Characteristic Against Banana Fusarium Wilt And Optimization Of Fermentation Conditions Of3Bacillus Strains

733bacterial strains were isolated and purified from the soil samples collected from primeval forest,in which three antagonistic bacterial strains among them screened with slab confrontation method, had fairly strong inhibition effect against banana Fusarium wilt.According to morphological observation, physiological and biochemical characteristics and16S rDNA sequence analysis determined the S1, S23were Bacillus subtilis and the strain S3was Bacillus licheniformis.Different concentrations of antagonistic bacteria fermentation filtrate can inhibit spore germination and growth of pathogens effectively, with the increase of concentration of fermentation filtrate, inhibition effect is enhanced.When concentration of the fermentation filtrate of three antagonistic bacteria reached70%, the inhibiting rates at high in-hibition level were46%,57%,50%, respectively. In addition, The growth of mycelial nearby bacteriostatic ring also significantly inhibited the swelling hyphal tip is shown, increased hyphal branching, branch short time interval, and damage, contraction and dissolution of mycelium.To explore the the resistant mechanism induced by the biological control Fungus, we took the banana seedlings from Brazil as subjects and compared the differences between changes in protective enzymes activity, the content of chlorophyll and root activity with different treatments by pathogenic inoculation, irrigating the bacterium suspension liquid of antagonistic fungi and other two different ways. Results showed Seedlings treated with S23bacterium suspension had dramatically improved the activities of CAT, PPO, SOD and POD. The maximum peak of each treatment was bigger than that of correspondent time treatments with3.72,2.03,1.72and2.61times, respectively. S23bacterium suspension could better control the damages from fungus to the chlorophyll on seedlings; the S23antagonistic fungi also improved the root activity of seedlings whenever the pathogenic fungi existed or not.The colonization ability of the strain S23in both soil and root surface of banana were good and the colonization ability of the sterile soil was stronger than that of the organic soil. After being inoculated in soil, the population of strain S23decreased by74.5%in organic soil and increased by10.3%in sterile soil after45days; the population of strain S23on banana root surface in organic soil decreased by52.88%and became1.36times of the initial strain in sterile soils after40days.The strain had some prevention effect on banana wilt, on45day the relative effect was up to40.31%, which w as lower than that of the baijunqing (63.15%). The optimizing conditions of the fermentation of S1, S3and S23are showed: temperature25～35℃,30～35℃,25～35℃; the time of fermentation for biocontrol20h,24h,20h;the inoculation of seeds culture with1%,2%,3%; rotation speed180r/min,180r/min,180r/min; medium volume150mL,150mL and120mL of250ml flask.