Diversity of Rhizobia Nodulating Faba Bean (Vicia faba) Growing in Egypt

摘要

The aim of this work was to characterize and to describe the diversity and phylogeny of rhizobial bacteria associated to nodules of faba bean in four different geographical regions of north Egypt. Eight rhizobial isolates from healthy faba bean roots were isolated. They were identified as Rhizobium leguminosarum morphologically. They showed sensitivity to Kanamycin, Neomycin and Sulphemethooxazole antibiotics. Mannitol was the best source of carbon source for their growth. However, two isolates Rl. 2 and Rl. 10 indicated better tolerance to high NaCl concentrations than the other isolates and their plasmid profiles contained additional large plasmid with molecular weight about 23 kb. A relationship between salt tolerance and extra plasmid was suggested. Analysis of similarity among rhizobial isolates by using the RAPD-PCR technique showed a high level of genetic polymorphism, grouping the rhizobial isolates into two different clusters. These clusters reflexed the similarity among genotype of isolates independent of their geographic locations. 16S rDNA sequences of three representing isolates were determined and were aligned and compared with the 16S rDNA sequences of other members of the family Rhizobiaceae available in the Gene Bank database. The obtained dendogram indicated that the isolates belonging to Rhizobium leguminosarum biovar viciaen.