DNA restriction fragment length polymorphisms: a strategy for genetic mapping of D genome of wheat

The use of restriction fragment length polymorphisms (RFLPs) as genetic markers in bread wheat, Triticum aestivum, and a wild wheat progenitor, Aegilops squarrosa, was investigated. The objectives were (i) to identify RFLP loci; (ii) to assign cDNA sequences onto specific chromosomes and chromosome arms; and (iii) to determine linkage relationships between RFLP loci. A low level of polymorphism was found, utilizing barley cDNA clones as probes, in hexaploid cultivated wheats. However, accessions of A. squarrosa revealed greater polymorphism. Wheat–barley alien addition lines were used to assign 17 cDNA sequences to specific chromosome groups and ditelosomic and nullisomic–tetrasomic wheat stocks were used to assign these sequences to specific chromosome arms. Of 16 sets of RFLP loci, excluding α-Amy-1 and α-Amy-2, 14 are new sets of loci marking 6 of the 7 homoeologous groups of wheat. The construction of a linkage map of chromosome 5D was initiated by analyzing a segregating F2 population between two homozygous accessions of A. squarrosa. A strategy using wheat aneuploids for chromosome arm location and a segregating A. squarrosa population for linkage measurement was demonstrated for mapping the D-genome chromosomes of wheat.Key words: genetic map, restriction fragment length polymorphisms, Triticum aestivum, Aegilops squarrosa, polyploidy.