Study On Antagonistic Bacillus F53 Inhibiting Verticillium Dahliae

In this paper, a strain of Bacillus sp. (F53) was obtained from eggplant rhizosphere by assessing the inhibition zone in vitro,which has proved strong inhibiting activity antagonistic to pathogen Verticillium dahliae. Our work involved with optimizing fermentation, studying the stability of fermentation liquor and the property of the active substrate from fermentation liquor, probing the inhibiting mechanism, controlling infection test with eggplant plagued artifically with pathogen Verticillium dahliae. And then, preliminary identificating of the strain according to physiological and biochemical property and 16S rDNA analysis.The screening study demonstrated F53 has a strong plate inhibiting ability, chitinase and β-1, 3-glucanase can be acquired in solid fermentation, activity spectrum was wide because it can obviously inhibit the growth of many kinds of indicator strains.In order to optimize the fermentation, through orthogonal tests of carbon and nitrogen source and culture condition tests, we obtain a optimal medium composition(%): cance sugar 0.3, corn flour 0.3, peptone 1.0, soybean meal 0.3, NaCl 0.5, FeSO₄ 0.002 and MgSO₄ 0.04; and the optimal culture conditions are: initial pH7.0⁸.0, inoculation level 4%, a 150 r/min shake revolutions with 50ml medium in 250ml flask, culture temperature 34℃ and culture time 48 hours, which provided a theory reference for enlarging test in fermenter.The study of fermentation liquor indicated that it has a good thermal, sour and alkali, protease and storage stability. The inhibiting ability was not changed a lot after fermentation liquor boiled at 100℃ for 100 minutes,layed for 48 hours in the condition of pH 3.0¹0.0, treated with protease K and trypsin for some time and conserved for 6 months at 4℃.Different degree of saturation of (NH₄)₂SO₄ saltingout the fermentation liquor resulted that the inhibition zone of crude protein antagonistic to pathogen Verticilliumdanliae is the best when the degree of saturation is 70%. We can not measure chitinase activity from the fermentation liquor, and the 0-1, 3-glucanase activity doesn't need inducement.The study of inhibiting mechanism demonstrated that the fermentation liquor can inhibit the hyphal's growth and spore's sprouting of pathogen Verticillium dahliae. The pot culture experiment of eggplant seedling with pathogen verticillium dahliae in the greenhouse suggested that the controlling efficiency of the strain can reach 46.3-75.8%.According to morphological characteristic, plate cultural characteristic, physiological and biochemical property and 16S rDNA analysis, strain F53 was preliminary identified to be Paenibacillus.