Preliminarily Study On Isolation, Screening And Fermentation Of Antagonistic Bacillus From Soil

Bacillus is a crowd of like oxygen or tires of the oxygen, produces spore,Gram-positive bacteria,which many types, big quantity, distribution extremely wides pread, its physiological characteristic is bountiful, is the important microorganism population in soil and plant body surface rhizo sphere. Because of Bacillus has the spore, have strong resistance, the quick speed reproduction, the nutrition requestis simple and easy breed in the plant root periphery characteristic, so it research and use widely in plant disease biology preventing and controlling.This research aimed at isolating and screening of antagonistic bacillus from soil with great ability to suppress kinds of plant disease, identifying the antagonistic strain,optimizing the fermentation medium and conditions,studying the inhibitory efficacy,searching for new resources for plant disease biological control.In the experiment, 142 strains of Bacillus were isolated from soil samples,heated at 80℃for 10 min.By plate test and cell-free fermentation filtrate screening,B-Q2 was obtained which is a stronger antagonistic bacillus and can inhibit Magnaporthe grisea,Fusarium graminearu m, Fusarium oxysporum,Venturia nashicola,Alternaria alternate and Botrytis cinerea.The screening of single-spore inhibiting activity showed that the inhibiting activity of B-Q2-7 was the best,the inhibition rate on Magnaporthe grisea and Botrytis cinerea were better,could reach 87.4% and 91.6% respectively.At last,the strain B-Q2-7 was the best strain.Based on morphological,cultural,and physiological-biochemical characteristics of the strain B-Q2-7, it was regarded as Bacillus licheniformis preliminarily.Results of pot experiment showed that cell-free fermentation filtrate of B-Q2-7 had strong preventing and cure efficacy on Botrytis cinerea,the preventing and cure effect could get to 89.6% and 80.4% respectively when fermentation filtrate was diluted 10 times, they are more than 60% when fermentation filtrate was diluted 250 times.The optimum fermentation medium of B-Q2-7 was screened by single factor test and orthogonal design experiments, and it was composed of D-glucose 1.2%, surcose 0.6%,starch 1.2%,soybean flour 3%,Yeast paste 0.3%,K2HPO4 0.2%.The optimum fermentation condition which can produce the most effective fermental filtrate and inhibitory effect is best was 36 hour for rotational culture time,pH 8.0 of medium,36℃,rotational velocity is 150r/min.Study on inhibiting mechanism of strain B-Q2-7 demonstrated that metabolites produced by antagonistic strain B-Q2-7 could strongly inhibit the sporus germination and mycelia growth.Oberserving by microscope showed that the mycelium inhibited by strainB-Q2-7 mostly twisted,inflated,deformed, the abnormal branching increased, the mycelia wall broke and formed expanded vacuole. The rate of germination and length of the tube was decreased. It's germination inhibition rate of Venturia nashicola and Botrytis cinerea could reach 95.9% and 100% when fermentation filtrate was diluted 10 times.