Harnessing genetic variation for grain quality from diverse wheat landraces

The grain quality traits of protein content, grain weight and size are socially and economically important for wheat (Triticum aestivum) breeding. Modern wheat germplasm has limited genetic variation for vital traits, including grain quality, underscoring the need to investigate ancestral varieties/landraces for beneficial allelic diversity. Here, we develop a reliable and sensitive single-seed hyperspectral imaging-based phenotyping platform to quantify grain protein, weight and size in 827 diverse wheat landraces, achieving improved predictive accuracy (R² = 0.91) vs previous methods. We identified novel genetic variants (or loci) for grain protein content and its heterogeneity between individual grains in a genotype, and grain weight, and validated them through bi-parental linkage mapping. Many loci we report are rare and absent from modern breeding germplasm. Beneficial haplotypes at these loci improved mean protein content and homogeneity without compromising grain weight; these haplotypes represent valuable genetic variation for agriculture. We identify a stable locus on chromosome 6A contributing to protein heterogeneity within single grains, suggesting homogeneity in protein content could be a selectable trait for breeding. Our findings demonstrate how integration of advanced phenotyping into breeding strategies can harness untapped genetic diversity for grain quality improvement in wheat, providing an opportunity to enhance grain nutritional value.