Estudios citogenéticos en híbridos interespecificos de Amaranthus.

EDUARDO J. GREIZERSTEIN Y LIDIA POGGIO

DARWINIANA

INSTITUTO DE BOTÁNICA DARWINION

Lugar: Buenos Aires; Año: 1992 vol. 31 p. 159 - 165

0011-6793

ABSTRACT: Greizerstein, E. J. & Poggio, L. 1992. Cytogenetic studies in six interspecific hy¬brids of Amaranthus (Amaranthaceae). Darwiniana 31: 159-165. Meiotic behavior of six interspecific hybrids was studied. The hybrids between species with n = 16 chromosomes showed regular meiosis with 16 bivalents; they varied considerably in pollen vi¬ability (5-60%). These results suggest the existence of cryptic structural hybridity. The structural divergence between A. quitensis (2n = 32) and the grain species A. caudatus (2n = 32) and A. hypochondriacus (2n = 32) is higher than that observed between A. quitensis (2n = 32) and the wild species A. hybridus (2n = 32). The pollen viability of the A. hybridus (2n = 32) x A. quitensis (2n = 32) hybrid is lower than that observed in its parents; these results suggest that there is some degree of reproductive isolation and consequently they are not co-specific. The A. cruentus (2n = 34) x A. quitensis (2n = 32) hybrid showed 15II + 1III in all cells. This fact supports the hypothesis that n = 17 would have its origin in a n = 16 ancestor through primary trisomy. The hybrid be¬tween A. hybridus (2n = 32) and A. spinosus (2n = 34) showed 8II + 17I as the most frequent configuration, suggesting that both species would-have a x = 8 genome with high homeology; moreo¬ver this fact, together with the secondary association found in all studied species and hybrids, sup¬ports the hypothesis that present species (X1 = 16) of the genus Amaranthus (2n = 32) are polyploids (basic number x = 8) and that consequently n = 16 is a derived basic number. The number n = 17 (X2 = 17) would have appeared later by primary trisomy. The study of A. dubius (2n = 64) x A. spinosus (2n = 34) hybrid suggest that there would be autosyndelic pairing between A. dubius chro¬mosomes and allosyndetic pairing between A. dubius and A. spinosus chromosomes. It is therefore concluded that A. dubius would be an allooctoploid that would have stabilized at 2n = 64 by an aneuploid process, being A. spinosus one of its parental species.