MOLECULAR MAPPING OF WHEAT - HOMOEOLOGOUS GROUP-3

A prerequisite for molecular level genetic studies and breeding in whe at is a molecular marker map derailing its similarities with those of other grass species in the Gramineae family. We have constructed restr iction fragment length polymorphism maps of the A-, B-, and D-genome c hromosomes of homoeologous group 3 of hexaploid wheat (Triticum aestiv um L. em. Thell) using 114 F-7-8 lines from a synthetic X bread wheat cross. The map consists of 58 markers spanning 230 cM on chromosome 3A . 62 markers spanning 260 cM on 3B, and 10 markers spanning 171 cM on 3D. Thirteen libraries of genomic or cDNA clones from wheat, barley, a nd T. tauschii, the wheat D genome donor, are represented, facilitatin g the alignment and comparison of these maps with maps of other grass species. Twenty four clones reveal homoeoloci on two of the three geno mes and the associated linkages are largely comparable across genomes. A consensus sequence of orthologous loci in grass species genomes is assembled from this map and from existing maps of the chromosome 3 hom oeologs in barley (Hordeum spp.). T. tauschii, and rice (Oryza spp.). It illustrates the close homoeology among the four species and the par tial homoeology of wheat chromosome 3 with oat (Avena spp.) chromosome C. Two orthologous red grain color genes, R3 and R1, are mapped on ch romosome arms 3BL and 3DL.