| dc.description.abstract | Bacterial wilt of brinjal, caused by Ralstonia solanacearum is a most devastating disease in
humid tropic. The isolated bacterium from brinjal plant was found to produce pink or light
red color or characteristic red center and whitish margin on nutrient agar medium after 24
hours of incubation. Biochemical characterization including gram’s staining, catalase
oxidase test, levan production from sucrose, lipase activity on tween 80 agar, arginine
dihydrolase reaction, Nacl tolerance test, starch hydrolysis test, nitrate reduction test, gas
production from nitrate (demystification) and potassium hydroxide solubility test revealed
that the isolated bacterium was R. solanacearum. Pathogenicity test revealed that the
isolated bacterium can cause wilt disease in brinjal plant. All biochemical tests in
combination with the pathogenicity test confirmed the isolate as R. solanacearum. The
present study was conducted to develop effective antibacterial agent without any residual
effect, and to analyze the in-vitro antibacterial potential of Calotropis procera (Akanda),
Ricinus communis (Castor) against the isolate Ralstonia solanacearum. The antibacterial
activity of the methanol, water and petroleum ether extracts was assayed by using disc
diffusion method. The results of antibacterial activity revealed that the average zone of
inhibition of the Akanda leaf extracts was more in the methanol extract (4.83 cm) than in the
water extract which showed zero zone of inhibition. In case of Castor the maximum zone of
inhibition was found using methanol extract (2.1 cm) where, both petroleum ether and water
showed same zone of inhibition (1.5 cm).Minimum Inhibitory Concentration (MIC) and
Minimum Bactericidal Concentration (MBC) was determined by two fold micro broth serial
dilution method with methanol solvent as the solvent reported the best result against the
bacteria in zone of inhibition. The result of Minimum Inhibitory Concentration and Minimum
Bactericidal Concentration was found best at 67.5μg/ml using Akanda leaf extract than
Castor leaf extract (125 μg/ml) with methanol solvent. In viable cell counting test both of the
plant, Akanda leaf extract and Castor leaf extract with methanol inhibited 100% of the
bacterial growth at 200 min time exposure that means both of the plants are effective against
the growth of R. solanacearum. | en_US |
