Optimization Of Solid State Fermention Conditions Of Streptomyces Albospinus CT205 And Its Preliminary Application

There is a wide range of soil-borne pathogens in the world, which can harm plant roots or even cause the whole plant disease, causing serious economic losses. Biological control is a cost-effective method and overcomes the drawbacks of the physical and chemical control methods, thus has become a hot research topic in soil-borne disease control. Streptomyces albospinus CT205 has a broad spectrum antimicrobial activity against different plant pathogenic fungi. In this study, we investigated the soil-borne diseases of Strawberry in Kirin town and Spring town in the outskirts of Nanjing, and optimized the solid-state fermentation conditions of strain CT205 and developed a bioorganic fertilizer: The feasibility of bioorganic fertilizer was evaluated against the strawberry and cucumber soil-borne diseases.The results were as follows:For the isolation of root rot pathogen of Srawberry, the samples were collected from the Kirin town and Springs town and then isolated the pathogenic fungi by using a conventional tissue separation method. Meanwhile, we detected its pathogenicity by means of Koch law. At last, we acquired three strawberry root rot pathogens. The in vitro antagonism assay showed that the strain CT205 had strong antagonistic effects against these three root-rot pathogens of strawberry. The strain CT205 showed inhibition zones of 9.5 mm,7.5 mm and 9 mm against three root-rot pathogens Y1, Y3 and Y5, respectively. The optimization of solid-state fermentation of biocontrol agent CT205 was done in the following medium:wheat bran 50%, millet flour 12%, soybean powder 6%, rice bran 12%, rice husk 20% and CaCCO30.3%. The ratio of materials to water 1:0.8, initial pH 7.5, inoculum size 15% and fermentation at 28℃ for 6 days were chosen. After fermentation, the bacterial counts were 3.25×108 CFUg=1.The biocontrol effects of strain CT205 and its bioorganic fertilizer were tested against the root rot of strawberry in a pot experiment and Fusarium wilt of cucumber in a field experiment. The results of the strawberry pot experiment indicated that bioorganic fertilizer significantly improved the growth and reduced the disease incidence. The application of CT205 in cropping soil increased the number of fruit per plant, fresh weight of leaf and root by 170.6%,5.8% and 32.5%, respectively, and reduced the disease incidence of strawberry by 50%.The application of CT205 enriched bioorganic fertilizer in soil having pathogens Y3, could increase the number of fruit per plant, fresh weight of leaf and root by 115.4%,3.9% and 22.9%, respectively, and reduced the incidence of strawberry by 66.7%. Microbial flora in strawberry rhizosphere was also improved when CT205 was used. The cucumber field trial showed that applying CT205 enriched bioorganic fertilizer could decrease the disease incidence of cucumber by 67.7% and have an increase of 31.03% in cucumber yield.