QUANTITATIVE TRAIT LOCI INFLUENCING GRAIN PROTEIN-CONTENT IN TETRAPLOID WHEATS

Seed storage protein content of durum wheat (Triticum turgidum var. du rum) has an important effect on nutritional value and pasta-making cha racteristics. The objective of this study was to determine by associat ion with genetic markers the number, chromosomal location, and magnitu de of effect of quantitative trait loci (QTLs) controlling protein con centration in kernels. A set of 65 recombinant inbred lines (RIs) was developed by single seed descent from a cross between cultivated durum wheat cv. 'Messapia' (low protein content) and accession MG4343 of th e wild tetraploid wheat var. dicoccoides (high protein content). This population was characterized for eight morphological, six storage prot ein, one isozyme and 124 RFLP loci. Field trials were conducted in one location in 1993 and two locations in 1994. QTLs were mapped by regre ssion analysis on each marker locus for each location and for the aver age across environments. A total of six putative QTLs were located on chromosome arms 4BS, 5AL, 6AS, 6BS and 7BS. The number and size of QTL s detected varied across environments. The marker with the highest r(2 ) value per QTL in each environment and across environments was chosen for a multiple linear regression analysis, which explained 49.2-56.4% of the phenotypic variation for protein content. Only some of the mar kers were found to be negatively associated with plant grain yield and /or seed weight in one or two of the environments.