RFLP markers and their applications in cereal breeding

Individual RFLP-based maps are currently available for the Triticeae species wheat, barley and rte. However, an aspect of genetic mapping that is becoming increasingly important is the identification of intergenomic relationships, both within polyploids and between related species. In hexaploid bread wheat, a comparative genetic map of the A. B, and D genomes has been constructed, which, to date, includes some 1000 loci. The map reveals a strong collinearity of the homoeologous wheat genomes, that is disrupted only by a few chromosomal translocations. Comparative genetic maps of the wheat and rye genomes were constructed using a set of low copy homoeologous probes, previously characterized and mapped in wheat. The wheat and rye maps differ by a number of evolutionary translocations involving chromosome arms 2RS, 3RL, 4RL, 5RL, 6RS, 6RL, 7RS and 7RL. The presence of inter- and intrachromosomal rearrangements between 'donor' and 'recipient' genomes has important consequences for the development of gene introgression strategies.