Biocontrol potential of the endophytic Bacillus amyloliquefaciens YN201732 against tobacco powdery mildew and its growth promotion

Abstract

The effectiveness of Bacillus amyloliquefaciens YN201732, a beneficial endophyte isolated from tobacco seeds was explored for control of tobacco powdery mildew and the systemic resistance mechanisms involved. The results of the study showed that endophyte YN201732 has antagonistic effects on 12pathogenic fungi. The fermentation broth can inhibit the spore germination and has good control effect on tobacco powdery mildew in the greenhouse. The control effect of the protective test and the therapeutic test at 14 days reached up to 71.09% and 86.11%, respectively. Moreover, endophyte YN201732 can also promote seed germination and seedling plant growth, and improve plant photosynthesis. Compare with water treatment, the root length, plant height, maximum leaf length, leaf width, fresh weight, dry weight, chlorophyll and net photosynthetic rate of tobacco seedlings increased by 32.27%, 86.67%, 154.92%, 107.25%, 664.71%, 207.69%, 150.33%, and 240%, respectively. Additionally, the expression of NPR1 in tobacco leaves was stable when inoculated with YN201732 at different time points, while the PDF1.2 gene was up-regulated rapidly, suggesting that jasmonic acid/ethylene signaling pathway of plant might be induced, which enhance plant resistance to powdery mildew. The chit and PPO genes were highly expressed while the PAL and POD defense enzyme genes were down-regulated, the expression of chit was up-regulated 30–70 times after induction treatment. In addition, we revealed that polyphenol oxidase and chitinases are closely related to tobacco induced resistance to powdery mildew. Thus, our study showed that B. amyloliquefaciens YN201732 has high potential to be used as biocontrol agent and plant-growth promoting bacterium in tobacco agriculture.