<![CDATA[Abstract. Putri RY, Santosa AI, Prakoso AB, Arwiyanto T. 2026. Phyllosphere bacterial communities associated with bacterial leaf blight symptoms and indigenous antagonistic bacteria against Xanthomonas oryzae pv. oryzae. Biodiversitas 27 (9): d270907. https://doi.org/10.13057/biodiv/d270907. Xanthomonas oryzae pv. oryzae, the causal agent of Bacterial Leaf Blight (BLB), may alter phyllosphere bacterial communities associated with rice health. This study characterized phyllosphere bacterial communities of healthy and BLB-symptomatic Mekongga rice plants and evaluated candidate phyllosphere bacteria for BLB suppression. Xoo was confirmed by phenotypic, pathogenicity, hypersensitive reaction, and Xoo3350-specific PCR assays. Phyllosphere bacterial communities were characterized using full-length 16S rRNA gene metabarcoding with Oxford Nanopore sequencing. The microbiome was dominated by Pseudomonadota, Bacteroidota, and Bacillota. Chryseobacterium was relatively more abundant in BLB-symptomatic plants, whereas Pseudomonas was relatively more abundant in healthy plants. Shannon diversity did not differ significantly between groups (p = 0.1266), whereas Pielou’s evenness was lower in BLB-symptomatic plants (p = 0.0495). Given the small sample size (n = 3 per group), this finding should be considered preliminary and hypothesis-generating rather than definitive evidence of disease-associated changes in community evenness. Of 56 fluorescent bacterial isolates recovered under the selective culture conditions, 44 (78.57%) inhibited Xoo growth in vitro. Isolate P50 showed the strongest disease suppression under greenhouse conditions, with a final disease severity of 31.70%, an AUDPC of 506.06 %-days, and control efficacy of 63.96-64.64% across the two rice varieties. Molecular analysis affiliated P1 and P5 with Aquipseudomonas alcaligenes and P50 with the Pseudomonas putida group based on 16S rRNA sequences. P50 was associated with the healthy rice phyllosphere and showed consistent disease-suppressive activity across the two rice varieties, supporting its further evaluation as a candidate biological control agent against BLB.]]>
