Abstract: This study aimed to screen compound microbial agents for disease control and growth promotion. Soil samples were collected from 26 cucumber fields in Gansu Province that had been continuously infected with Fusarium wilt for years. Antagonistic strains were screened using the plate confrontation method, and identified based on morphological, physiological, biochemical characteristics and gene sequencing analysis. The broad-spectrum antifungal and growth-promoting performances of antagonistic strains were subsequently determined. The results showed that strains L3-3, L3-1, 42-3 and L5-4 exhibited significant inhibitory effects against Fusarium oxysporum f. sp. cucumerinum Owen, and were identified as Burkholderia gladioli, Bacillus cereus, Lysobacter antibioticus and Bacillus velezensis, respectively. These four strains showed broad-spectrum resistance to eight different pathogenic fungi, among which L3-3 had the best antagonistic effect, L3-1 had the highest organic phosphorus-solubilizing capacity, 42-3 had the highest nitrogenase activity, and L5-4 produced the highest concentration of IAA. Field trials demonstrated that the equal-volume mixed formulation of the four strains achieved the optimal performance, with a control efficacy of 81.45%. Compared with the control group, the cucumber plant height, stem diameter, whole-plant fresh weight, yield, vitamin C, soluble sugar and soluble solids content increased by 5.86%, 11.25%, 8.60%, 12.37%, 37.86%, 20.19% and 22.03%, respectively.

Key words: isolation and identification, compound microbial agent, disease control and plant growth promotion effect