水稻纹枯病菌拮抗菌CZB40的筛选、鉴定及其发酵条件优化

Screening,identification and optimization of fermentation conditions of the antagonistic strain CZB40 against Rhizoctonia solani

为获得对水稻纹枯病有生防效果的拮抗放线菌，以水稻纹枯病菌（Rhizoctonia solani ）为指示菌，从湖南郴州天鹅山风景区土样中分离筛选出5株拮抗放线菌株，其中菌株 CZB40无菌滤液的5倍稀释液对指示菌菌丝生长抑制率高达90.45%，能使菌核菌丝萌发指数降低56.30%，而且能显著抑制菌核的形成。经形态观察、培养性状、生理生化鉴定，并结合16S rDNA 序列分析，将 CZB40菌株鉴定为极暗黄链霉菌（Streptomyces fulvissimus ）。抗菌谱研究表明，该菌株对稻瘟病菌（Magnaporthe grisea ）、桃褐腐病菌（Monilinia fructicola ）、辣椒疫霉病菌（Phytoph-thora capsici ）、草莓灰霉病菌（Botrytis cinerea ）和辣椒白绢病菌（Sclerotium rolfsii ）都有拮抗作用，抑菌率达27.94%～85.71%。通过单因子变量法和均匀设计法对菌株 CZB40进行发酵条件研究。结果表明，其最佳的发酵条件为：玉米粉25 g/L、酵母粉5 g/L、MgSO40.2 g/L、NaCl 0.8 g/L、K2 HPO40.4 g、水1000 mL、29℃、pH 6.0。经优化后，菌株 CZB40无菌滤液的10倍稀释液对水稻纹枯菌丝生长抑制率最高，达到94.85%，比优化前明显提高。该研究结果为水稻纹枯病的生物防治提供科学依据。

To obtain antagonistic actinomycetes for biocontrol of rice sheath blight,five antagonistic actinomyce-tes strains were isolated from soil samples in Chenzhou Swan Mountain of Hunan Province.Among these samples, the 5 diluted sterile filtrate of CZB40 strain exhibited the highest antagonistic activity,showing 90.45% myceli-al growth inhibition and leading to decrease of mycelial germination index by 56.30%.In addition,the formation of sclerotia could be significantly inhibited.By studying the morphology,culture characteristics,physiological,bi-ochemical tests and 1 6S rDNA analysis,CZB40 was identified as Streptomyces fulvissimus .Further antimicrobial spectrum research demonstrated that the strain CZB40 had antagonism against Magnaporthe grisea ,Monilinia fructicola ,Phytophthora capsici ,Botrytis cinerea and Sclerotium rolfsii ,with the inhibition rate from 27.94% to 85.71%.The fermentation conditions were optimized by using the method of one variable and uniform design. The optional fermentation conditions for antibacterial substance production of CZB40 were shown as followed：corn flour 25 g,yeast 5 g,MgSO4 0.2 g,NaCl 0.8 g,K2 HPO4 0.4 g,water 1 000 mL,fermentation temperature 29 ℃ and pH 6.After optimization,the mycelial growth inhibition rate increased significantly up to 94.85% with 10 times sterile filtrate compared with previous fermentation conditions.The results provided scientific evidence in biocontrol of rice sheath blight.