Identification And Fermentation Condition Optimization Of Antagonistic Actinomycetes FX-H-2 And Evaluation Of Its Biocontrol Effect

Actinomycetes is a kind of microorganism group that have rich resource,it can produce a variety of secondary metabolites.The antibiotics are the most widely used in the production practice.Streptomyces produces the most of antibiotics and has the most in-depth study at present.Wheat sharp eyespot and root rot are serious soil borne diseases in agricultural production in recent years,the damage degree and range are also slowly expanding.Before in the laboratory we isolated,screened and obtained an actinomycetes strain FX-H-2.The research identifies the strain systematically and determines its antimicrobial activity targeting pathogenic fungi of wheat sharp eyespot and root rot and so on,optimizes the liquid fermentation conditions,measures the activity of fermentation filtrate,also determines its prevention effect and defensive enzymes activity of wheat in greenhouse conditions.Follows are the main conclusions:1.The classification status identification of actinomyces.The strain FX-H-2 is identified by the morphological characteristics,physiological and biochemical feature and the 16SrDNA sequence analysis.The results show that the strain FX-H-2 is in line with streptomyces and the 16SrDNA sequence is 1395bp.The strain FX-H-2 has 99%homology with Streptomyces mutomycini by relevant sequence blast in GenBank database,and they have the closest genetic relationship in phylogenetic tree.Finally,the strain FX-H-2 is identified as the Streptomyces mutomycini.2.The determination of the antimicrobial activity of the strain FX-H-2.It has better inhibitory effect to Rhizoctonia cerealis and Bipolaris sorokiniana and so on by plate confrontation method.3.Optimization of liquid fermentation condition.The L9(3~4)orthogonal table is used to optimize liquid fermentation conditions of the strain FX-H-2,and the Rhizoctonia cerealis is the target fungi.Then the variance analysis and range analysis are used to acquire that the optimal culture conditions are fermentation time 7d,3/10 liquid medium volume ratio and temperature 28?.The fermentation filtrate has the best bacteriostatic effect against pathogenic bacteria under these conditions.4.Bacteriostatic activity determination of fermentation filtrate.Using mycelium growth rate method for determining the fermentation filtrate which has inhibitory activity to Rhizoctonia cerealis and Bipolaris sorokiniana.When the volume ratio is 1/50 of the fermentation filtrate and culture medium,the bacteriostatic rate is 54.47%and 64.10%respectively.More over the mycelial morphology has changes under the microscope:the color of the mycelium becomes darker,the mycelial cell membrane becomes shorter,and the terminal cell wall thickens and expands.5.Greenhouse pot experiment.Under the greenhouse condition,using the fermentation filtrate to deal with the wheat seeding,then inoculating the wheat sharp eyespot and root rot pathogens,the results indicate that the incidence rate reduces by 43.34%and 30%respectively.Simultaneously defense enzyme activity:POD,PAL,PPO,SOD,CAT and MDA content are measured under the treatment using fermentation filtrate and comparing with clear water.Comparing with the clear water control,the activities of five defense enzymes increase completely and the MDA content decrease with the fermentation filtrate of the strain FX-H-2in wheat.The activities of the two enzymes of POD and PPO increase rapidly,reaching the peak in the early stage,the activities of PAL,SOD,CAT increase and MDA content decrease slowly,reaching the peak in the later period.The results show that:the fermentation filtrate of FX-H-2 can activate the defense enzymes of wheat,they act together to induce wheat disease resistance.