A biocontrol Bacillus velezensis strain decreases pathogen Burkholderia glumae population and occupies a similar niche in rice plants

Bacillus velezensis strain IBUN 2755 has biocontrol capacity against Burkholderia glumae, a very important pathogen in rice. However, the mechanisms by which IBUN 2755 strain achieves control of B. glumae are still unclear. We determined that both IBUN 2755 and B. glumae are attracted by compounds present in the rice Fedearroz 2000 cv root exudates. Both strains could use the same root exudates compounds as the sole carbon source (alanine, proline, glucuronic acid, arabinose and manose), which suggests a possible niche overlap for both species. Importantly both strains were able to colonize rice plants as endophytes, showing that they are present in the same environment. The presence of IBUN 2755 reduced B. glumae endophytic population both in root and shoot through the crop cycle, reducing disease symptoms such the presence of empty grains, which is a major concern for rice growers. Our results suggest that IBUN 2755 acts as a biocontrol strain by reducing the populations of B. glumae in rice plants with its capacity to compete for this particular ecological niche being one of the putative mechanisms of action of this strain.