萝卜软腐病生防菌株Hy11的筛选、鉴定及定殖特性

为探讨银杏内生细菌对萝卜软腐病的防病作用,通过块根接种和温室盆栽试验筛选对萝卜软腐菌Pectobacterium carotovorum subsp.carotovorum具有高效抑制作用的生防菌株,共获得8株拮抗作用较强的内生细菌,其中菌株Hy11抑菌作用明显.对生防菌株Hy11进行了形态观察、生理生化特性测定、16S rDNA和gyrB基因序列分析,并应用绿色荧光蛋白基因标记菌株Hy11,研究该菌株在萝卜体内的定殖动态.结果显示,该菌株对萝卜软腐病具有较好的防效,对萝卜块根和幼苗的防治效果分别为77.9％和66.7％；对萝卜幼苗的促生率达113.28％.经鉴定,菌株Hy11为解淀粉芽胞杆菌Bacillus amyloliquefaciens.标记菌株Hy11-gfp在喷雾接种银杏叶片后0～3 d种群数量呈急剧下降趋势,10d后保持相对稳定；其在萝卜的根、茎和叶中均能够定殖,在根中的定殖数量最高可达1.2×104 CFU/g.

Screening, identification of biocontrol bacterial strain Hy11 against white radish soft rot and its colonization characteristics

In order to study the biological control efficacy of the endophytic bacterial strains isolated from Ginkgo biloba leaves against Pectobacterium carotovorum subsp. carotovorum, the control efficiency of endophytic bacteria was screened using the tuber inoculation and pot expermient in green house. The results revealed that 8 bacterial isolates showed strong inhibitory activity, among which strain Hy11 suppressed the growth of the pathogen significantly. The strain Hy11 was identified according to the morphological, physiological, biochemical characteristics, analysis result of 16S rDNA and gyrB gene sequences. Meanwhile, the strain Hy11 was labeled with green fluorescent protein gene to investigate its colonization in white radish. The results revealed that the strain Hy11 performed good control potential against white radish soft rot disease with 77.9% control efficiency in tubers expermient and 66.7% in pot expermient, respectively. The strain Hy11 was also found to promote white radish seedlings growth remarkably with 113.28% growth-promoting effect. The strain Hy11 was identified as Bacillus amyloliquefaciens. The population of strain Hy11-gfp in leaves of G.biloba decreased sharply in the first 3 days after spraying and remained constant level after the 10th day. The strain Hy11-gfp could colonize in root,stem and leaves of white radish seedlings. The colonization amount of the strain Hy11-gfp could reach to 1.2×10⁴ CFU/g in white radish root.