Xanthomonas oryzae pv. oryzae (Xoo) is the disease-causing agent behind bacterial leaf blight (BLB) affecting the leaves at the plant growth phases of rice. It produces noticeable symptoms in infected rice, such as leaf blight, which appears on the leaves of rice plants adjacent to the leaf tips and margins. This study intends to explore bacterial Xoo isolates from 25 regions in Bangladesh through biochemical and molecular characterization. The bacterial isolates were grown in petri dishes on Peptone Sucrose Agar (PSA) medium, and the isolates had colonies ranging in size from 0.08 mm to 1.1 mm, and their color ranged from light yellow to yellow with a circular margin. Majority of the isolates produced raised and slimy colonies. The bacteria were then subjected to different biochemical tests resulting in positive for KOH (3%) test, gelatin liquefaction, catalase test, and while, negative for starch hydrolysis, gram reaction, and oxidase tests. Moreover, the DNA of Xoo-indicating bacteria was isolated, and among the 29 isolates, 15 Xoo-bacteria were confirmed through PCR amplification using a specific primer, Xoo2976. All 15 virulent Xoo-bacteria were subjected to a pathogenicity test on 3 rice varieties, BRRI DHAN49, IRBB66, and IRRI 154 yielded significant results in terms of disease severity. Xoo17 exhibits the highest virulence from the pathogenicity test. The study's outcomes may be utilized for screening BLB-resistant rice in varietal development research.

Keywords : Bacterial Leaf Blight; Characterization; Resistance; Xoo2976; Xanthomonas oryzae pv. Oryzae.