IDENTIFICATION AND HIGH-DENSITY MAPPING OF GENE-RICH REGIONS IN CHROMOSOME GROUP-1 OF WHEAT

We studied the distribution of genes and recombination in wheat (Triti cum aestivum) group 1 chromosomes by comparing high-density physical a nd genetic maps. Physical maps of chromosomes 1A, 1B, and 1D were gene rated by mapping 50 DNA markers on 56 single-break deletion lines. A c onsensus physical map was compared with the 1D genetic map of Triticum tauschii (68 markers) and a Triticeae group 1 consensus map (288 mark ers) to generate a cytogenetic ladder map (CLM). Most group 1 markers (86%) were present in five clusters that encompassed only 10% of the g roup 2 chromosome. This distribution may reflect that of genes because more than half of the probes were cDNA clones and 30% were PstI genom ic. All 14 agronomically important genes in group 1 chromosomes were p resent in these clusters. Most recombination occurred in gene-cluster regions. Markers fell at an average distance of 244 kb in these region s. The CLM involving the Triticeae consensus genetic map revealed that the above distribution of genes and recombination is the same in othe r Triticeae species. Because of a significant number of common markers , our CLM can be used for comparative mapping and to estimate physical distances among markers in many Poaceae species including rice and ma ize.