Isolation and Identification of Antagonistic Actinomycetes and Their Application in the Biocontrol of Fusarium oxysporum f. sp. cucumerinum

To obtain antagonistic actinomycetes against plant pathogen,Fusarium oxysporum f.sp.cucumerinum,about 44 strains of actinomycetes with antagonistic activity were isolated from various soil samples.Through the primary and secondary screening,the strain XF-7 showed the most efficient antagonistic activity among all tested strains.Moreover,the effects of fermentation broth of strain XF-7 on mycelium growth,spore germination of F.oxysporum f.sp.cucumerinum,seed germination of cucumber were tested,and the clay-pot experiments on the biocontrol effects of fermentation broth on seedling fusarium wilt were conducted.The results indicated that the fermented broth of strain XF-7 had a significant inhibition on the mycelium growth and spore germination of plant pathogen,and had a stimulative effect on seed germination of cucumber,the control efficacy against seedling fusarium wilt of cucumber was significantly up to 79.57% as compared to the control.The 16S rDNA sequence of strain XF-7 shared 100% homology with Streptomyces toxytricini,strain XF-7 was morphologically and molecularly identified and named as S.toxytricini XF-7,with GenBank accession number JN315670.