一株当归根腐病拮抗菌株的筛选、鉴定及培养条件优化

Screening,identification and optimization of culture conditions of an antagonistic strain to Angelic sinensis root rot

本研究从河西走廊盐碱土中分离得到的多株对植物病原菌具有拮抗活性的细菌菌株中,筛选当归根腐病拮抗菌株,为当归根腐病的生物防治提供适合的菌种资源.采用平板对峙、琼脂扩散法筛选拮抗细菌,通过形态学、生理生化试验及分子生物学鉴定法确定菌株分类学地位;以活性物质稳定性试验为基础,设计单因素试验,响应面分析法优化培养条件.结果表明:菌株A17-2-1具有较好的当归根腐病拮抗活性,且抗菌谱较广,经鉴定为贝莱斯芽孢杆菌(Bacillus velezensis);其活性物质在高温、强碱及紫外照射下均具有较好的稳定性;最优培养条件为pH8.5、温度32℃、氯化钠含量0.5%,在此条件下培养24 h,菌株A17-2-1菌悬液在波长600 nm处吸光度值为1.360,且在该条件下对两株当归根腐病病原菌的抑菌率均达到81.01%以上.

In this study,we propose to screen Angelic(A.)sinensis root rot antagonistic bacteria from multiple strains of bacteria isolated in the saline-alkali soil of Hexi corridor in the early stage of the research group,and provide suitable strain resources for the biological control of A.sinensis root rot.Plate confrontation and agar diffusion method were used to screen antagonistic bacteria,and the taxonomic status of strains was determined by morphological,physiological and biochemical tests and molecular biology identification methods.Based on the stability test of the active substance,the single-factor experiment was designed,and the response surface analysis method was used to optimize the culture conditions.The results showed that strain A17-2-1 has good antagonistic activity of A.sinensis root rot and a wide antibacterial spectrum,and is identified as Bacillus velezensis.Its active substances have good stability under high temperature,alkali and ultraviolet radiation.The optimal culture conditions are pH 8.5,temperature 32℃,sodium chloride content of 0.5%.Under these conditions,the absorbance value of bacterial suspension of strain A17-2-1 at 600 nm is 1.360 after cultivation for 24 h,and the bacteriostatic rate of the two A.sinensis root rot pathogens under this condition can reach more than 81.01%.