Efficacy of Streptomyces padanus PMS-702 for controlling rice sheath blight

• Main Authors: Chia-Jung Yang, 楊佳融
• Other Authors: Jenn-Wen Huang
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/5devu6

碩士 === 國立中興大學 === 植物病理學系所 === 106 === Rice sheath blight (ShB), caused by Rhizoctonia solani Kühn AG1-IA, is one of the destructive diseases in rice fields worldwide. The pathogen infects all growing stages of rice, especially at tillering and boosting stages. In Taiwan, ShB disease causes 14-17% yield loss every year. Although the application of fungicides could control the disease, developing more friendly strategies for the disease management is needed due to the occurrence of fungicide-resistant pathogen and environmental concerns. The purposes of this study were to develop biological control strategies focusing on field sanitation and spraying rice plants with a biocontrol agent for ShB disease management. Streptomyces padanus PMS-702 showed a great antagonistic activity against R. solani isolates RS1-731 and RS1-024 on potato dextrose agar plates. Fungichromin was found to be the major compound produced by S. padanus PMS-702 for inhibiting mycelial growth of R. solani. The results revealed that fungichromin at 3.07 mg/L could inhibit 50% mycelial growth of the pathogen. In addition, fungichromin could also cause leakage of cytoplasm and inhibit the formation of infection structure of R. solani. Fungichromin could reach as high as 802 mg/L when S. padanus PMS-702 was cultured in malt extract-alfalfa seed meal liquid medium for 6 days. Addition of 0.5% (v/v) S. padanus PMS-702 fermented broth into soil decreased the survival rate of the pathogen on rice straws compared to the control. Soil amended with 0.5% (v/v) S. padanus PMS-702 broth and 0.5% (w/v) tea seed pomace resulted in the death of R. solani mycelia in the infested rice straws and inhibited the germination of sclerotia 21 days after treatment. Greenhouse assays revealed that S. padanus PMS-702 cultured in soybean meal-glucose (SMGC-2) medium after mixing with different surfactants could enhance its efficacy for inhibiting the pathogen. Of six surfactants tested, the addition of 2% tea saponin was the most effective in suppressing the pathogen. S. padanus PMS-702 broth fermented in SMGC-2, mixed with 2% tea saponin, diluted 100 fold, and sprayed onto rice plants significantly reduced ShB disease severity ranging from 24.04 to 66.67%. Thus, S. padanus PMS-702 is an effective biocontrol agent. The results demonstrated that the efficacy of S. padanus PMS-702 for controlling rice ShB disease could be significantly improved through culture-based fermentation.