Verticilllium wilt of cotton is a devastating soil-borne disease, which is caused by Verticillium dahliae Kleb. Bacillus velezensis strain AL7 was isolated from cotton soil. This strain efficiently inhibited the growth of V. dahliae. But the mechanism of the biocontrol strain AL7 remains poorly understood. To understand the possible genetic determinants for biocontrol traits of this strain, we conducted phenotypic, phylogenetic and comparative genomics analysis. Phenotypic analysis showed that strain AL7 exhibited broad-spectrum antifungal activities. We determined that the whole genome sequence of B. velezensis AL7 is a single circular chromosome that is 3.89 Mb in size. The distribution of putative gene clusters that could benefit to biocontrol activities was found in the genome. Phylogenetic analysis of Bacillus strains by using single core-genome clearly placed strain AL7 into the B. velezensis. Meantime, we performed comparative analyses on four Bacillus strains and observed subtle differences in their genome sequences. In addition, comparative genomics analysis showed that the core genomes of B. velezensis are more abundant in genes relevant to secondary metabolism compared with B. subtilis strains. Single mutant in the biosynthetic genes of fengycin demonstrated the function of fengycin in the antagonistic activity of B. velezensis AL7. Here, we report a new biocontrol bacterium B. velezensis AL7 and fengycin contribute to the biocontrol efficacy of the strain. The results showed in the research further sustain the potential of B. velezensis AL7 for application in agriculture production and may be a worthy biocontrol strain for further studies.

棉花黄萎病是一种破坏性的土传病害，由大丽轮枝菌引起。Bacillus velezensis菌株 AL7 从棉花土壤中分离出来。该菌株有效地抑制了大丽花的生长。但生物防治菌株 AL7 的机制仍然知之甚少。为了了解该菌株生物防治性状的可能遗传决定因素，我们进行了表型、系统发育和比较基因组学分析。表型分析表明菌株AL7表现出广谱抗真菌活性。我们确定了B. velezensis的全基因组序列AL7 是一个单环状染色体，大小为 3.89 Mb。在基因组中发现了可能有益于生物防治活动的假定基因簇的分布。通过使用单个核心基因组对芽孢杆菌菌株进行的系统发育分析清楚地将菌株 AL7 置于B. velezensis 中。同时，我们对四种芽孢杆菌菌株进行了比较分析，并观察到它们基因组序列的细微差异。此外，比较基因组学分析表明，核心基因组B. velezensis是在基因更丰富相关相比次级代谢枯草芽孢杆菌菌株。fenycin 生物合成基因中的单突变体证明了 fengycin 在B. velezensis AL7拮抗活性中的作用。在这里，我们报告了一种新的生物防治细菌B. velezensis AL7 和 fengycin 有助于该菌株的生物防治功效。研究结果表明，B. velezensis AL7 在农业生产中的应用潜力得到进一步证实，可能是一种值得进一步研究的生防菌株。