Mapping and validation of QTkw.cau-3DL, a major QTL controlling thousand-kernel weight in wheat.

Key message: A novel major QTL, QTkw.cau-3DL, for thousand-kernel weight has been identified on the wheat chromosome arm 3DL and enhances grain yield by 6.2% under field conditions. Increasing kernel weight is an effective way to improve yield potential in wheat. The identification of major quantitative trait loci (QTL) for kernel weight, without negative effects on other yield-related traits, is crucial for continuous yield improvement. We developed a population of F₆ recombinant inbred lines from Jimai 120 × Jimai 325 and identified eight QTL for thousand-kernel weight, kernel length, and kernel width across five environments. The population was genotyped using Wheat15K SNP arrays and QTL analysis found that one QTL, QTkw.cau-3DL, on the chromosome arm 3DL consistently showed major effects on TKW and KL in five field experiments. This QTL accounted for up to 16.43% and 13.87% of phenotypic variation, respectively. QTkw.cau-3DL was confined to a 5.72-Mb (3.48 cM) interval between 554.39 Mb and 560.11 Mb. This QTL was validated in a pair of NILs and in a new population. QTkw.cau-3DL increased kernel weight per spike without any negative effect on heading data, plant height, spike length, spikelet number per spike, or kernels number per spike. It increased grain yield by 6.2% under regular field production conditions. Haplotype analysis and geographical distribution in a nationwide collection of 630 wheat cultivars showed that QTkw.cau-3DL has not been widely deployed in Chinese wheat breeding programs. QTkw.cau-3DL is a novel QTL for increasing TKW through increasing KL; therefore, it is an important locus for enhancing wheat grain yield. The tightly linked, user-friendly markers developed in this study should facilitate map-based cloning and marker-assisted selection of the QTL in wheat breeding programs.