The screening, identification, and biocontrol potential of antagonistic endophytes against ginseng rust rot disease

Rust rot is a significant disease affecting Panax ginseng cultivation, leading to reduced yields and quality. Biological control has emerged as a promising method for managing this disease. Two endophytic bacteria X14 and X19 isolated from Panax ginseng were characterized as Bacillus amyloliquefaciens and Bacillus velezensis, respectively. The inhibition rates of the X14 and X19 cultures against Ilyonectria robusta XF3 were more than 99%. The pot experiment results indicated that the disease index of the treatment inoculated with XF3 was 60, while the disease index of the treatment inoculated with XF3 followed by X14, X19, and both strains was 8, 8, and 12, respectively. The disease control effects of all treatments exceeded 50%. Compared to the pathogen treatments, the inoculation with X14 and X19 significantly boosted the activities of PAL, CAT, and PPO in Panax ginseng roots. Following the inoculation with X14 and X19, the activities of polygalacturonase and β-glucosidase in ginseng roots were significantly reduced compared to the CK. The combined inoculation of X14 and X19 resulted in elevated activities of soil urease, soil cellulase, invertase, catalase, and acid phosphatase, with catalase, urease, and cellulase activities showing significant superiority over the CK. In summary, X14 and X19 strains exhibit potential as biocontrol agents against rust root rot of ginseng, warranting further exploration and applications.