枯草芽孢杆菌（Bacillus subtilis）S9对植物病原真菌的溶菌作用

本研究共分离了976株细菌分离物，发现来自甘蔗根围的1株枯草芽孢杆菌(Bacillus subtilis)S9对立枯丝核菌(Rhizoctonia solani)、终极腐霉(Pythium ultimum)和西瓜枯萎病菌(Fusarium oxysporum f.sp.niveum)在PDA平板的对峙培养过程中不形成抑菌圈，但4d后可使上述植物病原真菌的菌丝溶解。扫描电镜观察发现S9菌株在待测的立枯丝核菌表面形成了溶菌斑。S9菌株对立枯丝核菌的作用过程是通过吸附在病原真菌的菌丝上，并随菌丝生长而生长，而后产生溶菌物质消解菌丝体。液体共培养测定也证明了S9菌株具有上述作用。本研究还发现，S9菌株对植物病原真菌的拮抗真菌绿色木霉(Trichoderma viride)、鲜红毛壳菌(Chaetomium cupreum)和球毛壳菌（Chaetomium globosum）的生长没有影响。盆栽试验证明了S9菌株可有效地控制立枯丝核菌(R．solani)引起的番茄苗期病害。S9菌株与其它拮抗真菌混合具有促进防治植物病原真菌引起的植物病害的潜力。

Cell-lytic effect of Bacillus subtilis on plant fungal pathogens

Nine hundred and seventy-sir bacterial isolates were obtained in this study, among which a bacterial antagonistic isolate, Bacillus subtilis S9 from sugarcane rhizosphere showed cell-lytic det on the plant pathogens, Rhizoctonia solani, Pythium ultimum and Fusarium oxysporum f. sp. niveum after 4-day-confronting incubation on PDA plates. However, S9 could not cause obvious inhibitory zones on PDA plates during this incubation. Lytic spots of hyphae of R. solani caused by S9 were clearly presented under scanning electronic microscope. The cell-lytic process of S9 is as follow: Bacterial cells of S9 absorb on hypae of R. solani firstly, and grow and reproduce as the fungal hrphae grow, and then secrete some cell-lytic substances to decompose the hyphae. However, this study revealed that S9 hardly interfered with the growth of the fungal antagonists, such as Trichoderma viride, Chaetomium cupreum and Chaetomium globosum. Pot experiments proved that S9 could effectively control root disease of tomato caused by R. solani. It suggested tha S9 mixed with above fungal antagonists could potentially synergistically control plant diseases caused by pathogenic fungi.