枯草芽孢杆菌（Bacillus subtilis）B931是分离自小麦田的植物病害生物防治细菌，对多种作物土传病害都有很好的防治效果，并能促进作物生长。本研究通过转座子Tn917的转座诱变，构建了菌株B931的突变体库。自3 000多个突变体中，筛选得到了6个对小麦全蚀病菌抑制能力丧失的突变体（B931-A－），和多个产生长素、赤霉素、细胞分裂素能力增加的突变体B931-I+、B931-G+、B931-C+，以及产这3类激素能力减少的突变体B931-I－、B931-G－、B931-C－。温室测定这些突变体对小麦全蚀病及棉花立枯病的防治作用，结果表明抗生素的产生是B931具有病害防治能力的主要原因。产植物激素能力变化的突变体对苗期小麦和棉花没有促生长作用，但对甘薯苗的生根有显著的促进作用。
Bacillus subtilis B931, a biological control bacterium isolated from wheat field, protects plants against many soil-borne diseases and promotes plant growth. A mutant library of B931 containing over 3 000 Tn917 mutants was constructed by transposon mutagenesis with plasmid pTV1::Tn917. Six mutants defective in antibiotic production (B931-A－) were selected by dual culture test with Gaeumannomyces graminis var. tritici on PDA plates. Another six mutants which over-produced or less-produced phytohormones 3-Indoleacetic acid (IAA), gibberellin (GA3) or cytokinin (CTK), respectively, were selected by ELISA and HPLC methods. Greenhouse experiments showed that, compared with the wild type, the antibiotic-defective mutant was less effective in biological control of wheat take-all caused by G. graminis var. tritici and cotton damping-off caused by Rhizoctonia solani, indicating that the antibiotic production played a major role in the biocontrol activity of B931. The mutants that over-produced or less-produced phytohormones had no significant influence on seedling growth of wheat and cotton. However, the mutants that overproduced IAA or CTK could significantly promote root growth of sweet potato seedlings.
全 文 ：