Molecular Analysis of Diazotrophic Rhizobacteria in Rice: A Study on Diversity and Nitrogen Fixation Efficiency

Two traditional rice varieties, Sataria and Kartki were collected from specific fields located in Madhubani district of North Bihar. A wide range of nitrogen-fixing bacteria (diazotrophs) were isolated from roots of these two rice varieties using enrichment in nitrogen-free semisolid media;Using ribosomal RNA-directed oligonucleotide probes, 53 isolates from Sataria and 137 isolates from Kartki rice variety were identified as eubacteria. Out of these 190 isolates, the majority of them (183) were identified as α-, β- or γ- proteobacteria. Using group specific oligonucleotide probes, 14 isolates were assigned to α-, 137 to β- and 32 to γ-subgroup of proteobacteria. Five different endophytic diazotrophic rhizobacteria (Herbaspirillum seropedica, Gluconobacter diazotrophicus, Azospirillum brasilense, Burkholderia cepacia and Pseudomonas sp.) were inoculation of axenically grown Kartki rice seedlings and their impact on growth and yield was analysed. Among all five diazotrophic bacteria, B. cepacia showed highest increase in plant growth and grain yield.