V. VEDA SREE*, M. PRADEEP, P. MADHUSUDHAN, P. ANIL KUMAR AND M. RAVEENDRA REDDY

Department of Plant Pathology, ANGRAU-S.V. Agricultural College, Tirupati-517 502.

ABSTRACT

Xanthomonas oryzae pv. oryzae (Xoo), the causal agent of bacterial leaf blight (BLB) in rice, poses a significant threat to rice cultivation in many parts of the world. The present study aimed to isolate and identify Xoo from infected rice leaves and confirm its pathogenicity, followed by preliminary biochemical and molecular characterization. Pathogenicity of the isolates was confirmed by clip inoculation on BPT 5204 cultivar, which reproduced BLB symptoms within 14 days. Biochemical characterization of the three isolates revealed catalase positivity, indicating the production of the catalase enzyme capable of breaking down hydrogen peroxide. The KOH solubility test yielded a positive result, supporting the Gram-negative nature of the isolates. However, the oxidase test was negative, which aligns with typical features of Xoo. Molecular characterization of three isolates was done with Xoo specific primers which yielded 290 bp size amplicon. These findings confirm the easy and reliable way to confirm the pathogen as Xoo without further sequencing.

KEYWORDS: Catalase, molecular characterization, oxidase, pathogenicity, Xanthomonas.