Involvement of catalase in bacterial Blight disease development of rice caused by Xanthomonas oryzae pv. oryzae

We investigated the role of catalase in determining the virulence of Xanthomonas oryzae pv. oryzae isolates and the reaction of different rice cultivars to virulent isolates. Catalase, being an antioxidant enzyme, plays a major role in combating the toxic effect of reactive oxygen species (ROS) in plant cells. Among the 11 isolates studied, a variable level of catalase activity and differential expression of isoforms in different isolates was recorded. The maximum level of catalase activity was found in isolate XOO2 followed by XOO4, and the minimum level of activity was recorded in isolate XOO3. A virulence assay conducted on the susceptible rice cultivar Jaya revealed that the bacterial isolate with the highest level of catalase activity caused the maximum lesion length and vice versa. Among 31 cultivars screened, cv. CTH-1 showed the lowest incidence of disease, and lesion length was almost nil. The cultivars Thanu, Rasi and CTH-3 were found to be highly susceptible to X. oryzae pv. oryzae infection. We discuss the possible use of catalase enzyme as a biochemical marker in studying the virulence of X. oryzae pv. oryzae isolates.