Heat‐Inactivated Culture of Burkholderia gladioli BNM349 Reduces the Severity of Bacterial Canker and Bacterial Spot in Tomato

ABSTRACT

Bacterial diseases are major constraints in tomato production, particularly bacterial canker caused by Clavibacter michiganensis and bacterial spot caused by different Xanthomonas species. The limited effectiveness of chemical bactericides, the emergence of resistant strains and environmental concerns highlight the need for ecofriendly, sustainable strategies to control these phytopathogens. This study aimed to evaluate the biocontrol potential of a heat‐inactivated culture of Burkholderia gladioli strain BNM349 against major bacterial pathogens of tomato. Antibacterial activity of B. gladioli BNM349 culture‐derived preparations, including heat‐inactivated culture, cell‐free supernatant and butanol extract, was first assessed in vitro against C. michiganensis , X. vesicatoria and X. euvesicatoria pv. perforans . All BNM349‐derived preparations inhibited pathogen growth, although the extent of inhibition varied depending on the preparation type and pathogenic bacterial species. Greenhouse experiments further demonstrated that soil application of the heat‐inactivated culture significantly reduced bacterial canker severity by 40.1%, decreasing both disease progression and stem necrosis. The same treatment also reduced bacterial spot severity caused by X. vesicatoria by 48%. In contrast, the cell‐free supernatant had no significant effect on disease severity. These results indicate that heat‐inactivated cultures of B. gladioli BNM349 retain bioactive compounds capable of suppressing bacterial diseases in tomato, highlighting the potential of non‐viable microbial preparations as an environmentally friendly strategy for crop disease management.