Dual protective roles of plant beneficial bacteria in drought resilience and suppression of tomato bacterial canker caused by Clavibacter michiganensis subsp. michiganensis

Objective: This study aimed to evaluate the ability of two beneficial bacterial isolates to mitigate the effects of Clavibacter michiganensis subsp. michiganensis (Cmm) and drought stress on tomato plants.Materials and Methods: 30 isolates were screened for in vitro antagonism against Cmm; isolates TR21/1 and CA18 were selected for in vivo testing under Cmm infection, drought, and combined stress conditions. Results: Isolate TR21/1 showed the highest in vitro inhibition zone (27.26 mm) and reduced Cmm-related disease by 38-83% in vivo. Under drought stress, isolate CA18 increased plant biomass by 30-38%. Combined inoculation with TR21/1 and CA18 elicited the strongest response, increasing biomass by 124-174% and reducing disease severity by 56-69%. Conclusion: Both isolates were effective, but their combined application produced the greatest overall improvement.