Marine bacterium strain SH-27 was applied to soybean plants to investigate the colonization dynamics, growth promotion effect and the biological control effect on Phytophthora root rot disease. Mutant strain SH-27Rif with stable marker of antibiotic rifampicin and inhibitory effect against Phytophthora sojae were screened by using the rifampin-resistant mutants and dual culture method. Colonizing dynamics of the strain SH-27Rif in root, stem and leaf of soybean were investigated by treating with root irrigating and leaf daubing. Then the effects of growth promotion and controlling disease on soybean seedlings were studied by pot tests. The results indicated that the resistance marker of the mutant strain SH-27Rif was remained stable after 10 generations of cultivation. The inhibition rates of strain SH-27Rif and original strain SH-27 against P. sojae were 56.92％ and 57.58％, respectively. The strain SH-27Rif could colonize for 31 days or more in soybean seedlings by root irrigating and leaf daubing. After root irrigating, the colonization quantity of strain SH-27Rif trended to increase firstly and then decrease. The highest quantity in roots was 6.6×105 cfu/g at 21 d after inoculation. Bacteria quantities in different parts were root>stem>leaf. After leaf daubing, the highest colonization quantity in leave was 6.3 × 105 cfu/g at 1 d after inoculation and then decreased quickly. Bacteria quantities in different parts were leaf>stem and strain SH-27Rif wasn't detected in root. Pot tests demonstrated that the height, root length, stem diameter, fresh weight, dry weight, chlorophyll and root activity of soybean seedlings treated with SH-27 fermentation broth were significantly higher than those of the control groups. When challenging the pathogen Phytophthora sojae, soybean seedlings treated by SH-27 showed decreased disease index significantly and the control efficacies were 83.44％, 66.34％, 57.18％ and 52.85％ at 3 d, 5 d, 7 d and 9 d, respectively. In conclusion, the results indicated that marine bacterium strain SH-27 was an excellent candidate for developing a biocontrol agent to control Phytophthora root rot of soybean.%为明确海洋细菌SH-27在大豆体内的定殖动态及其促生长作用和对大豆疫病的防治效果,本研究采用抗利福平标记法和平板对峙生长法,筛选对利福平标记稳定且对大豆疫霉菌具有较好抑菌作用的标记菌株SH-27Rif,培养10代后的标记菌株SH-27Rif能够保持稳定,对大豆疫霉抑制率为56.92％.分别采用灌根和涂叶法研究其在大豆体内的定殖动态,灌根与涂叶法均可使标记菌株SH-27Rif在大豆体内定殖,时间达31 d以上;灌根处理定殖量呈先升后降趋势,定殖量根>茎>叶,处理后第21 d根部定殖量达到最大(6.6×105 cfu/g);涂叶处理第1 d大豆叶片定殖量达到最大(6.3×105 cfu/g),随后呈迅速下降趋势;定殖量叶>茎,根部未检测到标记菌株SH-27Rif.盆栽促生试验结果表明,菌株SH-27发酵液灌根处理第15 d,处理组株高、根长、茎粗、鲜重、干重、叶绿素含量、根系活力等指标均显著高于对照组.盆栽防病试验结果表明:菌株SH-27发酵液灌根处理能显著降低大豆疫病的病情指数,对大豆疫病3、5、7和9d的防效分别为83.44％、66.34％、57.18％和52.85％.以上研究结果表明海洋细菌SH-27是防治大豆疫病的潜在生防菌株,具有良好的开发和应用价值.
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