干旱区生态环境知识资源中心

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 NaCI 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 Glade close to type strains Ensifer medicae and Ensifer melifoti 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. meliloti and E. medicae which indicates their evolution 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.

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