Chromosome pairing failure in an intersectional amphiploid of Bromus altissimus × B. arvensis

Abstract

An intersectional F1 hybrid between Bromus arvensis and B. altissimus was made with the aid of embryo culture. The hybrid nature of the F1 and the amphiploid were confirmed by karyotyping root-tip cells. Following Giemsa banding, the chromosomes of B. arvensis stained darker than those of B. altissimus. Very little chromosome pairing was observed in the F1 hybrid (11.60 I + 1.08 II + 0.10 III). Chromosome pairing in the amphiploid (2n = 28) varied from almost complete pairing to very little pairing in different samples. The chromosome pairing indicated that very little homology exists between the genomes of B. altissimus and B. arvensis. Pairing failure in the amphiploid may result from the action of pairing control genes which are strong enough to prevent homologous pairing but which are variable in expression because of a sensitivity to endogenous and exogenous factors.Key words: Bromus, amphiploid, chromosome pairing, differential staining.