PLANT CELL BIOTECHNOLOGY AND MOLECULAR BIOLOGY

Nutrient paucity in the soil poses confront to global production of food. To boost the crop yield and food production, farmers use chemical nitrogen fertilizers. However, Such chemical fertilizers are not only expensive for the farmers but can also cause environmental damages such as pollution of water resources, also inhibit the natural flora of soil which support the growth of plant as well as also decrease the fertility of soil, and even contribute to the release of greenhouse gases.     Expanding eco-friendly approaches to improve plant growth and crop productivity is of great important for sustainable agriculture. Rhizobium is a gram negative bacteria which associates symbiotically and leads to the formation of root and stem nodules in legume plants. Rhizobium plays an important role in improving soil fertility by fixing nitrogen. Hence screening and selecting the proper rhizobial strain is important for biological nitrogen fixation. The present study was aimed to isolate and identify rhizobium from root and stem nodule of various leguminous plants on selective yeast extract mannitol agar (YEMA) medium. A total of 19 bacterial isolates were identified as rhizobia on the basis of authentication test (Congo red test, Glucose- peptone agar test, Hoffer’s alkaline Test and Keto-lactose Test). On the basis of morphological properties, rhizobial colonies on yeast extract mannitol agar (YEMA) medium were round mucoid and milky white with convex elevation and smooth surface. Under microscopic examination, all the bacterial isolates appeared as Gram negative, rod shaped and motile. Biochemical characterization of rhizobium isolates showed positive reaction with catalase, oxidase, starch hydrolysis, nitrate reduction, gelatinase, lysine decarboxylase and urease while most of the rhizobium isolates have negative reaction with        methyl red and Voges Proskauer. The strains showed resistance to the antibiotics such as erythromycin, fusidic acid, methicilin and pencicillin. All the isolated bacterial strains were susceptible to novobiocin and tetracycline. Out of 19 isolates, six isolates showed resistance to Chloramphenicol. All of these tests confirmed that findings of the present study have been isolated Rhizobium species.