| The fruits of Ginkgo biloba contain a variety of microorganisms that can inhibit plant diseases,which can be used as the source of beneficial microbial resources for biocontrol.In order to isolate and purify antagonistic bacteria with biocontrol potential against a variety of plant disease fungi from Ginkgo biloba fruits,the antagonistic bacteria were isolated by plate line method,and the antagonistic effect against plant pathogenic fungi was measured by plate confrontation method.The sporulation rate was improved by screening the carbon and nitrogen sources of the sporulation base medium and orthogonal test.The control effect of bacteria was verified by pot challenge test.In this study,the bacteria with biocontrol effect was isolated and positive by Gram staining,which was preliminarily identified as B.velezensis SP by chemical property analysis and 16S r DNA sequencing analysis.B.velezensis PZ-3 had inhibitory effects on six plant pathogenic fungi,namely,Pyribospora cinerea,Fusarium graminosa,Fusarium fujiura,Curvularia scinocarpus,Fusarium uniqueum and Fusarium oxysporum,with inhibition rates ranging from60%to 69%.Among them,B.velezensis p Z-3 had strong antagonistic effect on Fusarium fujiura,with the inhibition rate of 69.19±0.24%.It had weak antagonistic effect on Curvularia crescent,and the inhibitory rate was 60.47±0.09%.When the soybean peptone was used as nitrogen source,the maximum number of viable bacteria was 3.4×109 CFU·m L-1 and the maximum spore rate was 65.74%±0.87.When the mannitol was used as carbon source,the maximum number of viable bacteria was 5.0×109 CFU·ml-1 and the maximum spore rate was61.63±1.14%.When soybean peptone and mannitol were used to replace tryptone and glucose in spore-producing basal medium,the maximum viable number of Bacillus velezensis PZ-3 was5.2×109 CFU·m L-1,and the maximum spore rate was 74.04±0.64%.At 30?,190 r·min-1,cultured for 80 h,the maximum viable count of Bacillus velezensis PZ-3 was 5.6×109 CFU·m L-1,and the maximum spore rate was 83.58±0.24%.In the corn pot challenge test,the disease index of negative control group was 77.78,and the control effect of experimental group was57.15%.B.velezensis PZ-3 has a good biocontrol effect against a variety of plant pathogenic fungi and can be used as a potential microbial resource for biocontrol production practice.The optimum sporulation nitrogen source was soybean peptone and carbon source was mannitol.The optimum sporulation culture condition was 30?,rotation speed 190 r·min-1 and culture time 80 h.It was proved that B.velevensis PZ-3 had control effect on corn root rot caused by F.fujiura infection. |
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