THE USE OF FLUOROCHROMES IN THE CYTOGENETICS OF THE SMALL-GRAINED CEREALS (TRITICEAE)

This paper describes some of the major advances that have been made in the cytogenetics of the small-grained cereals (Triticeae) using fluor ochromes to detect nucleic acids in situ. The method, widely known as fluorescence in situ hybridization, has made a contribution in several areas including (i) chromosome mapping programmes, and (ii) cereal br eeding programmes. Flow cytometry of cereal chromosomes has now been d eveloped for the generation of chromosome enriched libraries; these li braries will ultimately be of use in both the cereal mapping and breed ing programmes. Fluorescence in situ hybridization has also made a maj or contribution to the understanding of cereal genome structure by elu cidating the distribution of different classes of DNA sequence. By usi ng suitable nucleic add probes whole chromosomes can now be identified in interphase nuclei. The labelling patterns have revealed a structur ed arrangement of chromosomes at interphase. Not only are chromosomes organized but the ribosomal RNA genes also show structured patterns of condensation and expression. Progress in each of these areas has been rapid in recent years and this progress is described.