MOLECULAR MAPPING OF WHEAT - HOMOEOLOGOUS GROUP-2

A molecular-marker map of bread wheat having many markers in common wi th other grasses in the Gramineae family is a prerequisite for molecul ar level genetic studies and breeding in this crop species. We have co nstructed restriction fragment length polymorphism maps of the A-, B-, and D-genome chromosomes of homoeologous group 2 of hexaploid wheat ( Triticum aestivum L. em. Their) using 114 F-7 lines from a synthetic x bread wheat cross and clones from ii libraries. Chromosomes 2A, 2B, a nd 2D comprise 57, 60, and 56 markers and each spans about 200 cM. Com parisons between chromosomes are facilitated by 26 sets of homoeoloci. Genes mapped include a heterologous abscisic acid responsive locus cl oned as pBS128, the epidermal waxiness inhibitor W2(1), and two presum ed leaf rust and stem rust resistance genes. Anomalies suggesting ance stral rearrangements in chromosome 2B are pointed out and features of wheat group 2 chromosomes that are common to barley (Hordeum vulgare L .), rice (Oryza spp.), and T. tauschii are discussed.