A durum wheat intervarietal genetic and physical map based on SSR and TRAP markers

The durum wheat is one tetraploide species (genomes AABB) cultivated mainly in the Mediterranean regions, Canada, USA, Argentina and India. In spite of the importance in the worldwide production of wheat, this species has received less attention than common wheat by investigators. Recently genetic maps based on molecular markers (RFLP, AFLP, microsatellites, etc) have been developed and published for the various species of cereals including durum wheat. The availability of genetic maps and phenotypic data of segregant populations allow to localize and map agronomically important genes, and to identify closely associated molecular markers to be used in of marker-assisted selection (MAS) programs and for the positional cloning. Objective of the present work was to develop a durum wheat intervarietal genetic and physical map based on genomic microsatellite markers (gSSR) as anchor chromosome loci, EST-derived microsatellite markers (EST-SSR), and TRAP (Target Region Amplification Polymorphism) markers for the saturation of uncovered chromosome regions. The up to now map comprises 2 morphologic markers (awn colour, bla, and ear glaucousness, W1), two seed storage protein markers (Gli-A2, Gli-B2), 285 SSR and 303 TRAP markers. The JoinMap software grouped the loci in 26 linkage groups, of which 17 assigned to the of the A and B genome chromosomes; the remaining 9 group will be assigned to chromosomes by physical mapping with deletion lines. The number of mapped markers per chromosome ranged from a minimum of 9 markers for the chromosomes 5A and 5B to a maximum of 39 markers for the chromosome 1B, with an average of 25 markers for chromosome. With the integration of the TRAP markers, the basic map accounted for a total length of 1,468.5 cM, with an average density of one marker per 4.8 cM. A higher percentage (57.8%) of the markers has been found localized on the B genome chromosomes, in comparison to 42.2% distributed on the A genome chromosomes. The B genome accounted for 803.3 cM of genetic distance; the A-genome basic maps spanned 665.2 cM. The comparison of the marker order on the chromosomes in the various published maps was made by the common genomic SSR; out of 133 mapped gSSR markers, three markers were found to be localized on different chromosomes.