为了寻找对烟草黑胫病具有生防潜力的放线菌，笔者采用平板对峙法，从烟草黑胫病发病烟田健株根际土壤中，分离得到1株对烟草黑胫病菌具有显著拮抗效果的放线菌株LY18，其发酵液的无菌滤液对烟草黑胫病菌菌丝的抑制率达70%以上。电镜观察发现，抑菌圈周围的烟草黑胫病菌丝破裂、瘪陷。通过对LY18的形态观察、培养性状观察、生理生化测定结合16S rDNA序列分析，将该菌株为鉴定Streptomyces rajshahiensis。

In order to screen antagonists against Phytophthora parasitica var. nicotianae, the plate-confrontation method was used. Actinomycetes strain LY18 isolated from soil samples around healthy tobacco individuals’ roots in tobacco field which broke out tobacco black shank, showed well inhibitory activity to Phytophthora parasitica var. nicotianae. The aseptic filtrate of LY18 mixed into medium plate against Phytophthora parasitica var. nicotianae by reducing mycelium growth 70%. The mycelium of Phytophthora parasitica var. nicotianae in plate added aseptic filtrate of LY18 was degradation by SEM observed. LY18 was identified as Streptomyces rajshahiensis according to its morphology, culture characteristic, chemotaxonomic tests and 16S rDNA analisis.