Optimization Of Spore-forming Conditions Of Bacillus Subtilis BIB-9 And Its Effect On Tomato Growth

Soil microbes are closely related to plant growth,and microbes play a key role in plant disease prevention and disease resistance.The strain BIB-9 is a biocontrol bacteria preserved in the laboratory,has a high sporulation rate,and has four pathogenic fungi(Fusarium proliferatum,Fusarium solani,Fusarium oxysporum).And Fusarium moniliforme Sheld)has broad-spectrum resistance and has potential as a biocontrol agent.Therefore,the morphological observation,physiological,biochemical and molecular identification of the strain were carried out,and the antibacterial activity of the strain BIB-9 was explored.The conditions of spore fermentation were optimized,and the potential of growth and biocontrol was tested by tomato pot experiment,which provided experimental basis for the production and application of the strain.The medium of strain BIB-9 was optimized,and the optimal carbon source of BIB-9 was determined to be corn flour by single factor experiment.The optimal nitrogen source was soybean powder.The inorganic salt is calcium chloride;the optimal medium formula is determined by the response surface test.The optimal medium component of the strain BIB-9is 27.8g/L soybean powder,corn flour 30g/L,Ca Cl2 2.01g/L.,the temperature is 38.34?,the shaking speed is 220 rpm,the inoculum volume is 3%,the liquid volume is 80 m L/250 m L,the initial p H is 7.5,the fermentation period is 36 h,and the sample is allowed to stand for 12 h.The obtained fermentation broth of the strain BIB-9 has the most spore production ability.Strong,the spore concentration was 4.22×109cfu/m L,which was 75.8% higher than the preoptimized spore concentration.The effect of strain BIB-9 on the growth of tomato was studied by pot experiment.The strain BIB-9 was prepared as a microbial agent and organic fertilizer.The results showed that compared with the control group(CK),liquid microbial treatment(T1)and solid microbial treatment(T2)can significantly increase the plant height of tomato plants.,ground diameter,fresh weight and dry weight,T1 increased by 103.34%,69.48%,247.4% and 173.47%compared with CK,T2 increased by 61.92%,52.42%,118.85% and 123.32% compared with CK;can significantly increase the content of chlorophyll a,chlorophyll b and carotenoids,T1 increased by 47.31%,81.82% and 32.5% compared with CK,T2 increased by 34.4%,66.67%and 22.5% compared with CK;can be significant the activities of superoxide dismutase,peroxidase and catalase in tomato roots were increased.T1 increased by 41.19%,260% and 61.55% compared with CK,T2 increased by 26.15%,160% and 90.93% compared with CK;can significantly reduce the content of malondialdehyde,compared with CK,T1 and T2 decreased by 54.41% and 54.49%;can significantly increase the active surface of invertase,catalase and urease in soil,T1 increased by 35.12%,19.44% and 62.50% compared with CK;T2 increased by 8.25%,8.33%,and 50% compared with CK.Compared with the fermentation substrate treatment,there was a significant difference between T1 and T2,which proved that the strain BIB-9 had good biocontrol potential.