Screening Of Antagonistic Strains Against Fusarium Wilt On Tomato And Cucumber And Their Biological Control Effects

Tomato and cucumber are very important protected cultivation vegetables,which are susceptible to fusarium wilt.It not only affects the yield of tomato and cucumber seriously,but also is difficult to control.In this regard,domestic and foreign scholars have carried out a lot of research to explore the use of biological control strains for disease control.The use of biocontrol strains can solve these problems to some extent,and accumulate biocontrol resources for the preparation and use of biocontrol agents in future production practice.In this study,110 strains were isolated and identified from rhizosphere soil of tomato,rhizosphere soil of associated tiller onion and rhizosphere soil of tomato induced by root-knot nematodes,by using the method of plate confrontation,the strains with more than 50% inhibitory effect on Fusarium oxysporum f.sp.lycopersici and Fusarium oxysporum f.sp.Cucumerinum were obtained.In addition,the antagonistic strains with good comprehensive characters were screened by pot experiment of tomato and cucumber.The growth-promoting characteristics of tomato and cucumber were further verified by the test,so as to determine the effective control of fusarium oxysporum f.sp.Vasinfectum.This study provided the reference and practical basis for the biological control of Fusarium oxysporum f.sp.cubense in tomato and cucumber.The main results of this study are as follows:(1)Twenty-two antagonistic bacteria against FOL,FOC and Phytophthora capsici were isolated from tomato rhizosphere soil,tomato rhizosphere soil accompany with potato-onion and tomato rhizosphere soil inoculated with root-knot nematodes,the inhibition rate of antagonistic bacteria was above 40%.Among them,8 strains were antagonistic to Phytophthora capsici,14 strains were antagonistic to FOC and 12 strains were antagonistic to FOL.(2)The antagonistic activities of 22 antagonistic bacteria against Phytophthora capsici,FOL and FOC were determined by the plate confrontation method,the inhibition rate of Z15 to FOL was more than 50%(51.28%),and the inhibition rate of Z15 to FOC was 51.07%,54.49% and55.13% respectively.The 16 S r RNA gene sequences of four antagonistic bacteria were analyzed and their morphological characteristics were identified.Finally,three strains of Bacillus(Z4,Z31,L5)and one strain of Stenotrophomonas maltophilia(Z15)were identified.(3)The biocontrol efficacy of the four antagonistic bacteria against FOC was tested in tomato and cucumber seedlings.The biocontrol efficacy of strains L5,Z31 and Z4 against FOC was 55.26%,50% and 36.85%,respectively,the control efficacy of strain Z15 against tomato FOL was 47.65%.The four antagonistic bacteria showed high control efficacy,which was of great research value.(4)The four antagonistic bacteria Z4,Z31,L5 and Z15 showed that the optimum p H of Z4 and L5 was 6.0,the optimum p H of Z31 and Z15 was 7.0,all the four antagonistic bacteria had ability to produce IAA and siderophore.In conclusion,strains Z15,L5 and Z31 with high inhibition activity and biocontrol effect on Fusarium wilt of tomato and cucumber were screened in this study,it provided the theoretical basis and technical support for the research and development of biocontrol bacteria to control Fusarium wilt of tomato and cucumber.