油菜菌核病内生拮抗细菌的筛选及防病作用研究

以油菜菌核病菌Sclerotinia sclerotiorum为靶标菌,测定了63株内生细菌对其菌丝生长、菌核形成及萌发的抑制作用。结果表明:在所有供试菌株中,除1株未表现出抑菌活性外,其余菌株均有抑菌作用,其中有6.3％的菌株抑菌带大于10 mm,7株细菌可完全抑制病原菌的菌核形成,1株细菌可完全抑制菌核萌发;此外,结合生物测定结果,从中筛选到1株对油菜菌核病的高效生防菌株Em7,其无菌培养滤液对温室苗期油菜菌核病的防治效果可达97.5％。通过形态特征、生理生化特性及16S rDNA序列分析,认为该菌株属于枯草芽孢杆菌Bacillus subtilis。于接种病菌前后不同时间喷施菌株Em7无菌培养滤液,对油菜菌核病均有防治效果,但防效之间差异显著,以接种病菌前24 h喷施防效最高。原液及不同稀释度无菌培养滤液对菌丝生长、菌核萌发及病害防治的效果明显不同,随着稀释度的增加,其抑菌效果降低。显微观察结果表明,菌株Em7对油菜菌核病菌菌丝的生长与发育会产生明显影响,可致使菌丝畸形、皱缩及细胞质外渗。

Screening of antagonistic endophytic bacteria and their roles incontrol of Sclerotinia sclerotiorum in canola

The antagonisms of 63 endophytic bacteria strains isolated from wheat on Sclerotinia sclerotiorum were detected in vitro and in greenhouse.The results showed that 62 strains exhibited antifungal activities against S.sclerotiorum.Among them,6.3％ strains of endophytic bacteria could highly inhibit S.sclerotiorum with inhibition zone more than 10 mm.Seven strains could completely inhibit the formation of sclerotia,and one strain could completely inhibit the germination of sclerotia.In addition,strain Em7 showed strong inhibition to the mycelial growth,sclerotia formation and germination of S.sclerotiorum in vitro.And the biocontrol efficacies of cell-free cultural supernatant of Em7 was 97.5% on Sclerotinia stem rot of canola seedling in greenhouse.According to the morphological,physiological,biochemical characteristics and 16S rDNA sequence,strain Em7 was identified as Bacillus subtilis.The biocontrol efficacy was different when spay the cell free culturel filtrate of Em7 before and after inoculation of S.sclerotiorum.Spaying cell free supernatant 24 h before inoculation of S.sclerotiorum presented the highest control efficacy.Different dilution factor of cell free supernatant showed different inhibitory effects on S.sclerotiorum both in vitro and in vivo.With increasing dilution factor,the inhibition rates to mycelail growth and sclerotia germination decreased,and the biocontrol efficacies declined.Strain Em7 induced alterations on hyphae morphology of S.sclerotiorum,such as leakage,cytoplasm exosmosis and deformation.