Biocontrol activity of an endophytic Streptomyces sp. strain MBCN152-1 and its mode of action

通过扫描电镜观察，发现链霉菌MBCN152-1在白菜子叶角质层表面和细胞间隙定植。光镜和荧光显微镜观察表明，MBCN152-1能将芸苔菌与其他真菌区分开来，并能寄生于芸苔菌菌丝细胞壁。但有趣的是，MBCN152-1对草莓炭疽病病原菌——非宿主病原菌带状肾小球（Glomerella cingulata）表现出较强的生物防治效果。将MBCN152-1定殖的白菜幼苗接种甘蓝芽孢杆菌后，虽然在被侵染菌丝穿透的细胞中未观察到形成乳头等物理屏障，但其侵染效果明显受到抑制。这些结果表明，菌株MBCN152-1的生物防治机制涉及寄主植物细胞的分枝寄生和诱导系统抗性，而不形成物理屏障。

By scanning electron microscopy, it was revealed that Streptomyces sp. strain MBCN152-1 colonized cuticle surface and intercellular spaces of cabbage cotyledons. Light and fluorescent microscopic observation indicated that MBCN152-1 could discern A. brassicicola from other fungi, and parasitize hyphal cell wall of A. brassicicola. However, interestingly, MBCN152-1 exhibited intensive biocontrol effect against non-host pathogen Glomerella cingulata, causal agent of strawberry anthracnose. When cabbage seedlings colonized by MBCN152-1 were inoculated with A. brassicicola, infection by the pathogen was significantly suppressed, though formation of physical barrier such as papillae was not observed in the cells which were penetrated by infection hyphae of the pathogen. These results suggested that mycoparasitism and induction of systemic resistance without formation of physical barrier in the host plant cells were involved in the mechanisms of biocontrol by strain MBCN152-1.