Screening And Antagonistic Bacteria Against Soil-Borne Diseases Of Tomato And Isolation, Identification And Pathogenicity Determination Of Its Pathogens

Tomato Fusarium wilt and bacterial wilt are the two main soil borne disease of tomato. Fusarium Wilt of tomato is an important soil borne fungal diseases caused by Fusarium oxysporum. Pathogens infestation plants from root, cause vascular disease and plants wilting, it can occur from the plant seedling stage to mature stage. In recent years, with the expansion of facilities vegetable planting area, Fusarium wilt has become an important soil disease that is common, easy happening and rapid spread. Seriously affected the yield and quality of vegetables. In the laboratory, the antibacterial effect of 29 kinds of Fungicides on Fusarium oxysporum was determined by using mycelium growth rate method. Through the analysis of EC50 values, the results show that there are 10 kinds of fungicides on Fusarium oxysporum were high virulent (EC50<10mg/L). The virulence of 50% carbendazim is strongest against Fusarium oxysporum, EC50 is 0.1218 mg/L. Followed by 25% JS399-19, 10% flusilazole,25%SYP-Z048,5% has diniconazole,10% myclobutanil,75% chlorothalonil,3% Zhongshengmycin,50%iprodione,70% thiophanate methyl. Inhibitory effects of 29 fungicides on Ralstonia solanacearum were determined by the paper disc method. Through the analysis of EC50 values, the results show that there are 3 kinds of fungicides on Ralstonia solanacearum were high virulent. The virulence of 3% Zhongshengmycin is strongest against Ralstonia solanacearum,EC50 is 3.3742 mg/L. then 80% mancozeb,2% kasugamycin.To obtain antagonistic bacteria for biocontrol effect on Fusarium wilt and bacterial wilt of tomato,we screened and evaluated the control efficiencies of antagonistic bacteria against F. oxysporum and R. solanacearum in vitro.2062 strains were isolated and purified from rhizosphere soil of tomato in Shuyang, Suqian,Lishui in Jiangsu Province and Hailaer in Inner Mongolian Province. Test on antagonistic ability revealed that 21 strains showed strong and steady antagonism against F. oxysporum and R. solanacearum.The results of antibacterial substances research of antagonistic bacteria showed that:All the above 21 strains could produce protease and Phosphate solubilizing effect, whereas they could not produce chitinase and cellulase. Four strains could produce siderophore. In pot experiment, strains SY290 could control Fusarium wilt and bacterial wilt effectively, with control efficiency of 74.2% and 75.0%,respectively, and control efficiencies of strains SQ728, LS536 were all above 60%. Base on morphological characteristics,16s rDNA and gyr-B sequence analysis appraisal, SY177,SY290, SQ728 was identified to be Bacillus amyloliquefaciens, LS536 was identified to be Bacillus subtilis.Isolation, identification and pathogenicity analysis of Fusarium spp. from tomato rhizosphere in jiangsu tongshan, qintong and shuyang tomato demonstration base.150 strains of Fusarium were isolated from 12 samples of soil by Fusarium selective medium. Through strain morphological identification, found type ? and type ? have 111 strains, were F. oxysporum; Type ? had 32 strains, were F.solani; Type ? had 7 strains, were F. verticillioides. Molecular identification of the ITS gene sequences of 51 strains, the result of molecular identification and morphological identification are completely consistent. Determination 51 strains 3 types of Fusarium pathogenicity,6 strains were weak pathogenicity; 33 strains were moderately pathogenicity; 12 strains were highly pathogenicity. Through analysis the correlation of strain growth rate determination and pathogenicity, found that the strain growth rate and pathogenicity have a weak positive correlation. Analysis different types of Fusarium pathogenicity, found that F. oxysporum have the highest percentage in highly Virulent strains. Analysis the different regions of tomato pathogenic Fusarium pathogenicity, found that Shuyang have the highest percentage of highly Virulent strains. Analysis the Fusarium species distribution in different regions, found that Fusarium oxysporum was dominant species in tongshan, qintong and shuyang with frequencies of 66%,72% and 84%.