Screening and Identification of Antagonistic Bacteria against Thielaviopsis basicola and Their Effects on Growth and Disease Prevention

In order to explore the plant growth promoting rhizobacteria (PGPR) resources with high antagonistic effect against tobacco root black rot, 30 tobacco rhizosphere soil samples were collected from Hanzhong and Guangyuan. The strains with high antagonistic activities against Thielaviopsis basicola were isolated and screened by temperature screening and the plate face-off method, and the strains were identified by phylogenetic analysis. The colonization ability of tobacco rhizosphere, the growth-promoting effect and the control effect of tobacco root black rot were determined by using the flat plate method, the antibiotic labeling method, and the greenhouse pot culture method, respectively. (1) Strain LY79, an antagonistic strain of tobacco root black rot, was isolated from tobacco rhizosphere soil and identified as Bacillus amyloliquefaciens by combining morphology, physiology and biochemistry with 16S rRNA and rpoB gene sequences. (2) The colonization of tobacco rhizosphere soil by LY79^A was decreased first, then increased, then decreased and finally tended to be stable, and 1.34×10⁶, 2.91×10⁴, 1.81×10⁴, 1.01×10⁴ CFU/g LY79^A strain could still be isolated from tobacco rhizomes, root, stem and leaf tissues after 40 days, This indicates that LY79^A has strong colonization ability. (3) LY79 had an obvious effect on the growth of tobacco. Plant height, stem diameter, dry weight and root dry weight were increased by 34.68%,37.85%, 103.79% and 72.55%, respectively. (4) LY79 with a concentration of 1×10⁹ CFU/mL had a control effect of 71.54% on the root black rot of tobacco in the pot experiment, slightly lower than the control effect of 500 X Metobuzin (70%). In summary, Bacillus amyloliquefaciens LY79 had great potential in the control of tobacco root black rot.