Molecular cytogenetic characterization and comparison of the two cultivated species (Fabaceae).

The two cultivated (Adanson, 1763) species, (N. J. von Jacquin, 1788) A. P. de Candolle, 1825 and (Linnaeus, 1753) A. P. de Candolle, 1825 are closely related based on morphological and molecular phylogenetic data. However, the similarities and differences in genome organization between them have not been evaluated at molecular cytogenetic level. Here, detailed karyotypes of both species were constructed using combined PI and DAPI (CPD) staining, rDNA-FISH and self-genomic hybridization (sGISH). For further comparison, comparative genomic hybridization (cGISH) and sequence analysis of 5S rDNA were applied. Their chromosomes were accurately identified by sGISH and rDNA-FISH signals. Both species had the karyotype formula 2n = 22 = 18m + 4m-SAT, but the karyotype of was shorter and more asymmetric than that of . They displayed similar CPD bands at all 45S rDNA sites and centromeres. had ten centromeric 5S rDNA loci and two SC (secondary constriction)-associated 45S rDNA loci. had nine centromeric and one interstitial 5S loci, two SC-associated and one proximal 45S loci. Their sGISH signal patterns displayed both basic similarities and distinct differences. Reciprocal cGISH generated prominent signals in all pericentromeric regions and 45S sites. There was lower level of sequence identity of the non-transcribed spacer between their 5S rDNA repeats. These data confirmed the evolutionary closeness between and and demonstrated obvious differentiation between their genomes, and supported the opinion that is more advanced in evolution than .