Cytogenetics of a Hordeum vulgare x Elymus patagonicus hybrid (n=4x=28).

Hordeum vulgare L. (2n=2x=14) was hybridized with Elymus patagonicus Speg. (2n=6x=42). The hybrid had 28 chromosomes, genomically represented as HSH1H2, and was perennial with a codominant phenotype. The chromosomes were meiotically associated as 19.6 univalents + 0.004 ring bivalents + 2.6 rod bivalents + 0.8 trivalents + 0.14 quadrivalents in 1,129 meiocytes, with a chiasma frequency of 4.77 per cell. The bivalent pairing presumably is an autosyndetic but modified expression of the H1H2 genomes of E. patagonicus, since ring bivalents were rare. This does not preclude the association of the H. vulgare H genome chromosomes with either H1 and/or H2 genomes of E. patagonicus to form bivalent or multivalent associations. A further evaluation of the genome homologies of H. vulgare, H. bogdanii, E. canadensis and E. patagonicus is proposed.