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Localization of ribosomal genes by FISH and CMA+ heterochromatic regions in two forage species, Arachis pintoi Krapov. & W.C. Gregory and A. repens Handro (Leguminosae) and their interspecific hybrids.
PUCCIARIELLO, O.; ORTIZ, A.M.; FERNÁNDEZ, A; LAVIA, G.I.
Buenos Aires (Argentina)
Simposio; 6th International Symposium on the Molecular Breeding of Forage and Turf MBFT 2010; 2010
Instituto Nacional de Tecnología Agropecuaria
The section Caulorrhizae includes two stoloniferous Brazilian species, Arachis repens and A. pintoi. Both species are economically important legumes. A. pintoi is cultivated as high-quality forage, while A. repens is cultivated as ornamental turf and forage. In order to combine the forage characteristics of A. pintoi with the resistance to pest and diseases of A. repens , crosses between both have been carried out. Nevertheless, the plants obtained in such crosses did not produce seeds and at the present there is no evidence for the origin of this sterility. In an attempt to infer the homology degree between parental entities and to contribute to elucidations of the genomic constitution of the hybrid, this work presents the karyotype comparison between the three entities by classical and molecular cytogenetics. Both species, as well as the interspecific hybrid, revealed the same karyotype formula (18m+2sm) and a pair of satellited chromosomes. This pair showed a pair of proximal CMA+ bands in the three taxa, which correspond to heterochromatin associated with NORs, in coincidence with 45S rDNA loci. The number of identified DAPI+ bands varied between 3 and 5, not being possible to decide the exact number for each entity studied. The number of 5S rDNA sites varied between the taxa: four in >A. pintoi , two in A. repens and three in the hybrid. Our results evidenced that, despite the differences in the number of 5S rDNA sites, the parental species and the hybrid present a high chromosomal homology degree, because they have the same karyotype formula, number of satellited chromosome pairs, number and localization of CMA+ bands and 45S rDNA sites, thus indicating that A. pintoi and A. repens form a natural group.