Screening And Application Of Bacillus Subtilis X2 Strain

The method of soil dilution was used to analysis the relationship of defferent microorganism in saline soil in Daqing. The bio-control strain of bacterium X2 was isolated by means of using separated bacillus strains in dual culture with Sclerotina Sclerotiorum(Lib.)de Bary and Fusarium solani and determining the effect of different strain on the inhibition of mycelial growth and spore sprouting. According to physiological and biochemical identification and 16S rDNA sequence alignment, The strain X2 was identified as Bacillus subtilis.By measeuring the sustained of X2 strains and inhibition mycelial growth on Sclerotina Sclerotiorum(Lib.)de Bary, the best carbon sources, nitrogen sources, mineral and culture conditions were selected. The optimum for antibacterial substances produced of X2 was taken beef extraction 3g/L , NaCl 5g/L , Peptone 10g/L , Glucose 3g/L,FeSO4 0.01g/L and MgSO40.2g/L as medium, cultivated at initially pH 7.0～8.0, loaded apparently 50～100mL liquid volume in 250mL flask, shaked at 150～175 /rmin, incubated temperature 31℃for 48hs. Through the inhibition on the rate of mycelial growth, X2 sterile filtered fermentation had a high ability. After heat treatment at 121℃and eliminate its protein in fermentation decreased its inhibition activity. Within the range of pH 5.5～10, the inhibition activity was stabile. In vitro experiment, the ability of X2 strain on delaying soybean inoculated detached infection in leaves of soybean Sclerotinia sclerotiorum was proved.The growth conditions of plants were measured after appling X2 strain, solubilizing bacteria, potassium bacteria into the potting soil and measured the PAL, POD and PPO activity in roots of soybean, first leaf, third compound leaf after inoculating Sclerotina Sclerotiorum(Lib.)de Bary mycelium on fourth compound leaf for 24hs. The results showed that the soybean plant height, nodule number and plant dry weight were higher than control after appling supplied bacteria. The PAL activity, POD activity and PPO activity on roots of soybean plants and different lesves were changed, X2 strain had the ability to improve the plant defense enzyme activity. In soybean flowering stage, separated and measured the soil microorganisms, determined the soil enzyme activity, the result showed that the number of fungi in the soil decreased, the number of bacteria changed insignificantly, the number of actinomycetes increased. Appling phosphorus bacteria, potassium strains and X2 strain, the cellulase activity was no significant changed, Glucanase activity in the soil were increased significantly, phosphatase and urease activity was greatly improved with the same trend.