Screening Of Antagonistic Actinomycetes And The Control Effect Of It's Bio-Organic Fertilizer On Tomato Bacterial Wilt

As a kind of devastating soil-borne disease in the world,tomato bacterial wilt caused a huge loss to the agricultural production in China.Therefore,it's urgent to explore the biological control measures that can effectively control tomato bacterial wilt.Biological control,as an effective measures to control plant diseases receives more and more attention in recent years.Actinomycetes as the main microbial sources of natural active substances and drugs,is widely used to control plant diseases.Many studies have shown that bio-organic fertilizers which is made by combination with antagonistic microbial and organic fertilizers are more effective in controlling soil-borne diseases than single antagonistic microbial agents.In this study,we isolated and screened an actinomycete strain with strong inhibitory effect on R.solanacearum ZJ3721 from tomato rhizosphere soil,identified the strain,optimized the fermentation conditions of the strain,and then prepared the actinomycete bio-organic fertilizer to verify its actual control effect on tomato bacterial wilt.The main findings are as follows:1.From the soil samples of tomato plantting,6 strains of antagonistic actinomycete against R.solanacearum ZJ3721 named as F5,F6,F14,F18,F27,F41 were isolated.The strain F6 and strain F18 showed the strongest antibacterial effect against R.solanacearum ZJ3721.By comparing the inhibition of its cell-free culture again R.solanacearum,strain F18 was selected as the experimental strain.In addition to the antagonistic effect on R.solanacearum ZJ3721,the strain F18 also has a strong inhibitory effect on the pathogenic fungi such as Verticillium dahliae,T.basicola,Fusarium oxysporum.sp.cucumebrium Owen,Fusarium oxysporum f.sp.Vasinfectum,Fusarium oxysporum f.sp.cubense.2.Based on the morphological and culture characteristics,physiological and biochemical characteristics and 16S rRNA gene sequence,the strain F18 was identified as Streptomyces.3.By optimizing the nutrient composition of fermentation medium and fermentation conditions of strain F18,the optimum medium composition was:soluble starch 1%,soybean peptone 0.4%,K2HPO4 0.05%,MgSO4 0.05%,NaCl 0.05%,FeSO4 0.01‰?.The optimal fermentation conditions were pH8,culture temperature 28 ?,loading volume 65 mL/250 mL,inoculation concentration 6%,shaking speed 180 rpm,culture time 132h.The antibacterial ability of the cell-free culture of strain F18 to R.solanacearum ZJ3721 was improved after the fermentation conditions were optimized.The antibacterial substance produced by strain F18 was mainly extracellular metabolites,which was soluble in water,methanol and ethanol,but not in other organic solvents.4.The organic fertilizer added with 10%(M/V)of the amino acid hydrolyzate was beneficial to the growth and reproduction of the strain F18,and also was beneficial to the production of the antibacterial active substance.The pot experiment and the field experiment showed that the organic fertilizer added with amino acid was beneficial to the colonization of the strain F18 in the soil.Application of strain F18 and bio-organic fertilizer can inhibite on the numbers of R.solanacearum in rhizosphere soil of tomato and promote the plant growth.Control efficancy of tomato bacterial wilt by application of bio-organic fertilizer was higher than that by irrigating the suspension of strain F18 into soil.