| The compounds of antifungal substance and biosurfactant character produced by Baclillus subtilis B1 and B2 were studied in this paper. At the same time, the control efficacy of B1 and B2 against root rot of DangGui and HuangQi as well as powdery mildew of cucumber was tested in field. The results were as follows: 1. Purification and identification of the antifungal substances from B1, B2. (1) Both of the whole cell culture filtrate and cell free filtrate of B1and B2 had the inhibition activity against fungi, while cell suspension hadn't. Moreover,we found AFVs(antifungal volatiles)were produced by B1, and the inhibitory rate of AVFs against R.solani was 28.43%. (2) Liquid cultures of B1,B2 were precipitated by acidification to pH2, the active fraction was extracted from the precipitate with ethyl ether and was dried at 40℃on a rotary evaporator. The compounds in the extract were separated by thin-layer chromatography using methano: chloroform: water (64:25:1) as the developing solvent. Detection of the antifungal compound was done by bioassay with spores of Fulvia fulva. Two inhibition bands were detected from B1, B2 cultivar, respectively: RF=0.79, RF=0.28, RF=0.75, RF=0.24.Color reactions and LC-MS analysis indicated that antifungal substances produced by B1, B2 were lipopetide surfactin. 2. The character and composition of surface active substance produced by B1, B2 When fermented broth of B1and B2 were treated at 20 ℃~ 110℃for 2h, the surface tension of them were 28.34~30.12 and 28.34~31.53 dyne/cm, respectively; the surface tension of them were 27.07~28.42 dyne/cm and 28.98~30.9 dyne/cm when the pH value varied in range 2.0~7.0; while the treated conditions of salinity (NaCl mass concentration) raised from 2.0×10~4 to 2.0×10~5mg/L, the surface tension of them were 27.45~30.88 dyne/cm and 29.02 ~36.97 dyne/cm, respectively. The results showed the surface active substance produced by B1and B2 had high endurance to heat, salt and acid. When the surface active substance concentrations of B1 and B2 were 0.03 g/L, 0.04 g/L and 0.05 g/L, the inhibitory rates of surface active substance against Rhizoctonia solani were 19.29%,28.71%,45.65% and 20.14%,30.82%,57.18%, respectively. All of these indicated that the surface active substance produced by B1and B2 inhibited the mycelial growth of R.solani significantly. Using IR and TLC analysis methods, the surface active substances extracted from fermented broth of B1and B2 were identified as lipopeptide. 3. Study on the disease-prevention and growth-promotion of B1, B2 in field. In field experiments, B1and B2 could not only promote growth of DangGui and HuangQi, but also control the root rot of them. The control efficacy on root rot of DangGui and HuangQi with B1 was up to 39.13%and 41.48% ,respectively; B2 was up to 41.30% and 48.16%,respectively.There was no significant difference between B2 and CK1.Meanwhile, the yields of DangGui and HuangQi were increased by B1 and B2, the yield increase rates of DangGui were up to 7.74% and 17.20% and HuangQi were up to 12.5%and 16.25%respectively. 4. Powdery mildew of cucumber was controlled by B1and B2. Different dilution times of B1 and B2 were chosen to decrease the damage caused by powdery mildew in cucumber. The experiment indicates that 10 times of dilution had the best control efficacy for powdery mildew of cucumber among the three treatments, the control efficacy of B1 and B2 could reach to 53.68% and 57.65%. The indoor experiment results showed that 10 times of dilution also was the best one to control the growth of spores, and the abnormality rates of spores got to 34.6% and 43% after the spores were treated by 10 times of dilution. |
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