The physical organization of Triticeae chromosomes.

Molecular cytogenetics combines molecular information of DNA sequences with their chromosomal organization. Genomic in situ hybridization using total genomic DNA as a probe is proving particularly useful to paint chromosomes originating from different genomes in hybrids, alloploid species and alien plant breeding lines. Both the numbers and morphologies of alien chromosomes or chromosome segments can be detected at metaphase and interphase. The method also gives considerable information about species relationships and the distribution of common or diverse DNA sequences between closely related species. Painted chromosomes can be followed through all stages of the cell cycle of somatic and meiotic division, providing new information about chromosome behaviour and pairing at meiosis. In situ hybridization with defined probes enables the physical location of particular DNA sequences to be examined along chromosomes and the analysis of the long range organization of specific chromosome regions. The generation of an integrated genetical, physical and functional map will be useful for the understanding of the organization and structure of the cereal genome.