Study On The Effect Of Exogenous MeJA On Enhancing The Resistance Of Pepper To Bemisia Tabaci(Gennadius)

The whitefly Bemisia tabaci(Gennadius),belongs to the Aleyrodidae within the Hemiptera.It is a notorious pest on greenhouse vegetables and has been reported serious damages almost all around Jiangsu province.On greenhouse growth Capsicum annuum(pepper),one kind of the main vegetable varieties in Jiangsu province,infestation of B.tabaci has caused serious impact on yield and quality.The research of Methyl jasmonate(MeJA),a multifunctional plant growth regulator,was focused more on the regulation of vegetable quality but less on the insect resistance and volatiles compounds of vegetable.In this paper,the influence of exogenous MeJA on B.tabaci were studied by using the susceptible pepper Sujiao 15 and resistant pepper Xinsujiao 5 as experimental material.The nutrient contents,the secondary metabolites contents and the digestive enzymes and protective enzyme activities were measured after MeJA spray.The main results are as follows:(1)Using Sujiao 15 and Xinsujiao 5 peppers as experimental materials,the influence of exogenous 10-5 mol/L MeJA spray for 48 h on the host selectivity,development period and survival rate and the population dynamics of B.tabaci were determined.Our results showed that the selection rate of B.tabaci was significantly reduced compared with untreated,and the selection rates of susceptible varieties and resistant varieties decreased by 64.84%and 75.41%,respectively.Feeding on the peppers treated with MeJA,the development period of B.tabaci was significantly extended and the survival rate was significantly reduced.Among them,the development period of susceptible varieties and resistant varieties were extended by 7.66 d and 9.66 d,respectively,and the survival rate was decreased by 10.5%and 9.89%;for the susceptible variety Sujiao 15,the MeJA treatment mainly prolonged the whitefly eggs,fourth-instar nymphs and pseudo-pupa stages,while for the insect-resistant variety Xin Sujiao 5,the induction effect was throughout the whole process of development.After spraying MeJA on field peppers,the population of B.tabaci declined rapidly,and with the extension of the treatment time,the population continued to decline.(2)Spray pepper with MeJA solution at 3 concentrations of 10-4 mol/L,10-5 mol/L,10-6 mol/L and the nutrient and secondary metabolite content of the pepper and resistance-related enzyme activity were determined 1d,2d,3d after treatment.The results showed upward trend of the content of chlorophyll a,chlorophyll b,total chlorophyll,soluble sugar,proline and total phenols in pepper leaves displayed and decreased trend of flavonoids with the increase of the concentration of MeJA.The activities of POD and CAT in pepper leaves were also significantly enhanced after treatment and were positively correlated with the concentration of MeJA and the treatment time;However,time showed no significant effect on SOD activity.After feeding peppers treated with MeJA,the activities of trypsin and chymotrypsin in B.tabaci were significantly reduced compared with trose of control;After 48 h of feeding the susceptible varieties,the activities of the two digestive enzymes were both stronger than those of 24 h.However,there was no significant difference in the activity of the two digestive enzymes at 24 h and 48 h after feeding resistant varieties.(3)Pepper volatiles were collected byusing solid phase microextraction and the volatile components in it were determined by using method of GC/MS.Our results showed that the treatment of exogenous MeJA resulted in 13 types of volatile substances new occurred and 5 types lost in Sujiao 15 compared with that of untreated;While in Xinsujiao 5,treated with exogenous MeJA displayed 7 more new occured volatile substances and 2 types lost compared with the untreated.The content of hexenal and(E)-?-ocirene,which have a strong repellent effect on B.tabaci,were significantly increased after exogenous MeJA treated,while the content of hexenal in the susceptible pepper variety Sujiao 15 increased by 74.67%.The results of the study indicated that exogenous MeJA reduce the selectivity of B.tabaci to peppers mainly by induces the up-regulation of anthelmintic volatiles in peppers;Exogenous MeJA could induced the up-regulation of nutrients and secondary metabolites related to B.tabaci resistance in peppers,and inhibited the digestive enzyme activity of B.tabaci,and reduced the growth rate and survival rate of B.tabaci.From our study,we could inferred that exogenous MeJA may control the B.tabaci population by improving the selectivity and resistance of pepper to B.tabaci.