Identification and molecular characterization of root nodule microsymbiont of Trigonella foenumgraecum L. Growing in different soils from Western Rajasthan, India

Abstract

Aim: To identify and characterize N fixing root nodule bacteria (RNB) of Trigonella foenum-graecum (TFG) growing in soils collected from different districts of Western Rajasthan. Methodology: Selected RNB strains were characterised phenotypically and molecular phylogeny was studied using their 16S rRNAand symbiosis-related gene sequences. Results : The 31 selected RNB strains formed three groups on the basis of colony characteristics. The TFG-RNB strains showed metabolic diversity in terms of carbon utilization and intrinsic antibiotic resistance, with few strains showing NaCl tolerance up to 4% and growth on a wide range of pH (4-11). In 16S rRNA gene phylogeny six (TFG22, TFG33, TFG53, TFG59, TFG64 and TFG66) selected strains clustered in a novel clade close to type strains Ensifermedicae and Ensifermeliloti forming two distinct 16S rRNA types. The symbiotic (nodA and nifH) and 16S rRNA phylogenies of TFG-Ensifer strains were in congruence. The sym genes of TFG strains have intermediate sequences diversified from closely related E. melilotiand E. medicae which indicates theirevolution through horizontal gene transfer. Interpretation: Nitrogen fixing TFG-Ensifer strains isolated from Western Rajasthan are potentially novel and showing plant growth promoting activity therefore can be used as inoculants in agricultural fields of semi-arid regions.