Phenotypic and Molecular Characterization of Xanthomonas oryzae pv. oryzae Strains Causing Bacterial Blight in Rice

Abstract

Bacterial blight caused by Xanthomonas oryzae pv. oryzae is one of the most destructive diseases of rice, leading to substantial yield losses and reduced grain quality in major rice-growing regions. Accurate characterization of pathogen strains is essential for understanding pathogenic variability and developing effective disease management strategies. The present study investigated the phenotypic and molecular characteristics of X. oryzae pv. oryzae strains collected from bacterial blight-infected rice fields. Diseased leaf samples exhibiting typical water-soaked and yellowing symptoms were collected from different agroecological regions, and bacterial isolates were obtained using standard isolation techniques. Phenotypic characterization included assessment of colony morphology, pigmentation, biochemical reactions, growth behavior, and pathogenicity on susceptible rice cultivars. Considerable variation in virulence and symptom expression was observed among the tested strains. Molecular characterization was performed using polymerase chain reaction (PCR)-based analysis and sequence comparison of conserved genomic regions to confirm pathogen identity and evaluate genetic diversity. Phylogenetic analysis revealed significant genetic variability among isolates, indicating the presence of diverse pathogen populations associated with rice bacterial blight. Certain strains exhibited close genetic relationships despite geographical separation, suggesting possible dissemination through infected seed materials and cultivation practices. The integration of phenotypic and molecular approaches improved the accuracy of pathogen identification and provided comprehensive insights into strain diversity and population structure. The findings contribute valuable information for resistance breeding programs, epidemiological studies, and the development of integrated disease management strategies aimed at minimizing bacterial blight incidence and sustaining rice productivity.