Preliminary Study On Resistance Mechanism Of Bacillus Subalpine Yellow-soil Bacillus CQ07 To M.oryzae

Rice blast is one of the three major diseases affecting rice production and quality.At present,the cultivation of resistant varieties and the application of chemical pesticides are the main methods to control rice blast.Because rice blast fungus is very easy to mutate and form new physiological small species,the breeding cycle of resistant rice is too long,and chemical pesticides have serious harm to human health and environmental security,it is very important to find effective prevention and control methods of rice blast for food security.In recent years,more and more attention has been paid to the use of the antagonistic action of organisms and their metabolites to control crop diseases and insect pests.In this study,a bacterium named CQ07 was isolated and screened from subalpine soil in western Sichuan.Through the morphological observation,physiological and biochemical characteristics analysis and molecular biological identification,CQ07 was identified as Bacillus Australimaris.The inhibition mechanism of CQ07 fermentation broth on blast fungus Guy11 was investigated.The microscopic observation showed that the CQ07 fermentation broth had obvious delayed and inhibited the germination and appressment of M.oryzae,and the abnormal phenomena of expansion and shrinkage were also observed in the bud tubes of conidia produced by the fermentation broth of M.oryzae.The experimental observation of FDA-PI composite dyes on mycelia of M.oryzae also proved that CQ07 filter broth could destroy the integrity of membrane,and mycelia also showed abnormal phenomena of expansion,shrinkage and vacuole.The vitro leaf experiments showed that the infectivity of conidia treated with filtrate fermentation liquid to the leaves of Lijiangxintuan was lower than that of the control group,and the leaf spot was smaller than that of the control group.Field experiments were carried out to confirm that the number of leaf plague spots in the seedling stage of Lijiangxintuan was also reduced.The experiment of preventing and controlling rice blast in seedling stage and heading stage of Jiangnanxiangnuo was carried out with filtrate fermentation liquid,the experiment showed that CQ07 filtrate inhibited leaf plague in seedling stage and neck plague in heading stage.The active substances in CQ07 filtrate were separated and purified by organic extraction polarity detection,column chromatography and high performance liquid chromatography(HPLC).The results showed that ethyl acetate could extract the active substance,and then the crude substance was separated by MCI column chromatography and silica gel column chromatography.Then the active substances obtained by column chromatography were separated by HPLC and their relative molecular weights were determined by LC-MS.