Genome wide association study of free asparagine content in durum wheat grain

Acrylamide (AA), a molecule classified as probable human carcinogen [1,2], has been detected in a wide range of foods [3]. AA is generated during Maillard cascade reactions [4,5,6] and free asparagine (fAsn) content has been identified as a key factor in wheat derivatives. The aim of the project is to study the natural variation for fAsn levels in durum wheat (Triticum turgidum L. ssp. durum (Desf.)) grains to identify candidate genes controlling fAsn seed content. To this purpose, 215 durum wheat genotypes, (including 195 durum wheat landraces), were selected from the international Global Durum Panel (GDP) [7], whose collection was previously genotyped with Illumina iSelect 90K SNP array technology. Population structure analysis indicated that the selected panel maintained a high level of genetic variability, comparable to that observed for the original population. The clustering analysis identified four groups, matching the geographic region of origin of the genotypes. Pairwise marker correlations (r2 values) were calculated on the SNPs dataset using TASSEL5[8]. Linkage Disequilibrium Decay was calculated with a distance of 4.4 Mbp. These 215 genotypes were sown in single location for three years. The field experiments were established in a randomized complete block design (Agricolae3.1, R package) with five check cultivars that were each replicated seven times. The quantification of fAsn levels in whole-grain samples from the first two years of field trials was obtained using an enzymatic/spectrophotometric method [9]. The analysis showed the presence of a good variability for fAsn in this population. A preliminary multi-locus genome-wide association study was performed, and SNPs associated with grain fAsn content were found. In addition, 100 genotypes were selected from first year field trial to be investigated by High Resolution 1H-NMR (Proton Nuclear Magnetic Resonance) spectroscopy, to monitor metabolite composition. This work was partially funded by the European Regional Development Fund under the ROP of the Lombardy Region ERDF 2014-2020--Axis I "Strengthen technological research, development and innovation"--Action 1.b.1.3 "Support for co-operative R&D activities to develop new sustainable technologies, products and services"--Call Hub.