Abstract
Polymorphic wheat varieties consist of intra-varietal biotypes differing in traits expressed under contrasting growing conditions.This study evaluated the responses of winter wheat biotypes to environmental variation and their complementarity as a mechanism contributing to yield stability.Two Kazakh winter wheat varieties, Qarasay and Naz, were differentiated into biotypes based on differences in gliadin composition.The biotypes were evaluated under contrasting growing conditions in southern and southeastern Kazakhstan during 2016-2017 to characterize their phenotypic plasticity and adaptive responses.Morphological and agronomic traits were analyzed to assess differences in biotype performance and complementarity.Qarasay biotypes differed in productive tillering and main spike length, exhibiting asynchronous expression of these traits across environments.In contrast, Naz biotypes showed similar patterns of yield formation.GGE biplot analysis revealed intra-varietal complementarity within Qarasay, with biotype 1 contributing to higher mean grain yield and biotype 2 contributing to greater yield stability.Qarasay biotypes also differed in the accumulation of individual protein fractions but possessed identical high-molecularweight glutenin subunit compositions, suggesting that their coexistence within a polymorphic variety would not compromise bread-making quality.These results demonstrate that complementarity among intra-varietal biotypes may enhance yield stability and adaptability of polymorphic wheat varieties while maintaining grain quality.