内生细菌B504的鉴定及对黄瓜枯萎病的生防作用

B504是从黄瓜植株中分离到的内生细菌。平板对峙试验表明，该菌株对黄瓜枯萎病菌等10种植物病原真菌具有拮抗作用，对黄瓜枯萎病菌的生长抑制率达44.1%。该菌株造成黄瓜枯萎病菌的分生孢子畸形，形成泡状物，尔后细胞壁消解，引起细胞内含物外溢，明显影响孢子萌发。用B504对黄瓜种子进行催芽处理，对黄瓜苗期、成株期枯萎病的防治效果分别为54.0%和41.7%。B504的16S rDNA序列与枯草芽胞杆菌具有高度相似性。根据菌体形态、培养性状、生理生化特性及16S rDNA序列分析等指标，确定B504为枯草芽胞杆菌（Bacillus subtilis）。

Identification of the cucumber endobacterial strain B504 and its biocontrol effects against the cucumber wilt

The endobacterial strain B504 isolated from cucumber stem was antagonistic against Fusarium oxysporum f.sp.cucumerinum and other 9 plant fungal pathogens by means of dual-culture tests.Its growth inhibition rate against F.oxysporum f.sp.cucumerinum was 44.1%.Strain B504 could interfere with the germination of spores via inducing spore malformation,vesicles in the cell plasma and the leak of cytoplasmic components.The control efficacy to cucumber seedling and plant wilt was 54.0%and 41.7%,respectively,after the seeds were treated with the strain B504.The strain B504 was identified as Bacillus subtilis according to its morphology,physiological and biochemical characteristics and 16S rDNA sequence analysis.