Background: In our previous study, a strain EBS03 with good biocontrol potential was screened out of 48 strains of cotton endophyte Bacillus subtilis by evaluating the controlling effect against cotton Verticillium wilt. However, its mechanism for controlling Verticillium wilt remains unclear. The objective of this study was to further clarify its con-trolling effect and mechanism against cotton Verticillium wilt. Results: The results of confrontation culture test and double buckle culture test showed that the inhibitory effects of EBS03 volatile and nonvolatile metabolite on mycelium growth of Verticillium dahliae were 70.03％ and 59.00％, respectively; the inhibitory effects of sporulation and microsclerotia germination were 47.16％ and 70.06％, respec-tively. In the greenhouse test, the EBS03 fermentation broth root irrigation had the highest controlling effect at 87.11％ on cotton Verticillium wilt, and significantly promoted the growth of cotton seedlings. In the field experi-ment, the controlling effect of EBS03 fermentation broth to cotton Verticillium wilt was 42.54％ at 60 days after cotton sowing, and the boll number per plant and boll weight in EBS03 fermentation broth seed soaking, root irrigation, and spraying treatments significantly increased by 19.48％ and 7.42％, 30.90％ and 2.62％, 15.99％ and 9.20％, respec-tively. Furthermore, EBS03 improved the resistance of cotton leaves against the infection of V. dahliae, and induced the outbreak of reactive oxygen species and accumulation of callose. In addition, the results of real time fluorescent quantitative polymerase chain reaction (RT-qPCR) detection showed that EBS03 significantly induced upregulation expression level of defense-related genes PAL, POD, PPO, and PR10 in cotton leaves, enhanced cotton plant resistance to V. dahliae, and inhibited colonization level of this fungal pathogen in cotton. Conclusion: Bacillus subtilis EBS03 has a good biological defense capability, which can inhibit the growth and coloni-zation level of V. dahliae, and activate the resistance of cotton to Verticillium wilt, thus increase cotton yield.

State Key Laboratory of Cotton Biology/Institute of Cotton Research of Chinese Academy of Agricultural Sciences, Anyang 455000, Henan, China;Engineering Research Centre of Cotton, Ministry of Education/College of Agriculture,Xinjiang Agricultural University, Urumqi 830052, Xinjiang, China

[1]BAI Hongyan;FENG Zili;ZHAO Lihong;FENG Hongjie;WEI Feng;ZHOU Jinglong;GU Aixing;ZHU Heqin;PENG Jun;ZHANG Yalin-.Effcacy evaluation and mechanism of Bacillus subtilis EBS03 against cotton Verticillium wilt)[J].棉花研究（英文）,2022(04):1-11

Effcacy,EBS03,buckle,sporulation,microsclerotia,coloni

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