High-resolution radiation hybrid map of wheat chromosome 1D

Physical mapping methods that do not rely on meiotic recombination are necessary for complex polyploid genomes such as wheat (Triticum aestivum L.). This need is due to the uneven distribution of recombination and significant variation in genetic to physical distance ratios. One method that has proven valuable in a number of nonplant and plant systems is radiation hybrid (RH) mapping. This work presents, for the first time, a high-resolution radiation hybrid map of wheat chromosome 1D (D genome) in a tetraploid durum wheat (7: turgidum L., AB genomes) background. An RH panel of 87 lines was used to map 378 molecular markers, which detected 2312 chromosome breaks. The total map distance ranged from ~3,341 [cR.sub.35,000] for five major linkage groups to 11,773 [cR.sub.35,000] for a comprehensive map. The mapping resolution was estimated to be ~199 kb/break and provided the starting point for BAC contig alignment. To date, this is the highest resolution that has been obtained by plant RH mapping and serves as a first step for the development of RH resources in wheat.