Isolation, Screening And Identification Of Anti-fusarium Bacillus And Preliminary Study Of The Disease-suppressive Mechanisms

The study was aimed at a prominent problem that had perplexed people withcontrolling plant diseases of fungi for a long time. It was, started from biological control,projected to coordinate the contradiction between control efficiency, environment, foodsecurity and economy. Wide-ranging samples was sampled from different areas in ourprovince with soils and plant body; A number of common pathopoiesia Fusarium was usedas indicator; A series of work, including isolation，screening and identification, was putinto effect, and several valuable Bacillus was elected. Among them, Strain5-1andstrain36-3proved excellent disease-resistance. Strain5-1was researched for thepreliminary disease-suppressive mechanisms, which provided a good base for further study.Main results of the study was as follows.1There widely is various anti-Fusarium spore-bacteria in surroundings around plants,and by proper methods of isolation, screening, we may obtain prospective spore-bacteriawhich resist pathogenic Fusarium of plants.2The probability of isolating spore-bacteria from soil samples exceeded significantlythat from live samples, while the probability of screening anti-Fusarium spore-bacteriafrom live samples exceeded greatly that from soil samples.3By way of tests with inhibition zone, inhibition ratio and antibiogram,spore-bacteria strains with comprehensive advantages of marked inhibiting efficiencyand wide antibiogram, could be elected.4Selected strain5-1and strain36-3, through tests of morphology, physiology andbiochemistry, were preliminarily identified as Bacillus. Licheniformis and Bacillus.Pumilus respectively. The study of16SrDNA alignment indicated that strain5-1andstrain36-3were100%and99%similar with Bacillus. Licheniformis and Bacillus. Pumilusrespectively. Both of the results showed no difference.5Test of strains combination showed that the total inhibiting efficiency of strain5-1，strain36-3and their combination were all higher than the CK(Bacillus subtilis); the totalinhibiting efficiency of combination was well over strain5-1and strain36-3; However, inview of single indicator, inhibiting efficiency of strain5-1was number one.Pot culture test proved that strain5-1treatment and combination(strain5-1+strain36-3)treatment showed marked control efficiency(30.8%and29.2%,respectively)over Fusarium wilt of cotton. There was some complementary good effect in combination treatment.7Strain5-1inhibition mechanism:①It was a main antagonism form secreting solubleantagonistic active substance out of cell;②Antagonistic active substance resulted inpathogenic fungi shortening and widening branchs, breaking, dissolving and swellinghypha, so that normal hyphae growth was hampered, cell structure destroyed.③Activesubstance was susceptible to high temperature above100℃, but tolerant to lowertemperature bellow100℃, especially80℃. It was susceptible to pH value, especiallyhigher pH value. Limits with high activity was pH6.0~7.0. It was not susceptible to lightwhile was susceptible to ultraviolet. The activity came down obviously after6h ofirradiation under the test condition. It was susceptible to protease and the susceptibility wasmarkedly different between protease kinds.④Protein or polypeptide was the maincomponent of the antagonistic active substance.60%saturation of ammonium sulphatecould precipitate most antagonistic active substance.