Phenotypic variation and QTL analysis for oil content and protein concentration in bread wheat (Triticum aestivum L.)

The lipid content of wheat is small yet could potentially contribute to increased calorific value of grain delivered for livestock and human consumption. Breeding for greater oil content is required but there is little understanding of the extent or nature of genotypic variation for oil concentration in wheat. A diverse range of commercial and novel spring wheat germplasm was assessed in two years under favourable conditions to understand the extent of genetic variation for lipid content. Genotypic differences were modest in size (4.27–5.32 %) but repeatable across years (rₛ = 0.71, P < 0.01) reflecting a higher line-mean heritability (0.75). Commercial varieties were intermediate-to-high in their total lipid concentration (mean of 4.82 %) while taller, larger embryo genotypes tended to produce greater lipid concentrations (mean of 4.91 %). Genetic increases in embryo size were associated with moderate increases in oil concentration (rg = 0.38, P < 0.01) while grain yield and oil concentration were uncorrelated (rg = −0.15, P > 0.05). QTL mapping was undertaken in the CD87/Katepwa wheat population phenotyped for grain oil and protein concentration in two years. Both total grain lipid and protein concentrations varied significantly across progeny ranging from 3.87 to 5.77 and 11.3 to 15.6 %, respectively while the ranking of lines for oil content was high (rₛ = 0.72, P < 0.01) across the 2 years. Nine and 12 QTL were identified for grain lipid and protein concentrations, respectively, with many of the lipid QTL located on the group D chromosomes. Oil and grain protein concentrations were uncorrelated (rg = −0.18, P > 0.05). The identification of diverse wheat sources with higher oil content together with improved genetic understanding suggests potential for genetic improvement of oil content in the development of higher oil wheats.