Chromosome analysis of the Arachis pintoi x A. repens (Leguminosae) hybrid by classical and molecular cytogenetics

Karyotypic analysis was carried out in the parental species, Arachis pintoi and A. repens, and in the interspecific hybrid. The three entities presented the same karyotype formula (18m+2sm) and one satellited chromosome pair. This satellited pair presented one pair of proximal CMA(+) bands which corresponded to heterochromatin associated with NORs, in coincidence with the localization of 45S DNAr loci. The number of identified DAPI(+) bands ranged between three and five pairs. The number of 5S DNAr loci was variable, with four in A. pintoi, two in A. repens and an intermediate number of three in the hybrid. The results showed chromosome similarities between parental species, indicating that they constitute a natural group. On the other hand, the three entities presented a normal meiotic behavior, with the formation of ten bivalents (10 II) in metaphase I and regular segregation of homologs in anaphase I. Arachis pintoi, A. repens and the interspecific hybrid presented a percentage for pollen viability of 97.43%, 99.4% and 97.53%, respectively. Our results indicate that the pairing and segregation of chromosomes during meiosis and the pollen formation were normal, and thus that the lack of seed production is not due to meiotic irregularities.