Abstract：Cowpea (Vigna unguiculata) root rot is primarily a soil-borne fungal disease caused by Fusarium solani. This disease is particularly prevalent during the seedling stage of cowpea and poses significant challenges for prevention and control, especially in Hainan. Currently, there are no effective microbial agents available for its management. In this study, a strain designated ZF520, exhibiting a notable inhibitory effect on F. solani, was isolated from cowpea rhizosphere soil. Through morphological observation, determination of physiological and biochemical characteristics, and multi-gene phylogenetic tree analysis, this strain was identified as Bacillus velezensis. Antibacterial spectrum analysis revealed that strain ZF520 demonstrated significant antagonistic effects against 6 pathogenic fungi (F. oxysporum, Ascochyta citrullina, Rhizoctonia solani, F. solani, Corynespora cassiicola, Botrytis cinerea). Pot test results indicated a considerable reduction in the disease index of root rot when plants were inoculated with ZF520, achieving a control efficacy of 71.82%. A ZF520 seed coating agent was developed for cowpea seeds. This agent achieves a control effect on cowpea root rot of 76.67% without compromising the emergence rate, outperforming 23% imidacloprid fludioxonil difenoconazole 23% imidacloprid fludioxonil difenoconazole suspension seed coating agent treatment. The effective viable bacterial count of the microbial seed coating agent, formulated using ZF520 fermentation broth, was 1.5×109 CFU/mL. The coated strain maintained a stable rhizospheric colonization level of approximately 2.3×105 CFU/g in cowpea seedlings, demonstrating potential for mitigating pathogenic infection risks during the early growth stage through probable antagonistic mechanisms. In conclusion, strain ZF520 exhibits promising biocontrol potential and application prospects for managing cowpea root rot.
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