Determination of antibacterial activity of various broad spectrum antibiotics against Xanthomonas oryzae pv. oryzae, a cause of bacterial leaf blight of rice

Abstract

Bacterial leaf blight (BLB) of rice (Oryza sativa L.) caused by Xanthomonas oryzae pv. oryzae, is arguably the most holistic pathosystem of rice throughout the worldwide due to its growing concern as this disease is wide spread, devastating and its control measures are still not well understood. In vitro evaluation of various broad spectrum antibiotics viz., streptomycin sulphate, kanamycin sulphate, chloramphenicol, ampicilin trihydrate and benzylpenicillin, was carried out to determine the best chemistry against the destructive pathogen Xanthomonas oryzae pv. oryzae at different concentrations. Inhibition zones appeared on petri plates for the growth of bacteria were very clear around the paper disks. Chloramphenicol proved to be the most effective antibiotic to control the bacterium as it suppressed the bacterial growth to greater extent and only the 6.25 mean bacterial colonies were appeared in the petri plates, followed by the ampicillin trihydrate which showed to be the second most effective antibiotic against the pathogen growth and retarded to 12.00 mean bacterial colonies. The maximum diameter of inhibition zone (28.31 mm) was showed by the Chloramphenicol at 100 ppm followed by ampicillin trihydrate which gave proved to be second most effective antibiotic to control the pathogen and gave maximum inhibition zone (25.02 mm) at 100 ppm concentration. All the antibiotics showed significant results at higher concentrations. The study suggests that the experiments in the field must be conducted to prove the effectiveness of these broad spectrum antibiotics in the natural environmental conditions as there is a possibility of some variation in the field results because of various factors which influence the chemical management of plant diseases in the field.