A comparative Analysis of Primary and Specialized Metabolites in Durum Wheat Grains Reveals Striking Differences across Durum Emmer Wheat, Landraces and Modern Cultivars

A comprehensive profiling of primary and specialised metabolites was carried out on fifty durum wheat accessions of different geographical origin, including ancient emmer, traditional landraces and modern cultivars, grown in a single cropping season, at the same site, and under uniform agronomic management, to reduce within-trial environmental heterogeneity and avoid confounding between genotype and environment. Proteins, gluten, and starch were analysed as primary metabolites, while free and bound phenolic acids, carotenoids, and anthocyanins were identified and quantified as specialized metabolites. The results revealed that domestication and modern breeding practices have resulted in a reduction in phenolic acid levels, particularly the bound form of ferulic, vanillic and p-coumaric acids, coupled with an increase in carotenoid content, especially β-carotene and lutein. However, no notable variations were observed in macronutrient composition across the germplasm categories. Although an increase in carotenoid content may offer nutritional benefits, the concurrent reduction in the overall content of phenolic bioactive compounds observed over time raises concerns about genetic erosion. The higher levels of bound phenolic acids found in ancient spelt varieties, particularly p-coumaric and ferulic acids, support their use as valuable sources of genetic variation for biofortification strategies. The ancient and traditional wheat varieties included in this study could be incorporated into breeding programmes to improve the nutritional quality of modern durum wheat cultivars, particularly for use in Mediterranean diets.