Effect of rain simulation on Xanthomonas oryzae pv. oryzae population density in guttation fluid and on the spread of bacterial blight in rice

Bacterial blight of rice caused by Xanthomonas oryzae pv. oryzae is most serious biotic constraint of rice production in Punjab, influenced mainly by environmental factors and nutritional factors applied to the rice crop. Present study aimed at observing the relationship between rain simulation and disease spread. More number of bacterial colonies was recovered from the susceptible rice cultivar (Pusa 1121) plants where no-rain was simulated as compared to those where rain was simulated. Mean bacterial log cfu in rain simulated plant was 4.88 as compared to 5.67 in non rain simulated plots after 1day of inoculation. The population densities of bacteria increased gradually in both the treatments. The log cfu of bacteria was 5.84 in rain simulated plots as compared to 6.28 in non rain simulated plots after 7 days of inoculation. However after 14 days of inoculation, the bacterial population in guttation fluid was foundto be non-significant at 5% level of significance in rain and non rain simulated plots but the bacterial population was found to be less as compared to that after 7 days of inoculation. Rain washed off the guttation fluid which resulted in decrease of bacterial load in the infected leaf. The significant difference at 5 % level of significance was observed between the per cent disease severity and disease spread was also observed in rain simulated plots and no rain simulated plots in cultivar Pusa 1121 which is a bacterial blight resistant cultivar