茄子青枯病拮抗放线菌XL-6的筛选、鉴定及发酵条件优化

【背景】茄子青枯病是一种毁灭性的土传病害,生产上化学农药无法对其有效防治。拮抗放线菌具有环保、无残留的优点,并已在植物多种病害上成功应用,这为茄子青枯病的生物防治提供了思路。【目的】从健康茄子根际分离获得对茄子青枯菌有显著拮抗作用的放线菌菌株。【方法】采用稀释涂布法分离放线菌;采用双层琼脂法、琼脂扩散法和平板对峙法筛选拮抗菌株;对目标菌株XL-6的形态、培养特征、生理生化特征及16S rRNA基因序列进行综合分析;通过单因素试验和正交设计试验优化目标菌株培养基组分及发酵条件。【结果】筛选得到一株对青枯菌有强抑制作用的放线菌菌株XL-6,它对其他3种病原菌均具有一定的抑制作用。菌株XL-6的形态和培养特征、生理生化特征与娄彻氏链霉菌相符,而且16S rRNA基因序列分析表明该菌株与娄彻氏链霉菌亲缘关系较近。该菌株最优发酵配方和培养条件分别为:玉米粉30.0 g/L、酵母粉5.0 g/L、K_2HPO_4 2.0 g/L、MgCl_2 2.0 g/L和NaCl 1.0 g/L;初始pH 7.0、培养基装瓶量70 mL/250 mL、摇床转速180 r/min、接种量6%,在28°C条件下培养6 d。【结论】菌株XL-6经鉴定为娄彻氏链霉菌,优化其发酵条件后对青枯菌具有更强的拮抗效果。

Screening, identification and fermentation optimization of an antagonistic actinomycete strain XL-6 against Ralstonia solanacearum

Background] Bacterial wilt was a destructive soil borne disease without effective chemical pesticides to prevent. While antagonistic actinomycetes had many successful application on a variety of plant disease with environmental protection and no residual, which provided a new way for the biological control of bacterial wilt in eggplant. Objective] We isolate and screen antagonistic actinomycetes strains with inhibitory activity on Ralstonia solanacearum from the rhizosphere soil of healthy eggplants. Methods] Actinomycete was isolated by Pour Plate method. Antagonistic actinomycete was screened by double agar layer plaque technique, agar diffusion assay and confrontation culture in vitro. Strain XL-6 was identified by morphological, culture, physiological and biochemical characteristics and 16S rRNA gene sequence analysis. The fermentation condition was optimized by single factor and orthogonal experiment. Results] Strain XL-6 showed antagonistic to Ralstonia solanacearum and three other pathogens. Strain XL-6 belonged to Streptomyces rochei. The optimum culture conditions of strain XL-6 was with a medium of 30.0 g cornmeal, 5.0 g yeast powder, 2.0 g K2HPO4, 2.0 g MgCl2, 1.0 g NaCl in 1 000 mL filtrate water at initial pH of 7.0, liquid volume 70 ml in 250 ml flask, 180 r/min at 28 °C, inoculation size of 6% for 6 d. Conclusion] Strain XL-6 was identified as Streptomyces rochei and showed stronger antagonistic action to Ralstonia solanacearum under optimized fermentation conditions.