Biocontrol potential of Burkholderia spp. against Fusarium oxysporum f. sp. lycopersici infecting tomato.

BACKGROUND: Fusarium wilt of tomato caused by Fusarium oxysporum f. sp. lycopersici (FOL) is a serious disease. Host resistance and soil fumigation may reduce the impact of FOL, but the effectiveness may decrease over time due to the diversity and evolution of pathogens. Silicon is the second most abundant element in the Earth's crust, but has been overlooked in crop protection due to its poor availability to plants. Silicate-solubilizing bacteria (SSB) are reported to enhance soil nutrition, plant growth, and stress tolerance by transforming inorganic silicon into a plant-available form. Hence, SSB with antimicrobial properties can act as green alternatives to fungicides. Therefore, this study aims to isolate rhizospheric SSB and uncover their benefits in crop protection. RESULTS: Among thirteen potentially beneficial strains identified through 16S rDNA sequencing, Burkholderia contaminans NRBC (NRBC) and Burkholderia sp. NRBA (NRBA) were chosen for greenhouse experiments to evaluate their effectiveness in promoting plant growth and suppressing FOL (race 2). Under normal greenhouse conditions, the co-application of NRBC and silicon significantly increased shoot dry weight. Under FOL stress, all bacteria-treated groups were taller than the control groups. Bacterial treatments significantly reduced disease incidence and suppressed disease progression with no significant effect of the silicon supplement. The expression profiling of some defense-related genes revealed that soil-inoculation with NRBA and NRBC induced transcriptional patterns consistent with the involvement of salicylic acid (SA) and jasmonic acid/ethylene (JA/ET)-related defense responses. CONCLUSIONS: SSB isolates, NRBA and NRBC, are effective standalone biocontrol agents for managing Fusarium wilt in tomato. Silicon supplementation did not show the anticipated plant growth promotion of tomato plants and FOL suppression.