Biochemical characterization of pseudomonas syringae pv. syringae of okra (abelmoschus esculentus l.) moench in Rajasthan

Bacterial leaf blight disease of okra caused by Pseudomonas syringae pv. syringae is an emerging disease and great threat for production of okra in Rajasthan. A survey was conducted to know the status of bacterial leaf blight of okra in terms of its incidence and severity and to characterize the pathogen causing the disease. Eighty nine seed samples of okra (Abelmoschus esculentus L.) Moench were collected from 15 major okra growing districts of Rajasthan and subjected to dry seed examination. All the seed samples were categorised as asymptomatic, bold discoloured and heavily discoloured seeds collected during 2011; 2012 and 2013 growing seasons of okra. The samples were collected from farmer’s field, market and farm storage (houses). Eighty nine seed samples of okra belongings to 15 districts of Rajasthan, India revealed asymptomatic (15.25-83.75%), bold discoloured (07.5-54.25%) and heavily discoloured seeds (02.25-34.75%) in dry seed examination. The discoloured seeds included brown black or water soaked symptoms and such seeds on incubation yielded the bacterium. At seedling stage, seedling shows failure or delayed seeds germination, bacterial oozing and rotting that resulting collapse of hypocotyls and cotyledonary leaves that resulting seedling mortality. So the seed losses seed germination, seedling are symptomatic that increase seedling mortality. High incidence of pathogen was found in Jhalawar, Jaipur, Kota, Sawai Madhopur and Bharatpur. Twenty four bacterial isolates were obtained from the infected seeds and plant material collected from field during the survey. Pathogenicity test on host plant leaves confirmed the bacterium was Pseudomonas syringae pv. syringae (PSS) but HR test (hypersensitivity test) in tobacco leaves with pathogen isolates showed weak positive reaction of tissues where infiltrated. The causal bacterium was also characterized by biochemical tests and results of the all the tests revealed that the causal organism of leaf blight disease of okra was Pseudomonas syringae pv. syringae.