Novel bacterium Rhizobium undicola isolated from the upland cultivated rice Oryza sativa L. promoting plant growth

Abstract

A novel endophytic nitrogen-fixing bacterium identified as Rhizobium undicola (Ouran110) on the basis of 16S rRNA gene sequence analysis was isolated from surface-sterilized roots of upland rice Oryza sativa L. var. Narendra Dhan 118. The diazotrophic nature of the bacterium was established by its close homology with typical diazotrophic bacteria and further confirmed by the amplification of nifH gene. Amplification of nodC confirmed that the strain could be a legume symbiont and this was further ascertained by the nodulation of the strain with Phaseolus vulgaris and Glycine max. Endophytic colonization ability was ascertained by molecular tagging with gfp/Gusa fused to a constitutive promoter followed by inoculation onto rice seedlings in axenic condition. Microscopic observation confirmed colonization of gfp/gus-tagged Ouran110 in the intercellular spaces of vascular zones of rice roots. Inoculation of R. undicola (Ouran110) with rice plants resulted in significant increase in plant growth promoting traits suggesting implications of this endophytic bacterium as bio-fertilizer in sustainable rice production agriculture.