Biocontrol of the phytopathogens Xanthomonas oryzae pv. oryzae and Dickeya zeae with epiphytic and endophytic bacteria
摘要
The use of antagonistic microorganisms to control phytopathogens is gaining increasing attention due to the urgent need to reduce agrochemical usage. This study reports two rice-associated bacterial strains, Bacillus velezensis VY03 and Pantoea ananatis VY148, that strongly antagonize Xanthomonas oryzae pv. oryzae (Xoo), the causal agent of bacterial leaf blight (BLB), and Dickeya zeae (Dz), which causes foot rot disease. Strain VY03 exhibited an effective endophytic lifestyle, with a cell density of 9.8 × 105 CFU⋅g−1 in roots and grew epiphytically at a lower density of 4.9 × 103 CFU⋅g−1 in roots. Conversely, strain VY148 only grew epiphytically, reaching a cell density of 1.3 × 107 CFU⋅g−1 in roots. Genome analysis revealed diverse gene clusters associated with antimicrobial metabolite biosynthesis in both strains, highlighting their potential as biological control agents. Additionally, the genomes of VY03 and VY148 contain distinct gene complexes involved in plant cell wall degradation, which may reflect their respective endophytic/epiphytic lifestyles. In planta experiments demonstrated that VY03 preferentially antagonized Dz infection, whereas VY148 was more effective against Xoo. This selective competition between epiphytic and endophytic bacteria influences their preventive effects on phytopathogens, with niche exclusion proposed as the underlying mechanism.