Simultaneous Discrimination of the Three Genomes in Hexaploid Wheat by Multicolor Fluorescence in Situ Hybridization Using Total Genomic and Highly Repeated DNA Probes

Common wheat, Triticum aestivum, is an allohexaploid species consisting of three different genomes (A, B, and D). The three genomes were simultaneously discriminated with different colors. Biotinylated total genomic DNA of the diploid A genome progenitor Triticum urartu, digoxigenin-labeled total genomic DNA of the diploid D genome progenitor Aegilops squarrosa, and nonlabeled total genomic DNA of one of the possible B genome progenitors Ae. speltoides were hybridized in situ to metaphase chromosome spreads of Triticum aestivum cv. Chinese Spring. For detection, only two fluorochromes, fluorescein and rhodamine, were used. The A, B, and D genomes were simultaneously detected by their yellow, brown, and orange fluorescence, respectively. The genomic fluorescence in situ hybridization pattern of chromosome 4A of cv. Chinese Spring wheat showed that the distal 32% of the long arm was derived from a B genome chromosome. Furthermore, by using two highly repeated sequence probes, pSc 119.2 and pAsl, and two fluorochromes simultaneously, we were able to identify all B and D genome chromosomes and chromosomes 1A, 4A, and 5A of wheat.