The Influence Of Different Maize Hybrids(Inbreds) And Tannin And Gallic Acid To The Detoxification Enzymes Of Rhopalosiphum Maidis(Fitch)

The corn aphid,Rhopalosiphum maidis(Fitch),is an important piercing-sucking pest that damage maize plant.In order to explore the role of the plant secondary substances in resistance to aphid of the different maize hybrids(inbreds),in this survey,on the basis of previous studies,we choose 1 main maize hybrid in Henan province and 3 inbred lines with different aphid resistance in corn fields as materials,using the method of artificial inoculation,investigated the population dynamic of R.Maidis on the four tested plants,measured the relative gene expressions and activities of the detoxification enzymes of third instar R.Maidis feeding on different maize hybrids(inbreds).Afterwards,we feeded the third instar aphid with artificial diet adding with plant secondary substances,analyzed the influence of tannins and gallic acids,the main secondary substances of maize plant,to the key detoxification enzyme activities and their relative gene expressions of third instar R.Maidis.The main results were as follows:(1)Using the method of artificial inoculation,the population dynamic changes of corn aphids on 4 maize hybrids(inbreds)were studied.The results showed that the population of R.Maidis on the 4 tested maize hybrids(inbreds)have the same change trend,but the peaks and peak stage of the population differed with the hybrids(inbreds).The population decreased during the few days after inoculation because of the new environment,but increased rapidly with the time went by.when the tassel completely sprout,the R.Maidis transferred to damage on female ear,and re ACh Ed the population peak at filling stage.afterward,the number of population of R.Maidis declined sharp until to zero with the gradually maturity of maize plant.Generally,the peak period of the aphid on resistant maize plant was delayed along with the population quantity at peak time decreased.(2)The activities of detoxification enzymes and their relative gene expressions of the third instar R.Maidis on 4 different maize hybrids(inbreds)were researched using the spectrophotometer and real-time fluorescence quantitative PCR technology.The results showed that the CYP450,Car E and ACh E activities of the aphid feeding on Zhengdan958 were significantly enhanced,the relative expressions of CYP4,CYP6,Car E and ACh E genes were significantly up-regulated,but the GST activity and its relative gene expression were inhibited.(3)The activities and relative gene expressions of the detoxification enzymes of R.Maidisfeeding on artificial diet containing the different levels of tannins and gallic acids were researched.We found that the relative expression of Car E,CYP4,CYP6 and ACh E genes were all up-regulated with the increased concentration of tannins and gallic acids in artificial diet,but GST was the only exception.GST enzyme activity of the aphid re ACh Ed the highest at the concentration of 0.65% tannin and 0.60% gallic acid,respectively,and the enzyme activities of both Car E and CYP4 revealed the highest at the concentration of 1.55% tannin and 1.80% tgallic acid respectively,but ACh E enzyme activity has no obvious change with the increased concentration of plant secondary substances.(4)The influence of feeding times of the third instar aphids on artificial diet mixed with1.55% tannin and 1.80% gallic acid concentration respectively to the key detoxification enzymes activities and their relative gene expressions of the aphids were measured.The results indicated that the relative gene expressions of CYP4,CYP6,Car E and ACh E of the aphids feeding on both tannin and gallic acid were all up-regulated.The relative gene expression of GST of the aphid feeding on tannin was significantly up-regulated when feeding for 6-24 hs,but it had no significant change when feeding on gallic acid.The GST enzyme activity of the aphid decreased at the early stage of feeding,and increased from 6h after feeding;CYP450 enzyme activity showed an increasing trend with prolonging feed time.Car E activity was first increased and then decreased after feeding for 6h,but the enzyme activity of the aphid feeding with tannin and gallic acid were significantly increased at feeding for 24 h,whereas ACh E activity showed no significant change with the feeding time.In conclusion,the population dynamics of R.Maidis were relatively consistent on different maize hybrids(inberds)with different aphid resistance,but the paek stage was delayed and the population at paek stage was decreased for the aphid feeding on resistance hybrid,Aphid-resistance of maize plant influence the key detoxification enzymes activities and relative gene expressions of the aphid,and tannin and gallic acid,two kinds of palnt secondary substance,can induce Car E and CYP450 activities and relative gene expressions of R.Maidis,but showed no effect on the ACh E enzyme activity.The aphid-resistance of maize plant was closely related to the content of tannin and gallic acid,and the adaptation of R.Maidis to their host plants may be related to the metabolise of the secondary substances of R.Maidis detoxification enzymes.