Study On The Colonization Dynamics Of Plant Endophytic Bacteria And Their Control Effects On Pepper Blight And Cotton Verticillium Wilt

Biological control was a method using antagonistic microorganisms to inhibit the growth of plant pathogens,which met the demands of the developing modem agriculture.In this paper,four different inoculation ways were used to study the colonization rule in potted pepper seedlings and the control effect on Phytophthora capsici of Pseudomonas fluorescens G9,J13 and R15;while in order to obtain endophytic bacteria which can efficiently inhibit Verticillium dahliae Kleb.growth,the purpose strains was isolated from the roots,stems and leaf of plants,the isolates was identified,the colonization dynamics and the control effect on cotton Verticillium wilt of the isolates was evaluated;in order to improve the stability of the isolates to control cotton verticillium wilt,the solid agent of endophytic bacteria and the solid agent of actinomycetes were mixed,then inoculation into the soil contained Verticillium dahliae spore suspension,which control effect on cotton Verticillium wilt was evaluated.The main results are as follows:Pseudomonas fluorescens G9,J13 and R15 could colonize in roots of potted pepper seedlings by single bacteria inoculation,mixture inoculation and crossover inoculation,but the number of colonization was different,the colonization was 105 cfu/g in single bacteria inoculation,the colonization was 104 cfu/g in mixture inoculation,the lowest colonization was 0 cfu.g-1 in crossover inoculation,the strain R15' could maintain colonization 6.30×105 cfu/g which control effect on Phytophthora capsici Leon.was 100%in single strain repeative inoculation experiment;in control effect test,there is a positive correlation between the control effect value and colonization in single strain inoculation once experiment;in single strain inoculation three times experiment,the control effect about Phytophthora capsici of the first inoculation endophytic bacteria>the second>the third,and which were significantly higher than the control group with metalaxyl pesticide group every time.The endophytic bacteria strains SZ5.DP 10 and CCM9 were selected for good antagonistic effect on the pathogens of Verticillium dahliae Kleb.on the agar disk diffusion,the isolates were identified using morphological and physiological tests combined with 16S rDNA and gyrB-based molecular analysis,the strain SZ5 was identified as Bacillus cereus,the strains DP 10 and CCM9 were Bacillus subtilis;the strain SZ5 could colonize in root,stem and leaf,the strains DP 10 and CCM9 could only colonize in root and stem,the quantity of colonization of three strains in cotton roots>stem>leaf;inoculation with Verticillium dahliae spore suspension 10 d after inoculation of endophytic bacteria strains in sterile soils,the control effect against cotton Verticillium wilt was up to 79.52%-89.79%.However,inoculation three endophytic bacteria strains into soil containing Verticillium dahliae spore,the control effect against cotton Verticillium wilt was about 23.77%-36.03%.The antagonistic relationship between the four actinomycetes 2010SF6-11,10TF3-7-17,102TF3-7-13,DK5406 and the three endophytic bacteria CCM9,SZ5,DP 10 were measured on the agar disk diffusion;in control effect test,the endophytic bacteria and actinomycetes were blend in a ratio of 1:1,1:2 and 2:1,inoculate into the soil contained Verticillium dahliae spore suspension,the result showed that DP10:DK56=2:1,the value of control effect on cotton Verticillium wilt was the highest,it was 85.42%,while the value of the other five groups was not significant,the average was 55.83%.