Rapid identification and discrimination among Egyptian genotypes of Rhizobium leguminosarum bv. viciae and Sinorhizobium meliloti nodulating faba bean ( Vicia faba L.) by analysis of nodC, ARDRA, and rDNA sequence analysis

Abstract

Twenty-eight Rhizobium strains were isolated from the root nodules of faba bean ( Vicia faba L.) collected from 11 governorates in Egypt. A majority of these strains (57%) were identified as Rhizobium leguminosarum bv. viciae ( Rlv) based on analysis of a nodC gene fragment amplified using specific primers for these faba bean symbionts. The strains were characterized using a polyphasic approach, including nodulation pattern, tolerance to environmental stresses, and genetic diversity based on amplified ribosomal DNA-restriction analysis (ARDRA) of both 16S and 23S rDNA. Analysis of tolerance to environmental stresses revealed that some of these strains can survive in the presence of 1% NaCl and a majority of them survived well at 37 °C. ARDRA indicated that the strains could be divided into six 16S rDNA genotypes and five 23S rDNA genotypes. Sequence analysis of 16S rDNA indicated that 57% were Rlv, two strains were Rhizobium etli, one strain was taxonomically related to Rhizobium rubi, and a group of strains were most closely related to Sinorhizobium meliloti. Results of these studies indicate that genetically diverse rhizobial strains are capable of forming N 2-fixing symbiotic associations with faba bean and PCR done using nodC primers allows for the rapid identification of V. faba symbionts.