<![CDATA[Background: Bacterial leaf blight is one of the major diseases in rice caused by Xanthomonas oryzae pv. oryzae, which can significantly reduce rice productivity. The use of chemical bactericides may cause environmental problems; therefore, biological control using antagonistic bacteria such as Bacillus spp. is considered a sustainable alternative. This study aimed to evaluate the inhibitory potential of Bacillus mycoides Ba-11 and Bacillus sp. Bcz-20 against Xanthomonas sp. under in vitro conditions. Method: The experiment was conducted using a completely randomized design with three treatments: Bacillus mycoides Ba-11, Bacillus sp. Bcz-20, and a control (sterile distilled water), each with nine replications. Antagonistic activity was tested using the well diffusion method on nutrient agar. The diameter of inhibition zones was measured after 24–48 hours of incubation and analyzed using the Dunn test at a 5% significance level. Result: Both Bacillus mycoides Ba-11 and Bacillus sp. Bcz-20 formed inhibition zones categorized as moderate to strong, indicating their ability to suppress the growth of Xanthomonas sp. Although Bacillus sp. Bcz-20 produced a larger inhibition zone, statistical analysis showed no significant difference between the two isolates. Conclusion: Both Bacillus mycoides Ba-11 and Bacillus sp. Bcz-20 have comparable and significant potential as biological control agents against Xanthomonas sp. through antibiosis mechanisms.]]>
