Identifying QTL for grain protein content independent from grain yield-related traits in durum wheat

Grain protein content (GPC) is a crucial quality trait determining the nutritional, rheological, and end-use properties characteristics of wheat. Breeding programs for GPC were hindered by complex genetic control, the strong influence of environmental factors, and the negative correlation between GPC and grain yield. To identify stable quantitative trait loci (QTL) associated with increased GPC without decreasing grain yield, a recombinant inbred lines population of durum wheat was genotyped with a 25K SNP array and evaluated for GPC and yield-related traits in four field trials. Six QTL for GPC were identified on chromosomes 1B, 2B (two loci), 4B, 5A, and 6A, consistently expressed across environments, four of which had antagonistic effects on grain yield per spike (GYS). Two QTL (QGpc.mgb-5A and QGpc/TKW.mgb-2B.2) on 2B and 5A chromosomes were independent of GYS variations and could be used in marker-assisted selection (MAS) for GPC improvement. Identifying and utilizing beneficial QTL/genes for wheat improvement requires careful consideration of the inverse relationship between GPC and yield-related traits, and phenotypic data collected across multiple environments. MAS or genomic selection techniques can effectively target favorable alleles for GPC enhancement while minimizing the impact on grain yield.