烟草根黑腐病根际拮抗菌的筛选、鉴定及其促生防病效果

为挖掘对烟草根黑腐病菌有较高拮抗效果的根际促生菌资源，从四川广元和陕西汉中等地采集30份烟草根际土壤，以烟草根黑腐病菌为靶标，采用温度筛选法和平板对峙法分离筛选出有高效拮抗活性的菌株，并对该菌株进行系统发育分析，采用抗生素标记法和温室盆栽法测定菌株LY79的定殖规律、对烟草的促生效果以及对烟草根黑腐病的防治效果。结果表明：（1）从烟草根际土壤分离到一株烟草根黑腐病高效拮抗菌株LY79，经形态学、生理生化鉴定结合16S rRNA和持家基因ropB分析将菌株LY79鉴定为解淀粉芽孢杆菌（Bacillus amyloliquefaciens）。（2）抗生素标记菌株LY79^A在烟草根际土定殖规律为先下降后上升再下降最终趋于稳定，且施药40 d后仍能在烟草根际土、根系、茎、叶分离到1.34×10⁶、2.91×10⁴、1.81×10⁴、1.01×10⁴ CFU/g的菌株LY79^A，说明其定殖能力较强。（3）菌株LY79对烟草促生效果较好，处理60 d后，烟草的株高、茎粗、整株干质量、根干质量分别增加了34.68%、37.85%、103.79%、72.55%。（4）1×10⁹ CFU/mL浓度的菌株LY79发酵液对烟草根黑腐病的盆栽防效达71.54%，仅略低于对照药剂70%甲基托布津500倍液。解淀粉芽孢杆菌LY79在烟草根黑腐病防治中具有较大的应用潜力。

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.