Preliminarily Study On Screening,Fermentation And The Metabolite Of Soil Actinomycetes LH33-3

This research aimed at screening of antagonistic actinomycetes with great activity to plant pathogens,identifying the antagonistic strain,optimizing the fermentation medium and conditions,studying and analyzing the actinomyctes substances produced by them preliminarily to searching for the source of new agri- antibiotics.In the experiment, 198 strains of actinomyctes were isolated from two soil samples. By plate decussation test and cell-free fermentation filtrate screening ,LH33 was obtained which is a stronger antagonistic actinomycetes and can inhibit Pyricularia oryzae, Alternaria solani ,Botrytis cinerea, Venturia nashicola, Gaeumannomyces graminis, Exserohilum turcicum , Fusarium graminearum and Phomopsis vexans.The screening of single-spore inhibiting activity showed that the inhibiting activity of LH33-3 was the best,the inhibition rate on Pyricularia oryzae and Gaeumannomyces graminis were better,could reach 90.5% and 88.4% respectively.At last,the strain LH3-3 was the best strain.Based on morphological,cultural,and physiological-biochemical characteristics of the strain LH33-3, it was regarded as Streptomyces Gyaneus aureofaciens preliminarily. The optimum fermentation condition which can produce the most effective fermental filtrate and inhibitory effect is best was 72 hour for rotational culture time,pH 8.0 of medium,30℃, rotational velocity is 150r/min, volume of medium is 100ml, inoculationh volume is 10%.The crude active-product of LH33-3 has a wide-range of inhibition. 1mg/l materials has an inhibition efficiency above 45% against Pyricularia grisea,Fusarium graminearum, Gaeumannomyces graminis, Phomopsis Vexans, Botrytis cirerea,Exserohilum turcicum and Phytophthora capsici et al.Study on inhibiting mechanism of strain LH33-3 demonstrated that metabolites produced by antagonistic strain LH3-3 could strongly inhibit the sporus germination and mycelia growth.Oberserving by microscope showed that the mycelium inhibited by strain LH33-3 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. This strains of fermented extracts can inhibit spore germination of Alternaria solani strongly , the inhibition rate of the minimum concentration (1mg/L) of the liquid is 55% ,the deformiting rate is 38% .Results of pot experiment showed that cell-free fermentation filtrate of LH33-3 had strong preventing and cure efficacy on Botrytis cinerea, the preventing and cure effect could get to 94.2% and 80.4% respectively when fermentation filtrate is in 100mg/L concentration .In the greenhouse study, the strain can LH33-3 can appeared promoting effect on the tomato growth ,and the height of tomato increased 83.7% compared with CK , the growth promoting effect are all retain up to 80%.