黄瓜枯萎病拮抗放线菌的筛选、鉴定及发酵条件优化

【背景】黄瓜枯萎病是由尖孢镰刀菌(Fusarium oxysporum f. sp. cucumerinum)黄瓜专化型引起的土传真菌性病害,严重制约着黄瓜产业的发展。【目的】从河西走廊敦煌地区盐碱土壤中分离筛选出一株对黄瓜枯萎病病菌有良好拮抗效果的放线菌菌株,探究其分类地位及其最优发酵条件。【方法】采用稀释平板涂布法分离放线菌,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、生理生化试验及16SrRNA基因序列分析确定其分类地位,利用单因素试验和正交试验方法确定其最优发酵配方及培养条件。【结果】菌株16-3-10鉴定为链霉菌属(Streptomyces sp.)菌株,最优发酵配方(g/L):小米10.0,乳糖20.0,蛋白胨1.0,NaCl 5.0,CaCO3 6.0,最优发酵条件:培养温度28°C,装瓶量50/250 mL,培养3 d,起始pH 10.0,抑菌率达82.50%,比优化前增加153.43%。【结论】菌株16-3-10对黄瓜枯萎病病菌具有显著的拮抗效果,有较好的应用前景。

Screening, identification and optimization of fermentation conditions of an antagonistic actinomycetes to cucumber Fusarium wilt

Background] Cucumber Fusarium wilt is a soil-borne fungal disease caused by Fusarium oxysporum f. sp. cucumerinum, which seriously restricts the development of cucumber industry. Objective] Screening and identification antagonistic actinomycete strains with strongly inhibitory activity against Fusarium oxysporum f. sp. cucumerinum was isolated from saline-alkali soil in Hexi corridor. We identified the antagonistic actinomycete strain and optimized the fermentation conditions. Methods] The method of dilution plate coating was applied to isolate actinomycetes; The methods of growth plate-confrontation and speed rate were applied to screen antagonistic actinomycetes; The morphological characteristics, physiological and biochemical characteristics, and 16S rRNA gene sequence of strain 16-3-10 were analyzed the taxonomic status. The conditions of fermentation and medium composition were optimized through single factor and orthogonal experiment. Results] The result of identification revealed that strain 16-3-10 can be classified as Streptomyces sp., the optimum culture conditions of strain 16-3-10 were with a medium was as follows: millet 10.0 g/L, lactose 20.0 g/L, peptone 1.0 g/L, NaCl 5.0 g/L, CaCO3 6.0 g/L at 28 °C, liquid volume 50 mL in 250 mL flask, initial pH of 10.0 for 3 d, and inhibition rate of strain 16-3-10 to pathogen reached to 82.50% under this condition. Conclusion] The result indicates that 16-3-10, strongly inhibitory activity against Fusarium oxysporum f. sp. cucumerinum, might act as a potential candidate for the application.