Chromosome pairing in octoploid F1 and octoploid amphiploid hybrids between Bromus inermis and B. pumpellianus

Abstract

Chromosome pairing in the amphiploid (8x) of 4x Bromus pumpellianus ssp. dicksonii × 4x B. inermis was compared with pairing in the F1 hybrids between natural octoploid cytotypes of B. inermis and B. pumpellianus and the octoploid parents. Predominantly bivalent pairing was found in both the amphioctoploid, octoploid F1 hybrids, and octoploid parents. Bivalent formation in the amphioctoploid could be based on chromosome differentiation between the tetraploid cytotypes of B. inermis and B. pumpellianus. These results suggest that the evolution of the octoploid cytotypes of B. inermis and B. pumpellianus could have involved hybridization of the tetraploid cytotypes.Key words: Bromus, chromosome pairing, octoploid, F1 hybrid, amphiploid.