IN VITRO AND IN VIVO EVALUATION OF BACTERIAL ANTAGONISTS AGAINST TOMATO BACTERIAL SPOT DISEASE

Abstract

This study evaluates the biocontrol potential of bacterial antagonists against Xanthomonas vesicatoria (Xv)the causative agent of bacterial spot disease in tomatothrough both in vitro and in vivo assessments. Thirty bacterial isolates exhibiting epiphytic and endophytic traits were screened for antimicrobial activity against Xv. In vitro assays identified isolates 35E and 6E as the most effectiveproducing inhibition zones of 25.99±0.41 mm and 24.70±0.61 mmrespectively. In vivo trials demonstrated that isolate 35E consistently reduced disease severity from 40–41% in the positive control to approximately 19%achieving stable suppression under in vivo conditions. Molecular characterization revealed that isolate 35E showed 96.56% 16S rDNA sequence similarity to Bacillus cereussupporting its known biocontrol and plant growth-promoting properties. The results highlight the promise of Bacillus cereus CA18 as an effective biocontrol agentoffering a sustainable alternative to chemical pesticides for managing bacterial spot disease in tomato.