[Objectivc] It is aimed to screen cndophytic bacteria with high control effect on melon powdery mildew from the high-resistant melon varieties, in order to find a new way for biological control of melon powdery mildew. [Method] Pot and leaf disc experiments were used to screen the endophytic bacteria with better control effect on powdery mildew, and the strain with the best effect was identified with morphological, physiological, biochemical and molecular methods. [Result] Thirty-one strains of endophytic bacteria were isolated from the host ‘MR-1' with high resistance to powdery mildew Sphaerotheca fuliginea. Among them, the control efficacy of strain Mg15 was 74.3％ in the pot experiments. Besides, only 9.29％ of the spores were germinated after 12 hours in thc leaf disc experiments, while the production of conldia was decreased by 60％ after 14 days, compared with the control. The hyphae shrank and even deformed after application of Mg15 fermentation broth, observed by scanning electron micrograph. Additionally, application of Mg15 undiluted fermentation broth had the highest control efficacy on powdery mildew, with 80.66％ melon seedlings uninfected in a greenhouse experiment. [Conclusion] Mg15 showed better efficacy to melon powdery mildew, which was identified as Bacillus subtilis according to biological characteristics and 16S rDNA sequence.%[目的]从高抗白粉病的甜瓜品种植株内分离筛选出对甜瓜白粉病有较好防效的内生拮杭细菌菌株,为甜瓜白粉病生物防治探寻新途径.[方法]采用温室盆栽试验和叶盘漂浮法分离筛选有较好防效的内生拮杭菌,并对其进行形态学、生理生化和分子生物学鉴定.[结果]从高抗白粉病的甜瓜品种'MR-1'植株内分离获得31株内生细菌,其中1株内生菌Mg15对甜瓜白粉病盆栽试验防效达到74.3%.在离体叶盘上,经Mg15发酵液处理12h后白粉菌孢子萌发率仅为9.29%,14 d后产孢量与对照相比降低了60%.扫描电镜观察发现,Mg15发酵液处理后的病菌菌丝皱缩生长,甚至产生畸形.Mg15发酵原液温室防病效果达80.66%.[结论]Mg15对甜瓜白粉病具有显著防治效果,经鉴定该菌株为枯草芽胞杆菌(Bacillus subtilis).
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