Rheological Performance of Wholemeal Flour from Bread Wheat Under Contrasting Agro-Ecological Conditions: A Multi-Environment Analysis of Mixolab® 2 Parameters and Genotypic Stability

Bread wheat technological quality is jointly influenced by genotype, environment, and their interaction (G × E). Although Mixolab® has been used to characterize rheological variation among wheat genotypes, its combined application with stability analysis remains limited in Moroccan multi-environment trials. Rheological variability and relative stability were evaluated using wholemeal flour from 13 bread wheat varieties grown across three contrasting agro-ecological zones in Morocco. Under a fixed hydration level of 60%—rather than the sample-specific hydration used in the standard ICC 173 procedure—nine Mixolab® 2 parameters (C1–C5, α, β, γ, and mixing stability time) were measured. Two-way ANOVA, REML-based BLUPs, principal component analysis (PCA), and inter-environment stability indices were applied to evaluate varietal performance and relative stability. Highly significant effects (p < 0.001) of genotype, environment, and G × E were observed for all parameters. Under fixed hydration, the observed responses may reflect differences in flour composition, water-binding properties, and dough development at a common water level. Environmental contributions were largest for α and mixing stability time, whereas genotype-associated contributions were largest for C4 and C5. The first two principal components explained 72.6% of the total variability and identified three rheological groups under fixed hydration conditions: low-consistency genotypes, varieties with balanced rheological profiles, and starch-oriented genotypes. Within the three-environment, single-season network, Kenz, Najia, Khadija, Malika, and Ibtissam showed the lowest inter-environment variation, whereas Lina and Irchad showed the greatest. Whether these rankings remain consistent under the standard ICC 173 sample-specific hydration procedure remains unknown. These results illustrate the potential of combining Mixolab® 2 parameters with mixed-model and stability analyses to characterize rheological patterns under fixed hydration conditions. Additional environments and cropping seasons are required before broad adaptation or environment-specific recommendations can be made.