We developed three sets of Near Isogenic Lines (NILs) for QTL/genes affecting grain yield components into elite wheat CIMMYT germplasm (Reedling and Kingbird). These NILs consist of a QTL on chromosome 5A which affects grain length through cell expansion, a QTL on chromosome 6A affecting grain width through cell division, and a mutant knockout allele of GW2-A increasing both grain width and length. Whereas the 5A effect is seen after anthesis, the effect of the GW2-A mutant allele is observed in ovaries before anthesis. We hypothesize that the introduction of these alleles into CIMMYT germplasm will enhance final yield and that their combination could lead to more stable yield given their complementary modes of action. To test this hypothesis, the 5A, 6A, and GW2-A NILs are being grown under four different contrasting environments: Irrigation (YP), Drought Stress (DT) (DRIP and surface irrigation) and Heat Stress (HS); at CIMMYT facilities in Ciudad Obregon, Sonora, Mexico. Parallel to this, field and greenhouse experiments are being conducted in UK spring wheat cultivar Paragon at the John Innes Centre (Norwich, UK). Phenological traits (developmental stages, yield component and grain quality traits) are being taken to assess how these QTL and genes affect final yield under contrasting environments. Future germplasm with novel allelic combinations is being generated in the hope of producing more stable yielding bread wheat cultivars. We will update the community on the most recent field results across sites.