Abstract:
Objective Endophytic microbes from rice plants that are antagonistic to the pathogen of rice sheath blight were isolated and tested for disease control efficacy followed by optimization of culture conditions.
Method Endophytic microbes were isolated from healthy rice plants and examined for antifungal activity against Rhizoctonia solani using a dual-culture plate assay. An antagonistic strain, S7B4, was identified by polyphasic taxonomy that included the applications of physiochemical characterization and phylogenetic analysis based on concatenated sequences of the 16S rDNA and gyrB genes. Medium, pH, temperature, and flask shaking speed for culturing S7B4 were optimized with antifungal spectrum determined.
Result The bacterium antagonistic to R. solani isolated from the endophytic microbes of rice plants was S7B4, which was subsequently identified to be Pseudomonas stutzeri. It displayed an in vitro inhibition rate of 70.5% on R. solani with mycelia significantly distorted as shown in SEM images. Among the tested culture media, LB, NA, NYBD, CM, and YSP, S7B4 grew best in NYBD with the highest OD600 under pH 8.0 at 30℃ with constant shaking at 210 rpm. In addition to R. solani, the strain was also strongly inhibitive to the growth of 11 other pathogenic fungi, including Colletotrichum camelliae, R. cereadis, Gaeumannomyces graminis, and Fusarium moniliforme.
Conclusion P. stutzeri exhibited a broad-spectrum inhibitory effect against various plant pathogens, especially significant antagonistic against R. solani, the pathogen of rice sheath blight disease. It could be easily cultured for biological control of the disease.
下载: