Role of antioxidant scavenging enzymes and extracellular polysaccharide in pathogenicity of rice bacterial blight pathogen Xanthomonas oryzae pv. oryzae

摘要

The role of antioxidant scavenging enzymes of plant pathogenic bacteria: catalase, ascorbate peroxidase and a virulence factor; extracelluar polysaccharide prodn. in detg. the virulence of Xanthomonas oryzae pv. oryzae (Xoo) isolates and its differential reaction to rice cultivars was studied. A varied level of antioxidant scavenging activity and exopolysaccharide prodn. was obsd. among 34 isolates studied, and most of the Xoo isolates with higher catalase activity also exhibited higher ascorbate peroxidase activity. The max. level of catalase (45 μM H2O2 min-​1 mg-​1 protein)​, ascorbate peroxidase (29 μM ascorbate min-​1 mg-​1 proteins) activity and exopolysaccharide prodn. (70 mg) was found in isolate Xoo32 which induced max. lesion length on cultivar 'Jaya' upon clip inoculation in virulence assay. Among the 44 cultivars screened, cultivar 'Jeerigesanna' recorded least bacterial blight disease incidence, with 0.7 cm lesion length. The activity of catalase, ascorbate peroxidase and exopolysaccharide can be employed as bio-​chem. markers in detg. the virulence of Xoo under lab. conditions.