GENOME RELATIONS OF AGROPYRON SERICEUM,HORDEUM JUBATUM AND THEIR HYBRIDS

Cytogenetic investigation of microsporogenesis in Agropyron sericeum, Hordeum jubatum, their spontaneous hybrid, Agrohordeum pilosilemma, its amphiploid, and the backcross of the amphiploid to A. sericeum, B₁, elucidated the genome relationships of A. sericeum and H. jubatum. The tetraploid parental species share a partially homologous genome which affects the pairing relationships evidenced in their hybrids. The genome formulae assigned to these plants are: A. sericeum, A“A”BB; H. jubatum, AAA'A‘; Agrohordeum pilosilemma, AA'A“B; the amphiploid, AAA'A‘A”A“BB; and B₁, AA'A”A“BB. Observed pairing configurations were compatible with the expected maximum pairing configurations predicted under the assumption of genetic control of pairing with dosage effects. This is interpreted as further support for the hypothesis that pairing in the hybrids of H. jubatum is controlled by the A genome, one dose of A allowing homeologous pairing and two doses of A promoting homeologous association.