LAVIA Graciela Ines
Cytogenetic evidences on the evolutionary relationships between the tetraploids of the section Rhizomatosae and related diploid species (Arachis, Leguminosae)
ORTIZ, ALEJANDRA MARCELA; ROBLEDO, GERMÁN; SEIJO, GUILLERMO; VALLS, JOSÉ FRANCISCO MONTENEGRO; LAVIA, GRACIELA INÉS
JOURNAL OF PLANT RESEARCH
Rhizomatosae is a taxonomic section of theSouth American genus Arachis, whose diagnostic characteris the presence of rhizomes in all its species. Thissection is of particular evolutionary interest because ithas three polyploid (A. pseudovillosa, A. nitida and A.glabrata, 2n = 4x = 40) and only one diploid (A. burkartii,2n = 2x = 20) species. The phylogenetic relationshipsof these species as well as the polyploidy nature and theorigin of the tetraploids are still controversial. The presentstudy provides an exhaustive analysis of the karyotypesof all rhizomatous species and six closely related diploidspecies of the sections Erectoides and Procumbentesby cytogenetic mapping of DAPI/CMA heterochromatinbands and 5S and 18?26S rDNA loci. Chromosome bandingshowed variation in the DAPI heterochromatin distributionpattern, which, together with the number and distributionof rDNA loci, allowed the characterization of allspecies studied here. The bulk of chromosomal markerssuggest that the three rhizomatous tetraploid species constitutea natural group and may have at least one commondiploid ancestor. The cytogenetic data of the diploid speciesanalyzed evidenced that the only rhizomatous diploidspecies?A. burkartii?has a karyotype pattern differentfrom those of the rhizomatous tetraploids, showing that it is not likely the genome donor of the tetraploids and thenon-monophyletic nature of the section Rhizomatosae.Thus, the tetraploid species should be excluded from theR genome, which should remain exclusively for A. burkartii.Instead, the karyotype features of these tetraploids arecompatible with those of different species of the sectionsErectoides and Procumbentes (E genome species), suggestingthe hypothesis of multiple origins of these tetraploids.In addition, the polyploid nature and the group of diploidspecies closer to the tetraploids are discussed.