Giemsa C-banding in two polyploid, South American Hordeum species, H. tetraploidum and H. lechleri, and their aneuploid hybrids with H. vulgare

The karyotype of H. tetraploidum (2n = 4x = 28) had eight metacentric, three submetacentric, and three SAT-chromosome pairs. The karyotype of H. lechleri studied in a polyhaploid (2n = 3x = 21) had thirteen metacentrics, three submetacentrics, and five SAT-chromosomes, one more SAT-chromosome than previously reported.

The C-banding patterns of both species were rather similar, having smaller to larger bands with no preferential disposition. The two species are referred to sections Stenostachys and Critesion, respectively, but similarities among C-banded karyotypes of the two species and some North American taxa of the same sections suggest a rather close relationship and support that the biological basis for their classification with different sections is questionable.

C-banding patterns identified the chromosomes of parental genomes in interspecific hybrids between the two species and H. vulgare. The hybrids were stably aneuploid. Both had lost and acquired H. vulgare chromosomes. Thus, somatic elimination of chromosomes was combined with multiplication of chromosomes.

The observations of stably aneuploid hybrids have implications for the exploitation of alien germplasm. The activity of non-H. vulgare SAT-chromosomes was partly suppressed in the hybrids, indicating incomplete differential amphiplasty.