Study On Screening Antagonistic Bacterium Strain FJ1for Pear Scab And Antagonistic Mechanism

Pear is business fruit second only to apple in our province, with nearly one million mu of cultivated area, has formed a large-scale industry.But in recent years, with the expansion of the scale, pearscab, rot, rust and other common diseases in pear cultivation caused serious harm, directly impacted on pear appearence and quality, caused a great threat to the pear industry in our province.The study aimed on separating the bacteria from pear rhizosphere soil, yak dung, vermicompost samples, and eventually obtained the strains FJ1which has a better antagonistic action for the pear scab pathogen by screening and rescreening,to explore a green, efficient, and safe new microbial agents for the pear scab pathogen. The present study was undertaken in antagonistic Bacillus stains identification, optimization of fermentation process and field trials.55bacterial strains were isolated from different pear rhizosphere soil, yak dung, and vermicompost,13out of which were revealed antagonistic effect on the pathogen of pear scab wilt in the plate confrontation assay and plate-well tests. And use the plate method for rescreening to get a better inhibition strains FJ1, the strains FJ1fermentation broth of pear scab pathogen inhibitory rate reached64.1percent.Based on morphologic, physiological, biochemical characteristics and16S rRNA sequence analysis, can be determined that strain FJ1belong to Bacillus subtilis.Considering viable count in fermentation broth,and the antagonistic activity of strains FJ1as measure to find the optimal fermentation medium. The experimental results showed that the antagonistic bacteria FJ1liquid fermentation medium’s best carbon source was glucose, the best nitrogen source was ammonium chloride,and the best optimal culture conditions of bacteria FJ1are:initial pH7.0, shake flasks of liquid volume60ml/250ml, culture time30-36h, temperature28℃。Field test results showed that the fermentation broth for FJ1spraying can be effective in reducing the incidence of pear scab and susceptible varieties of pear and has a goodprotective effect. The effective number of viable cells in the fermentation broth of up tol08/ml, in the leaves, fruit surface of the dominant species, play antagonistic effect,inhibiting the growth of black spot disease pathogens. At the same time, the surface of antagonistic bacteria in plant growth and can provide long-lasting and stable antagonism, unlike chemical fungicide control effect decreased over time, the fermentation broth diluted FJ1still contain a high number of viable cells, to maintain better control effect, the cost savings of prevention.