Genetic mapping within the wheat D genome reveals QTL for germination, seed vigour and longevity, and early seedling growth

Quantitative trait loci (QTL) controlling germination, seed vigour and longevity, and early seedling growth were identified using a set of common wheat lines carrying known D genome introgression segments. Seed germination (capacity, timing, rate and synchronicity) was characterized by a standard germination test, based either on the 1 mm root protrusion (germination sensu stricto) or the development of normal seedlings. To quantify seed vigour, the same traits were measured from batches of seed exposed for 72 h at 43A degrees C and high (ca. 100%) humidity. Seed longevity was evaluated from the relative trait values. Seedling growth was assessed both under non-stressed and under osmotic stress conditions. Twenty QTL were mapped to chromosomes 1D, 2D, 4D, 5D, and 7D. Most of the QTL for germination sensu stricto clustered on chromosome 1DS in the region Xgwm1291-Xgwm337. A region on chromosome 7DS associated with Xgwm1002 harboured loci controlling the development of normal seedlings. Seed vigour-related QTL were present in a region of chromosome 5DL linked to Xgwm960. QTL for seed longevity were coincident with those for germination or seed vigour on chromosomes 1D or 5D. QTL for seedling growth were identified on chromosomes 4D and 5D. A candidate homologues search suggested the putative functions of the genes within the respective regions. These results offer perspectives for the selection of favourable alleles to improve certain vigour traits in wheat, although the negative effects of the same chromosome regions on other traits may limit their practical use.