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

摘要

In the present work, we studied the role of antioxidant scavenging enzymes of plant pathogenic bacteria: catalase, ascorbate peroxidase and a virulence factor; extracelluar polysaccharide production in determining the virulence of?Xanthomonas oryzae?pv.?oryzae?(Xoo)?isolates and its differential reaction to rice cultivars. A varied level of antioxidant scavenging activity and exopolysaccharide production was observed among 34 isolates studied, and most of the?Xoo?isolates with higher catalase activity also exhibited higher ascorbate peroxidase activity. The maximum level of catalase (45 μM H2O2?min-1?mg-1?protein), ascorbate peroxidase (29 μM ascorbate min-1?mg-1?proteins) activity and exopolysaccharide production (70 mg) was found in isolate?Xoo32 which induced maximum 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-chemical markers in determining the virulence of?Xoo?under laboratory conditions.