Screening And Control Effect Of Biocontrol Bacteria Against Tomato Root Rot

This study screened a bio-control strain that have inhibitory effects on Fusarium oxysporum.After optimized fermentation medium of resistant strains,we did the study about the control effect of the strain on the tomato root rot,and the ability of the strain to colonize on tomato plants and promote on the growth of tomato plants,thus offer the theoretical foundation for the biological control of tomato root rot.The main research results are as follows:1.The strain XF was isolated from the soil of healthy tomato roots,which had a strong antagonistic effect on F.oxysporum.The inhibitory rate of the strain XF on F.oxysporum can reach 67.50%.After morphological observation and 16S rDNA molecular identification,the strain XF was determined to be Bacillus amyloliquefaciens.2.The F.oxysporum was used as the indicator bacteria,and its antibacterial rate was determined as an indicator,we optimized fermentation medium of the strain XF,and used orthogonal optimization to optimized it better.The results showed that the optimal medium for fermentation of strain XF were: glucose 10.00%,yeast powder 5.00%,MgSO₄·7H₂O 10.00%,（NH₄）₂SO₄ 10.00%.3.The control effect of strain XF and the analysis of antibacterial substances: Salkowski colorimetric test results showed that the fermentation broth of strain XF contained auxin（IAA）;the secondary metabolites of strain XF were detected by the plate verification method,and showed that the secondary metabolites of strain XF contain β-glucanase,amylase and protease;Observation by optical microscope showed that compared with normal hyphae,the ends of F.oxysporum was enlarged and thicker,nternodes shrunk,branches increased,and the hyphae have vesicle-like deformities after the fermentation broth was processed;the spore germination rate of F.oxysporum was significantly reduced after the fermentation broth was processed;detected the antibacterial substances of strain XF by the flat double button method and high temperature sterilization,the test results showed that the fermentation product of strain XF contains volatile substances and high temperature resistant substances.4.The Colonization in tomato root and growth-promoting effect of strain XF : The results of the colonization of strain XF in tomato root showed that the bacterial colonization amount of embryo seedlings was the highest at 10 days;the results showed that the sterile fermentation filtrate of strain XF could promote the germination of tomato seeds,and the filtrate diluted 50 times had the best effect on the germination of tomato seeds;the results showed that the sterile fermentation filtrate diluted by 50 times could promote the growth of tomato plants,and the height of the stem and leaf of tomato plants increased significantly.