Antagonistic Tobacco Growth-Promoting Rhizobacteria Against Black Shank

Antagonistic Tobacco Growth-Promoting Rhizobacteriaagainst Black ShankTobacco Black shank is a serious disease. Rhizobacterium as biocontrol agents has been widely studied and some promising results have been obtained. The purpose of this study is to screen rhizobacteria as agents against Tobacco Black Shank or other tobacco soil brone disease.753 strains were isolated from 13 soil samples of Kunming Yuxi Dali Qujing. After screened on plate for restrain three pathogens, 97 isolates were first screened, then studying the germination of tobacco seeds soaked by bacteria suspension, 19 isolates were gained. Last tested the property of bacteria of promoting tobacco leaf height and the restrain efficient for blank shank, 7 isolates were screened. According to morphology, chemotrophy characters and the the result of ATB identification, RB-42, RB-89, RB78, RB-i, RB-59 R2 were identified as Pseudomonas fluorescens- I Pseudomonas fluorescens-2 Pseudoraonas aeruginosa Enterobacter gergoviae, Enterobacter clocae a~id Agrobacterium rc~dibacter. Based on the nitrate reductase activity, starch utilization and VP test, R4 characters were similar to Bacillus subtilis.Pseudomonas fiuorescens RB-42 and RB-89 marked with Rif and strepomtoycin successfully colonized on the root surface. At the condition of sterile soil and soil with chemotaxis, the number of root cap colonization more than the number of the root cap colonization in nonsterile soil and soil with no chemotaxis. The colonization mobility of marked strains on the root surface showed that the colonization number increased in prophase then decreased gradually, there are numbers of colonization in three weeks.The chemotaxis to tobacco root secretion of PGPR RB-89, RB-42, RB-2, RB-I were over 1, the highest chemotaxis is amino acid, then isorganic acid, last is sugny tyrosine. proline, glylcine, Phenylalanine, werethe high chemotaxis, histidine and theonine were no chemotaxis toRB-42 and RB-89. No difference between organic acid, only lactic acidhad more chomotaxis than others for RB-42 and RB-89.The mechanism were also tested. Those stralns with high productivityof HCN were same as those strains promoted Plant grOwth. Therhizobacteria restrained mycelium groWth, spOre germinaion and theproductivity of sporangium. The absorb activity fOr P all K, the Mn Zn PK Ca and Mg in tobacco root secretion were promoted, the pH inrhizophere were also declined after inoculated with rhizobacteria.