Genetic Dissection of Grain Zinc, Iron, and Yield Traits in a CIMMYT Bread Wheat mapping population to Support Biofortification Breeding

Zinc and iron deficiencies represent significant global health challenges, with wheat biofortification emerging as a viable strategy to mitigate these issues. However, simultaneously enhancing grain zinc content (GZnC), grain iron content (GFeC), and yield-related traits remains a considerable challenge in wheat breeding. To elucidate the genetic basis underlying these traits, this study employed a population of 198 F₆ recombinant inbred lines (RILs) derived from a cross between the high-zinc/iron parent 'Manku' and the low-zinc parent 'Kachu' developed at CIMMYT, Mexico. The population was phenotyped for grain zinc concentration, grain iron concentration, heading date (DH), plant height (PH), thousand-kernel weight (TKW), and test weight (TW) over two growing seasons and genotyped by DArT-Seq platform. A total of 72 QTLs were identified by using the ICIM-ADD method and a multi-environment trait model, among which 23 were consistently detected by both methods, indicating their stable expression. Several major and stable QTLs were uncovered, including QDH.cim-5B and QDH.cim-7D for heading date, QTKW.cim-7B.2 for thousand-kernel weight, and QGZnC.cim-7D for grain zinc concentration. Notably, QTL clusters associated with zinc/iron content and yield traits were identified on chromosomes 2B, 5A, and 7D, suggesting potential for synergistic improvement in these genomic regions. Candidate gene prediction within six QTL intervals associated with zinc and iron content identified 17 genes potentially involved in zinc/iron transport or homeostasis, including zinc transporters, oligopeptide transporters, and glutathione S-transferases. Additionally, we selected 15 promising lines (e.g., KM_618, KM_633, KM_782, KM_791) that could be used for zinc and iron biofortification or for the simultaneous improvement of micronutrient content and yield. The stable QTLs identified in this study provide valuable theoretical foundations and genetic resources for the coordinated improvement of zinc/iron nutrition and yield in wheat.