RELATIONSHIPS BETWEEN THE CHROMOSOMES OF AEGILOPS UMBELLULATA AND WHEAT

A comparative genetic map of Aegilops umbellulata with wheat was const ructed using RFLP probes that detect homoeoloci previously mapped in h exaploid bread wheat. All seven Ae. umbellulata chromosomes display on e or more rearrangements relative to wheat. These structural changes a re consistent with the sub-terminal morphology of chromosomes 2 U, 3 U , 6 U and 7 U. Comparison of the chromosomal locations assigned by map ping and those obtained by hybridization to wheat/Ae. umbellulata sing le chromosome addition lines verified the composition of the added Ae. umbellulata chromosomes and indicated that no further cytological rea rrangements had taken place during the production of the alien-wheat a neuploid lines. Relationships between Ae. umbellulata and wheat chromo somes were confirmed, based on homoeology of the centromeric regions, for 1 U, 2 U, 3 U, 5 U and 7 U. However, homoeology of the centromeric regions of 4 U with wheat group-6 chromosomes and of 6 U with wheat g roup-4 chromosomes was also confirmed, suggesting that a re-naming of these chromosomes map be pertinent. The consequences of the rearrangem ents of the Ae. umbellulata genome relative to wheat for gene introgre ssion are discussed.