ASSESSMENT OF BACILLUS SPP. AS IN VITRO ANTAGONISTS OF XANTHOMONAS SP.

The genus Xanthomonas comprises one of the most relevant groups of phytopathogenic bacteria worldwide. Currently, more than 48 valid species are recognized, capable of infecting over 400 plant species. In this context, the present study aimed to evaluate the antagonistic potential of Bacillus strains against Xanthomonas sp. isolates under in vitro conditions. The experiment was conducted in a completely randomized design using a 2 × 3 factorial arrangement, consisting of two Xanthomonas isolates (X1 and X2) and three Bacillus strains (B1, B2, and B3), in addition to antibiotic control treatment, using the double-layer diffusion assay. Antagonistic activity was evaluated by measuring inhibition zones (cm). Data were subjected to analysis of variance, and means were compared using Tukey’s test at 5% probability. Significant effects of treatments and Xanthomonas isolates were observed on inhibition zone diameter (p < 0.001), with no significant interaction between the evaluated factors. Overall, Bacillus strains were able to inhibit the growth of the phytopathogen, although differences in inhibition zone size were observed among treatments and tested isolates. These results highlight the potential of Bacillus spp. strains as antagonistic agents against Xanthomonas sp. under in vitro conditions, supporting further studies to evaluate their effectiveness under in vivo conditions.