Rhizobacterial community-level, sole carbon source utilization pattern affects the delay in the bacterial wilt of tomato grown in rhizobacterial community model system

Characterizing rhizomicrobial community structure is important to our understanding of the mechanisms of suppressive soils towards soilborne plant diseases. We investigated whether the bacterial community structure, i.e., the number of the constituent bacterial strains and the community-level, sole carbon source utilization pattern of rhizobacteria estimated by BIOLOG EcoPlates, affects bacterial wilt of tomato. To assess their impact on the bacterial wilt, we used 15 artificial soil systems into which 5–20 rhizobacterial isolates from a disease-suppressive soil were inoculated. Although most of the tomato plants wilted by 16 days after pathogen inoculation, significant negative relationships were observed between the number of wilted plants, the number of the bacterial strains and the number of carbon sources that the rhizobacterial community was able to utilize. BIOLOGs showed that several carbon sources were utilized by the pathogen but not by the rhizobacterial community from the fastest-wilting treatments, suggesting that competition between the pathogen and the other rhizobacteria for carbon sources played an important role in suppressing the growth of the pathogen.