Rai, BimlaNaveena, Sirivella2020-10-292020-10-292020M/PP/268/2018-19https://krishikosh.egranth.ac.in/handle/1/5810153938In the present research work, the pathogen, Xanthomonas oryzae pv.oryzae was isolated from the Bacterial leaf blight infected rice plants. Infected samples are collected from the Pusa field of Bihar. The pathogen was identified as Xanthomonas oryzae pv.oryzae through isolation study (colony characteristics on TZC media), ooze test, pathogenicity test and different biochemical test. The pathogen showed yellow, smooth, raised, buttery colonies on nutrient agar medium. The results of biochemical studies revealed that the isolated Xanthomonas oryzae pv.oryzae were gram-negative, rod shaped and the pathogen showed positive reactions for potassium hydroxide test, catalase test, production of hydrogen sulphide whereas it showed negative reaction for oxidase test, nitrate reduction test and indole test. A total of 14 rhizobacteria were isolated from rhizosphere of rice plant and were screened in vitro for their bio control against Xanthomonas oryzae pv.oryzae in which 4 isolates were effective.RRB-13(Pseudomonas) showed the highest inhibition zone (18.1mm) after 48hrs of incubation. Seven antibacterial compounds (3 antibiotics & 3 chemicals) were evaluated against Xanthomonas oryzae pv.oryzae. Among the antibiotics Streptomycin showed highest antibacterial activity at all the three concentrations (250ppm, 500ppm and 1000ppm) produced inhibition zone 18.43mm, 21.43mm and 25.43mm respectively. Among the three chemicals ,Tricyclazole showed highest inhibition zone of 10.7mm, 14.7mm and 17.7mm at 0.05%, 0.1% and 0.2% concentration. Nine aqueous and ethanol extracts of botanicals were studied in vitro against Xanthomonas oryzae pv.oryzae. Among aqueous extract, Neem (Azadirachta indica) at 100% concentration found to be very much effective and showed an inhibition zone of about 23.4 mm. Among all the nine botanicals tested, Neem showed the high inhibition zone at all the three concentrations (20%, 30% and 40%) of 16.7mm, 17.4mm and 18.4mm respectively. Among the 9 ethanol extract of botanicals tested at 100% concentration, Garlic (Allium sativum) showed the high inhibition zone of 25.1mm. The ethanol extract of botanicals tested, garlic showed the high inhibition zone at the three different concentrations (20%, 30% and 40%) of 17.4mm, 18.4mm and 19.4mm respectively. Six essential oils were tested in vitro for their antagonistic nature in contrary to Xanthomonas oryzae pv.oryzae. Among them, Lemon grass oil showed highest inhibitory activity at 2000ppm (16.76mm). Citronella oil gave the good result at 500ppm (12.1mm) and 1000ppm (13.4mm).EnglishThesis