A GENETIC-LINKAGE MAP OF DURUM-WHEAT

A genetic linkage map of tetraploid wheat [Triticum turgidum (L.) Thel l.] was constructed using segregation data from a population of 65 rec ombinant inbred lines (RILs) derived from a cross between the durum wh eat cultivar Messapia and accession MG4343 of T. turgidum (L.) Thell. ssp dicoccoides (Korn.) Thell. A total of 259 loci were analysed, incl uding 244 restriction fragment length polymorphisms (RFLPs), one PCR ( polymerase chain reaction) marker (a sequence coding for a LMW (low-mo lecular-weight) glutenin subunit gene located at the Glu-B3 locus), se ven biochemical (six seed-storage protein loci and one isozyme locus) and seven morphological markers. A total of 213 loci were mapped at a LOD greater than or equal to 3 on all 14 chromosomes of the A and B ge nomes. The total length of the map is 1352 cM and the average distance between adjacent markers is 6.3 cM. Forty six loci could not be mappe d at a LOD greater than or equal to 3. A fraction (18.6%) of the marke rs deviated significantly from the expected Mendelian ratios; clusters of loci showing distorted segregation were found on chromosomes 1B, 3 AL, 4AL, 6AL and 7AL. The durum wheat map was compared with the publis hed maps of bread wheat using several common RFLP markers and general features are discussed. The markers detected the known structural rear rangements involving chromosomes 4A, 5A and 7B as well as the transloc ation between 2B-6B, but not the deletion on 2BS, This map provides a useful tool for analysing and breeding economically important quantita tive traits and for marker-assisted selection, as well as for studies of genome organisation in small grain cereal species.