A Major QTL Cluster of Weak-Gluten on Wheat Chromosome 2D informs Marker-Assisted Selection

Weak-gluten wheat, characterized by low protein content (<11.5%), soft kernels, and weak gluten strength, serves as essential raw material for confectionery products. Despite growing market demand, wheat production over the world faces a critical shortage of high-quality weak-gluten wheat varieties due to insufficient understanding of the genetic architecture underlying key quality traits. Here, we address this knowledge gap through comprehensive quantitative trait locus (QTL) mapping of five critical quality parameters, namely grain protein content (GPC), wet gluten content (WGC), Zeleny sedimentation value (ZSV), test weight (TW), and grain hardness (GH), using a recombinant inbred line (RIL) population of 143 lines derived from the "Mianmai 902/Taichung 29" cross evaluated across three diverse environments. Leveraging the Wheat 55K SNP array, we constructed a high-density genetic map comprising 10,132 markers with an average interval of 1.34 cM, identifying 41 QTLs distributed across 16 chromosomes. Most significantly, we discovered a narrow 2.61 Mb interval on chromosome 2DL (34.43-37.04 Mb) containing two co-localized major-effect QTLs, QZStm.swust-2DL (30.28% PVE) and QGHtm.swust-2DL (29.70% PVE), that demonstrate exceptional stability across environments. Within this critical interval, we identified TraesCS2D01G077600LC.1 , a candidate gene encoding lysine synthase that may influence gluten properties through amino acid metabolism. Furthermore, our QTL dosage analysis revealed a quantitative relationship between quality-associated loci and phenotypic expression, enabling predictive breeding strategies. Based on Chinese national standards for weak-gluten wheat, we successfully screened four elite RIL lines (TM77, TM103, TM116, and TM149) that combine superior quality traits with favorable agronomic characteristics. This study provides the first comprehensive QTL atlas specifically for weak-gluten wheat quality traits, delivering validated molecular markers and breeding materials to accelerate the development of high-quality varieties addressing the growing confectionery wheat demand over the world.