橡胶褐根病拮抗放线菌17-7的筛选、鉴定及发酵条件优化

背景]由有害木层孔菌(Phellinus noxius Corner)侵染引起的橡胶树褐根病是严重危害橡胶树的一类病害,给橡胶产业造成巨大的经济损失。目的]从橡胶树根际土壤中筛选对橡胶树褐根病菌具有高拮抗活性的放线菌菌株,为该病害生防药剂的研发提供基础。方法]采用稀释涂布法分离放线菌,平板对峙法、抑制菌丝生长速率法筛选拮抗菌株,通过培养特征、生理生化特征及16S rRNA基因序列分析确定其分类地位;利用单因子试验和正交试验相结合确定其最优发酵配方及培养条件。结果]筛选到一株对橡胶褐根病具有较强抑制作用的放线菌菌株17-7,其对橡胶树上的5种病原菌均有较好的抑制作用。菌株17-7与桑树链霉菌(Streptomyces samsunensi)亲缘关系较近,且形态特征、培养特征和生理生化特征基本相符。该菌株最优发酵配方和培养条件分别为:葡萄糖20.0 g/L、大豆粉25.0g/L、KH2PO4 1.0g/L、NaCl 0.5 g/L、CaCO30.5g/L,培养基装瓶量为150 mL/500 mL,起始pH 8.0,摇瓶培养转速为140 r/min,接种量为10%,培养温度为28℃,培养时间为5 d。结论]菌株17-7被鉴定为桑树链霉菌(Streptomyces samsunensi),其对橡胶褐根病具有较强的拮抗作用。

Screening, identification and fermentation optimization of an antimicrobial actinomycete strain 17-7 to Phellinus noxius

Background] Rubber brown root disease, caused by Phellinus noxius Corner, was a disease causing severely damage to rubber trees and huge economic losses in rubber industry. Objective] To isolate and screen antimicrobial actinomycetes strains with inhibitory activity on Phellinus noxius from the rhizosphere soil of rubber tree. Methods] The method of dilution plate coating was applied to isolate actinomycetes; The methods of growth plate-confrontation and mycelia growth inhibition were used to screen antimicrobial actinomycetes. Strain 17-7 was identified based on morphological, physiological, biochemical characteristics and 16S rRNA gene sequence. The conditions of fermentation and medium composition were optimized through single factor and orthogonal experiment. Results] Strain 17-7 showed antimicrobial activity to five plant pathogens of rubber trees. According to the results of morphological, physiological, biochemical characteristics and 16S rRNA gene sequence, strain 17-7 was identified as Streptomyces samsunensi. The optimum culture conditions of strain 17-7 were with a medium of glucose 20.0 g/L, soy powder 25.0 g/L, KH2PO4 1.0 g/L, NaCl 0.5 g/L, CaCO3 0.5 g/L, and liquid volume 150 mL in 500 mL flask, pH 8.0, rotation speed 140 r/min, inoculation amount 10%, culture temperature at 28 °C for 5 d. Conclusion] Strain 17-7 was identified as Streptomyces samsunensi and showed strongly inhibitory activity against Phellinus noxius.