Screening of Diazotrophic Bacterial Communities from Wild Rice (Oryza indica) and Cultivated Rice (Oryza sativa) and their Plant Growth Promoting Activities

A study was undertaken to screen the free living, culturable diazotrophic bacteria from wild rice (Oryza indica) and cultivated rice (Oryza sativa) and their plant growth promoting activities. Out of forty eight diazotrophic isolates, thirty eight isolates recorded positive growth in Nfree medium which were further analyzed for total nitrogen and ammonia. Based on total nitrogen and ammonia production, twenty eight diazotrophic isolates were selected for nitrogenase activity. The highest nitrogenase activity was exhibited by isolate GDR16 (413456.6 nm of ethylene mg^-1 protein^-1 hr). For PGPR activity 11 isolates from O.indica and 9 isolates from O.sativa with elite nitrogenase activity were selected for PGPR as well as mineral solubilization studies. Out of these 20 diazotrophic isolates, 11 isolates showed IAA production. The maximum amount of IAA was produced by CBE1 (35.5 1.14g ml^-1). The highest amount of GA was produced by GDR13 (21.70.19 g ml^-1), followed by GDR 7 which produced 18.40.23 g ml^-1. The maximum siderophore production was recorded with CBE1 (43.94 0.64g mg^-1 dry weight of cell of catechol type). With respect to mineral solubilization, 17 were able to solubilze the insoluble phosphorus and 7 were able to solubilze the zinc. The results of the present study showed the diazotrophic bacteria associated to both wild and cultivated rice and it having variety of plant growth promoting substances in considerable amounts apart from diazotrophy.