MORPHOLOGICAL, BIOCHEMICAL AND MOLECULAR CHARACTERIZATION OF SUMMER MUNGBEAN (Vigna radiata L. Wilczek.) RHIZOBIAL DIVERSITY

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Date
2013
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Punjab Agricultural University, Ludhiana
Abstract
The present investigation was carried out to study the morphological, biochemical and molecular characterization of summer mungbean (Vigna radiata L. Wilczek.) rhizobial diversity. Twenty three rhizobial isolates from soil and nodule samples of summer mungbean rhizosphere from different parts of Punjab were characterized on the basis of morphological and biochemical tests. The isolates were identified as fast growing rhizobia (Rhizobium sp.) and slow growing rhizobia (Bradyrhizobium sp.) on BTB medium. Maximum IAA was produced by Rhizobium sp. LSMR 19 (16.04 μgml-1) followed by LSMR 5 (15.85 μgml-1). The maximum P-solubilization was observed with LSMR 1 (6.11 mg 100 ml-1) on 12th day followed by LSMR 5 (5.57 mg 100 ml-1). Maximum resistance was observed with penicillin 93.1% followed by ampicillin 73.9%. About 65%, 56% and 91% were found positive for cellulase, protease and ACC deaminase respectively. Out of 23 isolates of summer mungbean 65% and 26% of isolates were siderophore and HCN positive, respectively. Eight potential isolates of Rhizobium sp. (LSMR 1, LSMR 5, LSMR 8, LSMR 9, LSMR 11, LSMR 19 and LSMR 23) and Bradyrhizobium sp. (LSMR 10) and reference strain M 1were evaluated for plant infectivity test in summer mungbean variety SML 668. LSMR 1, LSMR 19 and LSMR 23 emerged as effective strains for growth and symbiotic traits in summer mungbean. Genotypic diversity among all rhizobial isolates were evaluated using RAPD-PCR technique. Genotyping based on RAPD primers revealed that all the rhizobial strains converged into 5 distinct groups viz. G-1, G-2, G-3, G-4 and G-5. 100% similarity was observed between LSMR 21 and LSMR 6, LSMR 19 and LSMR 17 and four isolates (LSMR 7, LSMR 8, LSMR 9 and LSMR10) of summer mungbean rhizobia. LSMR 1, LSMR 19 and LSMR 23 were found very promising based on biochemical and functional traits and were genetically diverse showing 33 to 60% similarity. Thus the preliminary information generated in present study could be useful for selection of single strain representing one genetic group for extensive field evaluation.
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