A novel QTL carrying NB-ARC family genes enhances grain protein content without grain weight penalty in wheat (Triticum aestivum L.).

Wheat ( Triticum aestivum L .) is a global food crop with low protein content of 9-12%. Enhancing grain protein content (GPC) without compromising yield is challenging largely due to the negative correlation between yield and GPC. Genome wide DNA markers, high-throughput phenotyping, genome-wide association studies (GWAS), and QTL mapping have facilitated the identification of quantitative trait loci (QTLs). This study utilized a stable recombinant inbred line F _7-9 (RIL) population, genotyped via high-depth genotyping by sequencing (GBS), and conducted multi-environmental trials to identify stable QTLs for GPC. In contrast to the inverse relationship of GPC and thousand grain weight (TGW), the RIL population showed positive correlation of 0.143 (P<0.001) with TGW. The RIL population also showed significant genetic variation in GPC, with a heritability of 0.72, and identified ten QTLs for GPC on chromosomes 2B, 5B, 5A, 4B, and 1D. Among these, QGPC.nabi-2B.2 and QGPC.nabi-5B.1 were identified as major and stable QTLs. Precise mapping of QGPC.nabi-2B.2 identified NB-ARC domain-containing proteins as potential candidate genes for GPC regulation. Three SNPs from the QGPC.nabi-2B.2 region were converted to Tetra-ARMS-PCR markers. Subsequently these markers were used to validate in Indian wheat varieties and in a genetically different RIL population. This study provides a foundation for further research into the genetic regulation of GPC in wheat and suggests that NB-ARC genes could play a significant role in improving GPC, potentially enhancing wheat's nutritional quality without yield penalty.