conditions.Compared with the control,the SaveGST1 expression of HM29 was significantly reduced after the treatment of gramine in each concentration.In addition,the SaveGST3 expression of ZY2 was significantly higher than that of ZY2 and ZMB54 under the conditions of control and concentration gramine.Under the condition of different concentration of Gallic acid treatment,the SaveGST1 of biological HM29 was significantly reduced,while SaveGST3 and SaveGST4 were significantly increased.The expression levels of SaveCarE1 ? SaveCarE3 and SaveGST1 in ZMB54 were significantly reduced in treatments compared to those of control,and the expression of SaveGST2 in ZY2 was lower only under concentrations of 0.004% and 0.008%.There were no significant differences in the expression of CarEs and GSTs in the three biotypes under different concentrations of coumarin.3.The effects of test substances on the activity of CarEs and GSTs showed that the CarEs activity of biotype ZY2 could be significantly inhibited after feeding under different concentrations of gramine.The activity of CarEs of HM29 and ZMB54 was the lowest when the concentration of gramine was the lowest.The maximum GSTs activity of biotype HM29 was significantly higher than that of the control group.The activity of GSTs was significantly higher in ZY2 treated with 1.25 mM gramine than in the control group,and ZMB54 was treated at 0.32 mM.,GSTs activity increased.After feeding different concentrations of gallic acid,the CarEs activities of biotypes HM29,ZY2 and ZMB54 were highest at 0.08%,0.008% and 0.04%,respectively;the GSTs activities of ZY2 and ZMB54 were significantly lower than those of the control group,while HM29 was significantly lower than that of the control group.GSTs activity was significantly increased.After feeding under different concentrations of coumarin,the CarEs activity of HM29 did not change significantly,while the CarEs activity of ZY2 decreased significantly under the treatment of 0.0325%.In addition,the CarEs activity of ZMB54 was at 0.003%,0.0325% and 0.065% coumarin.The GSTs activity in biotypes ZY2 and ZMB54 showed different patterns of a decreasing trend,while the activity of GSTs was significantly increased under the concentration of 0.003% coumarin in HM29.In summary,after feeding on artificial diets containing secondary substances,the survival time and fecundity of S.avenae adults in treatment groups were significantly lower than those of control groups.The detoxification enzyme activities and gene expression patterns varied among different S.avenae biotypes under different treatments.These results indicated that plant secondary compounds could play an important role in biotype differentiation of S.avenae.Our results are significant in deepening the understanding of aphid biotype differentiation on different host plants.