Identification Of Strawberry Fungal Pathogens And Indoor Virulence Determination And Screening Of Antagonistic Bacteria

Strawberry（Fragaria ananassa Duch.）is an important berry cash crop,and strawberry is also processed into various foods in addition to fresh food.In recent years,the yield of strawberry in China has increased year by year,followed by the increase of strawberry diseases.Therefore,the pathogenic strains and characteristics of strawberry diseases,the screening of efficient agents,and the screening of antagonistic bacteria can lay a theoretical foundation for the prevention and control of strawberry diseases.In this study,were conducted the morphological and molecular identification,were determined the pathogen species through the indoor virulence determination.Endophytes and rhizosphere bacteria were isolated in the root leaves and rhizosphere soil of healthy strawberry;two fungal pathogens were the target bacteria,and the antagonistic bacteria were screened by morphological,physiological and molecular identification.To study the hydrolase activity of the antagonistic strains and the observation of the pathogenic bacteria after antagonistic treatment,the effects of the antagonistic cell suspension and the supernatant against the two diseases were verified.The main test results of this study are as follows:1.Two fungal pathogen strains causing strawberry brown leaf spot disease and strawberry stem withered leaf spot disease were isolated and purified by tissue isolation method.Through morphological identification and combined with multigene molecular biological analysis,the pathogenic bacteria of strawberry brown leaf spot disease were P.concavum and S.pogostemonis,respectively,among which S.pogostemonis infection caused by strawberry was the first discovery report.2.The growth rate method of the two strains showed that the best antibacterial effect on strawberry brown leaf spot was 450 g·L^-1,and its EC₅₀value was 2.4497 mg·L^-1.The best antibacterial effect on strawberry stem and leaf spot was 30%water dispersion medium,with an EC₅₀value of 0.0025 mg·L^-1.In the verification test of in vitro leaf prevention,the two agents had good prevention effects on strawberry brown leaf spot and strawberry stem withered leaf spot on in vitro leaves.3.A total of 183 and 55 rhizosphere bacteria form Root-stem leaves and rhizosphere soil of healthy strawberry were isolated by tissue isolation and gradient dilution.Ten rivalry strains of strawberry brown leaf spot disease and leaf spot blight were screened by flat dish confrontation,Combining morphological,physiological,biochemical and molecular biological analysis,G3-23,J3-20,and G3-29 Strainswere initially identified as B.beles（B.svelezensis）,J1-4,G2-12,G3-K2,J1-11,and J6-1 were identified as（B.subtilis）,G3-20 was identified as salt-tolerant（B.halotolerans）,G3-17 was identified as（B.cereus）;The results of antibacterial assdetermination showed that,Nine of these bacterial strains had broad-spectrum antibacterial activity.4.Tthe strain of G3-23 with the best antagonistic effect in the dish,was selected the morphology of pathogenic bacteria after antagonistic treatment,and the resultshand that the antagonistic bacteria would destroy the outer wall of pathogenic bacteria;the hydrolase determination test to G3-23 strain had protease and cellulase activity;The strain of G3-23 cell suspension and supernatant had good prevention effect on strawberry brown leaf spot disease and strawberry stem withered leaf spot,and strain G3-23 showed good control potential.