高原土壤中稻瘟病拮抗细菌的抑菌效果及抗菌机理

Inhibition effects and antibacterial mechanism against rice blast of antagonistic bacteria in plateau soil

利用平板稀释法从西藏7个不同地点的土壤中分离筛选细菌,并通过平板对峙法对所分离菌株的稻瘟病菌抑制效果进行初筛,获得一株拮抗细菌YN01,对其进行生理生化和分子生物学鉴定、最适生长和发酵条件筛选,分泌IAA和铁载体能力检测及稻瘟病菌孢子抑制实验.经形态、生理生化特征和分子生物学鉴定,确定菌株YN01为萎缩芽孢杆菌(Bacillus atrophaeus).YN01对稻瘟病菌丝生长的抑制率超过90%,最适生长碳源、氮源分别为蔗糖和酵母粉,在pH值低于6时不能正常生长,最适生长温度为30-35℃;碳源及氮源分别为乳糖和谷氨酸、pH值为8以及培养温度为30-35℃时发酵液抑菌活性最强;YN01能够分泌IAA,浓度达到4.287 mg/L,同时能够产生铁载体,可溶性指数为1.72;与阴性对照相比,菌悬液和发酵液对稻瘟病菌的孢子萌发起到显著的抑制效果.拮抗菌菌体通过与病原菌丝进行营养和空间位点竞争以及产生有抑菌效应的代谢产物,从而导致稻瘟病菌的孢子萌发缓慢,菌丝发育停滞,扰乱其生理活动,达到抑菌目的.综上,拮抗细菌YN01具有较强的抑菌活性,是潜在的植物病原真菌生防菌资源,具有一定的开发与应用价值.

The aim of this study was to isolate antagonistic bacteria from the soil of seven different locations of Tibet. We tested with plate confrontation method the inhibitory activities of these bacteria against rice blast（Magnaporthe grisea） and obtained a strain of antagonistic bacterium named YN01. We also tested the physio-biochemical characteristics and molecular identification, and screened the best condition of growth and fermentation. We determined the IAA secretion ability with Salkowski colorimentric, and qualitatively detected the siderophores and spore inhibition effect with chromazurol S plate. Result based on physio-biochemical characteristics and molecular identification showed YN01 as Bacillus atrophaeus. The inhibition rate of rice blast mycelia exceeded 90%. Its best carbon source and nitrogen source were sucrose and yeast powder. The isolate could not grow normally when pH 6. The best temperature was 30-35 °C. The best condition of inhibition effect included sucrose, glutamate, pH = 8, and the best temperature region of 30-35 °C. YN01 had secretion abilities of IAA and siderophores. Contrasted with negative control, bacterial suspension and fermentation broth inhibited spore germination significantly. Through nutrition and spatial competition and produced metabolites, YN01 led to slacken spore of rice blast fungal germination, aberrant morphology in mycelia, and disrupted mycelia physiological activity. In summary, for its powerful bacteriostatic activity YN01 is a potential antagonistic bacteria source in the future.