Diversity Research Of Soil Microbial Community In Banana Orchards Infected With Fusarium Wilt Disease And Screening,Identification Of Antagonistic Streptomyces

Banana Fusarium wilt disease, widely distributed over the main banana-producing regions in the world, is one of systemic vaseular disease caused by Fusarium oxysporum f. sp. Cubense. Biologicalcontrol is one of the important methods to control banana Fusarium wilt disease for its safety and effectiveness. Soil microorganism plays an important role in soil organic matter decomposition and environmental remediation, and its diversity reflects soil environment quality to some extent. Plants soil-borne diseases have certain relationship to diversity of soil microbial communities. Therefore, research on diversity of soil microbial communities in banana orchards infected with wilt disease and application of efficient antagonistic microbe are of important practical meaning.In this study, soil samples including3infected samples and3disease-free samples, were collected in banana orchards in Lingao, Hainan. T-RFLP was used to analyze diversity of microbial community and qualitatively analyze the primary microorganisms in the soil samples. Physicochemical property of samples were determined by conventional methods to analyze its relationship to soil microbial community composition. Antagonistic actinomycetes were isolated by pour plate method from soil samples, and selected by confrontation culture method against Fusarium oxysporum f. sp. Cubense Race4. Activity assessment of antagonistic streptomyces against Fusarium oxysporum f. sp. cubense Race1and race4, Curvulatia fallax, Colletotrichum gloeosporides, and Alternaria tenuissima was determined by the methods of flat growth restraint, mycelial growth and spore germination. Strain was identified by morphological and cultural traits, physio-biochemical characteristics and16S rDNA sequence and phylogenetic analysis. The main conclusions are as follows:(1) The content of available P and pH of soil in infected banana orchards were lower than those of disease-free orchards in the same area, and the difference was significant.(2) Diversity of soil microbial communities in infected banana orchards was richer than that of disease-free orchards. The primary microorganisms of soil in infected banana orchards were Cytophaga sp., Bacillus subtilis, Staphylococcus arlettae str.and Eubacterium ruminantium str.. Those of disease-free orchards were Bacillus subtilis str., Bradyrhizobium sp.-. Rhodopseudomonas palustris str., Staphylococcus arlettae str. and Eubacterium ruminantium str.. (3) There was a certain correlation between soil physicochemical property and Simpson’s Index based on T-RFLP. And soil physicochemical property had an effect on quantity and distribution of most soil microorganisms.(4) An antagonistic streptomyces against Banana Fusarium Wilt Disease Strain A2-g+-41was isolated and selected. It was identified as Streptomyces spectabilis by morphological and cultural traits, physio-biochemical characteristics and16S rDNA sequence and phylogenetic analysis.(5) Strain A2-g+-41had significant inhibition to7kinds of pathogenic fungus such as Fusarium oxysporum f. sp.cubense, Glorosprium musarum Cookeet Mass and so on. The radius of inhibition zone on PDA plates ranged from11.00mm to14.93mm. The inhibition rates to mycelium growth of pathogenic fungus ranged from23.89%to74.89%. The inhibition rates to spore germination reduced with the dilution multiple of fermentation increasing, and fermentation without dilution had the biggest inhibition rates ranging from83.12%to93.96%. It may be a new microbial resources for biological control.