Identification And Characterization Of Bacteria Antagonistic To Rhizoctonia Cerealis

Wheat sharp eye-spot caused by Rhizoctonia cerealis Vander Hoeven is an important soil-borne wheat disease in the middle and lower basin of Yangtze River. Many research indicated that there was a lot of bacteria in the rizhosphere of wheat, including Pseudomonas spp, which could control wheat sharp eye-spot. In this study, bacteria strains A6, A12, B37, B40, B41, B42, B52, B30, B31, B32, B43 and B52 isolated from wheat rhizosphere in Jiangyan City of Jiangsu Province were identified with their 16S rDNA sequences, physiological and chemical characters. The results indicated that strain A6, A12, B37, B40, B41, B42 and B52 were P. fluorescens, and strain B30, B31, B32, B43 and B52 were identified as Bacillus spp..It is valuable to determine the control efficiency of P. fluorescens to R. cerealis and the colonization of antagonistic bacteria in the rhizosphere of wheat. In greenhouse, all tested 7 bacteria strains decreased wheat sharp eye -spot index, the control efficiency of strain B42 to the disease reached 71.67%. By the antibiotic marker method, we also revealed that strain A6^Rif+, B41^Rif+ and B42^Rif+ could colonize on the wheat roots and basal-stem at 30 th day after inoculation.P. fluorescens could control many soil-borne plant diseases, the mechnisms are often assoiated with production of some antibiotics such as 2, 4-DAPG, PCA, PLT and so on. Molecular biology and chemistry technology were used to detect the production of these antagonistic substances. The results indicated that all the 6 strains didn't produce 2, 4-diacetylphloroglucinol, phenazine or pyoluteorin. Pyrrolnitrin production related gene PrnD was detected in the strain A12, B37 and B42. In strain B37, another pyrrolnitrin production related gene PrnC was also detected. Strains A12, B37and B42 produced siderophore, strains A12, B40, B41 and B42 produced proteinase, and all the strains didn't produce chitinase.