Effect Of Exogenous Nitric Oxide And Hydrogen Peroxide On Resistance Of Yellow Stunt-root Rot Of Astrgalus Adsurgens

Standing milkvetch is an wildly used forage in northern China. Anew disease is reported by Li called Yellow stunt and root rot. Persistence and productivity were reduced by the disease. Disease-resistance and susceptible varieties of Astrgalus adsurgens were selected and applied with exogenous NO and H2O2, Scavengers cPTIO and As A after inoculating Embellisia astragali spore suspension. Disease incidence, disease index, NO and H2O2concentration, POD, PPO, Glu, Cht, CAT and SOD activity were analy zed to assess the effect of NO and H2O2on disease-resistance of yellow stunt and root rot disease of Astrgalus adsurgens. Experiments of greenhouse and field were carried out. The results are as follows:1. At greenhouse conditions, The results showed that the NO content of two varieties of Astrgalus adsurgens inoculated with Embellisia astragal were higher than uninoculated variety. The highest value of susceptible varieties appeared at24h, arrived2.98umol/g, while the highest value of disease-resistance variety showed at24h, arrived3.38umol/g. Disease incidence and disease index of both disease-resistant and susceptible varieties applied with exogenous NO were the lowest, while varieties applied with cPTIO were the highest. Additionally, all tested enzyme activities increased at different levels as well, and the enzyme activities of disease-resistant variety were higher than susceptible ones, which indicated that exogenous NO can improve its disease-resistance and lower infection of yellow stunt and root rot disease. It also showed there is a close relationship between disease-resistance of Astrgalus adsurgens and NO, disease-resistance was strengthened by regulating the enzyme activity so as to reduce the infection rate. The results showed that the H2O2content of two varieties of Astrgalus adsurgens inoculated with Embellisia astragal were higher than uninoculated variety. The highest value of susceptible varieties appeared at38h, arrived929umol/g, while the highest value of disease-resistance variety showed at24h, arrived986umol/g. Disease incidence and disease index of both disease-resistant and susceptible varieties applied with exogenous H2O2were the lowest, while varieties applied with As A were the highest. Additionally, all tested enzyme activities increased at different levels as well, and the enzyme activities of disease-resistant variety were higher than susceptible one, which indicated that exogenous H2O2can improve its disease-resistance and lower infection of yellow stunt and root rot disease. It also showed there is a close relationship between disease-resistance of Astrgalus adsurgens and H2O2, disease-resistance was strengthened by regulating the enzyme activity so as to reduce the infection rate.2. The results of greenhouse and field were similar. two growing seasons were observed under field conditions. Disease incidence, disease index, plants height and dry weight were analysised. The first annual, incidence and disease index were lower and the result was not significant. the second year it showed that NO and H2O2enhanced disease resistance of Astragalus adsugens. The incidence and disease index increased in2013and disease-resistance varieties were lower than the susceptible varieties each month. Disease-resistance varieties from the beginning of July, susceptible varieties from the beginning of June, NO and H2O2treatment reduced the incidence and disease index, AsA and cPTIO increased incidence and disease index relative to the control. The highest incidence of disease-resistance varieties was cPTIO treatment21.5%and the lowest was H2O2treatment18%. The highest incidence of susceptible varieties was cPTIO treatment30%and the lowest was NO treatment20.5%. Dry weight of disease-resistance varieties was up to262g H2O2treatment, a minimum of AsAtreatment228g. Dry weight of NO and H2O2treatment were significantly higher than the control, AsA and cPTIO treatment were significantly lower than the control (P<0.05). Susceptible varieties showed consistent trend with disease-resistance varieties. NO and H2O2treatment increased plant height and dry weight of disease-resistance and susceptible varieties. Exogenous NO and H2O2can reduce incidence and disease index, improve plant height and dry weight, enhance disease resistance of Astrgalus adsurgens.3、Disease incidence and disease index were reduced (P<0.05) by NO. Treatment with AsA weakened the effect of NO. During the earlier period the H2O2peak was advanced by NO, but during the later period, when the concentration of H2O2was relatively higher, H2O2accumulation was delayed by NO. The continuous increase in SOD、POD、CAT activity induced by NO was inhibited by AsA. The results imply that exogenous NO can enhance the disease resistance of Astrgalus adsurgens. NO may interact with H2O2and exert its effect by modulating the endogenous H2O2level.