ANTIBACTERIAL EFFICACY OF NEEM (Azadirachta indica) AND LEMON (Citrus limon) IN IN VITRO AGAINST Xanthomonas oryzae pv. oryzae CAUSING BACTERIAL LEAF BLIGHT OF RICE

Abstract

Xanthomonas oryzae pv. oryzae is an important pathogen of rice causing bacterial leaf blight disease, resulting heavy yield losses. X. oryzae pv. oryzae was isolated and identified on the basis of morphological, biochemical characterization and pathogenicity test. Leaf extracts of Azadirachta indica (Neem) and Citus limon L. (Lemon) were evaluated for the antibacterial effect against the isolated and identified Xanthomonas oryzae pv. oryzae. Methanol and aqueous extract of leaves of both plants were tested by using disc diffusion method. The antibacterial efficacy was quantitatively assessed on the basis of zone of inhibition and minimum inhibitory concentration (MIC) along with minimum bactericidal concentration (MBC) on nutrient agar (NA) media. The results of disc diffusion method of antibacterial activity showed that the average zone of inhibition of A. indica leaf extract was higher in water extract (2.60 cm) than in methanol extract (1.90 cm). In case of C. limon, the maximum zone of inhibition was also found using water extract (2.30 cm) where methanol showed less zone of inhibition (1.60 cm). The MIC and MBC of water extract was found the best at 62.5 μg/ml using A. indica leaf extract where C. limon leaf extract gave 125 μg/ml. In cell viability test, both of the plant, A. indica and C. limon with water extract showed 100% cell death at 200 min time of exposure. The findings of the study suggest the use of water extracts of both A. indica and C. limon as the potential candidate to be used as an antibacterial agent against X. oryzae pv. oryzae.