HOMOLOGY BETWEEN THE A AND B GENOMES OF BROMUS PUMPELLIANUS SSP. DICKSONII

Abstract

Chromosome pairing in the tetraploid F1 hybrid (AAAB) from B. erectus (AAAA) × B. pumpellianus ssp. dicksonii (AABB) was very complete. The pairing in a 61-cell sample from one hybrid plant was 1.97 IV + 0.51 III + 8.43 II + 1.75 I. Three cells containing a pentavalent, hexavalent or an octavalent were also found. The pairing results show that the A genomes of B. erectus and B. pumpellianus ssp. dicksonii are homologous, and that the A and B genomes are nearly homologous with few gross structural changes. Bromus pumpellianus ssp. dicksonii should be considered a segmental allotetraploid with predominant bivalent pairing.