Genetic Loci in Wheat Associated with High Grain Zinc Content in PBW343/Kenya Swara Recombinant Inbred Lines

Low content or deficiencies of essential micronutrients in staple food can result in micronutrient malnutrition. CIMMYT is engaged in enhancing the grain zinc (Zn) content of high yielding wheat germplasm under the HarvestPlus initiative of CGIAR consortium. We determined grain zinc content (GZnC) in a recombinant inbred line (RIL) population from the cross PBW343/Kenya Swara in replicated trials grown for two years in Zn enriched field at Cd. Obregon, Mexico. An integrated genetic map with 1133 loci (DArT and SSR markers) covering all 21 wheat chromosomes was constructed and used for QTL analysis. Two large effect QTLs were stably detected for increasing GZnC in both environments on chromosomes 2Bc (centromeric region) and 3AL (long arm). The two QTL individually explained about 10 to 15% of the total phenotypic variation. The 2Bc QTL from PBW343 had pleiotropic effect; it significantly increased the thousand-kernel weight (TKW), thousand-kernel volume (TKV) and thousand-kernel zinc weight (TKZnW). This is first proof of concept evidence where pleiotropic QTL enhances grain Zn and grain size simultaneously, contradicts the perception of small grains tends to load more Zn. The 3AL QTL from Kenya Swara increased grain zinc content only. Another QTL on 1BL was also identified from PBW343 for increasing TKW, TKV and TKZnW in significant levels. The RILs that showed significantly enhanced grain Zn content than either parent along with desirable agronomic traits can be utilized by breeding programs to continue making progress in developing high grain Zn varieties.