Streptomyces sp. strain MBCN152-1, isolated from cabbage, has potential as a biocontrol agent for Alternaria brassicicola on cabbage seedlings. The present study examined its mode of action. Light microscopy showed that appressorium formation by A. brassicicola was significantly suppressed on cabbage seedlings bacterized with MBCN152-1. Furthermore, scanning electron microscopy revealed that the mycelia of MBCN152-1, which were epiphytically growing on the cotyledon leaves of cabbage seedlings, intensively coiled around the germinating conidia of A. brassicicola. In vitro co-culture experiments demonstrated that MBCN152-1 is an aggressive mycoparasite of A. brassicicola, but not of A. brassicae or Colletotrichum higginsianum. Biocontrol experiments indicated that MBCN152-1 did not control diseases caused by A. brassicae or C. higginsianum. These results suggest that mycoparasitism is the primary mode of action for MBCN152-1. This is the first study to clearly demonstrate the significance of mycoparasitism in the biocontrol efficacy of endophytic Streptomyces.

中文翻译：

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链霉菌属真菌寄生的意义。MBCN152-1 对链格孢菌的生物防治活性。

链霉菌属。从卷心菜中分离得到的菌株 MBCN152-1 具有作为卷心菜幼苗上十字纹孢菌的生物防治剂的潜力。本研究检查了其作用方式。光学显微镜显示，在用 MBCN152-1 菌化的卷心菜幼苗上，A. brasicola 的附着胞形成受到显着抑制。此外，扫描电镜显示MBCN152-1的菌丝体附生生长在甘蓝幼苗的子叶上，密集盘绕在A. brasicicola的发芽分生孢子周围。体外共培养实验表明，MBCN152-1 是 A. brasicicola 的侵袭性真菌寄生虫，但不是 A. brasicae 或 Colletotrichum higginsianum 的侵袭性真菌寄生虫。生物防治实验表明 MBCN152-1 不能控制由 A. brasicae 或 C. higginsianum 引起的疾病。这些结果表明，真菌寄生是 MBCN152-1 的主要作用方式。这是第一项清楚地证明菌寄生在内生链霉菌生物防治功效中的重要性的研究。