Genetic dissection of tocopherol and phytosterol in recombinant inbred lines of sunflower through quantitative trait locus analysis and the candidate gene approach

Sunflower (Helianthus annuus L.) contains tocopherol, a non-enzymatic antioxidant known as lipid-soluble vitamin E, and phytosterol, with interesting properties, which can result in decreased risk of chronic diseases in humans and with several beneficial effects in plants. The genetic control of tocopherol and phytosterol content in a population of 123 recombinant inbred lines of sunflower was studied through quantitative trait loci (QTL) analysis using 190 simple sequence repeats and a gene-based linkage map. Seven experiments were conducted in different environments in France and Iran during 2007 and 2008. Each experiment consisted of three replications. Means over all environments were used for QTL mapping. Five QTL for total tocopherol content on linkage groups 1, 8, 10 and 14 accounted for 45% of phenotypic variation, whereas four QTL for total phytosterol content on linkage groups 1, 2, 16 and 17 explained 27% of the phenotypic variation. GST, PAT2, SFH3 and POD genes showed co-localization with QTL for total phytosterol content. SMT2 is also mapped on linkage group 17 near the QTL of total phytosterol content. Four candidate genes, VTE4, HPPD, GST and Droug1, exhibited co-localization with QTL for total tocopherol content. The candidate genes associated with tocopherol and phytosterol, especially HPPD, VTE4 and SMT2, could be used for alternation of the tocopherol and phytosterol content of sunflower seeds through the development of functional markers.