LAUSR

Common wheat breeding programs prioritize the development of high grain protein content (GPC) varieties, as GPC influences milling efficiency and end-use quality. However, the molecular basis of protein and gluten accumulation in wheat grains remains insufficiently understood, particularly regarding genetic differences between spring and winter types. We analyzed 170 winter wheat varieties from diverse domestic and international breeding programs cultivated in the European part of Russia over two growing seasons. Genome-wide association study identified 26 markers linked to GPC and 23 to gluten content (p < 0.001), with the strongest associations on chromosomes 4A and 2D. Variation in NAM-A1 also significantly affected GPC: varieties with the NAM-A1d allele showed lower protein content than NAM-A1a/c carriers (p < 0.01). We combined associations identified here with our previous GWAS results for GPC in spring wheat and further compared them with 17 additional studies including both spring and winter varieties. This analysis highlighted loci on chromosomes 3DL, 5AL, and 6AS (confirmed in at least two previous studies) for marker-assisted selection to improve grain quality. The distribution of loci showed no clear distinction between spring and winter wheat, suggesting that, despite environmental and developmental differences, the genetic basis of protein accumulation is largely shared.