Biomass partitioning and canopy architecture of six German winter wheat cultivars released between 1895 and 2002

Abstract

Breeding has significantly improved grain yields in winter wheat (Triticum aestivum L.). Grain yield improvements were previously attributed to changes in biomass partitioning and canopy architecture, largely based on measurements at single time points such as flowering or maturity. However, comprehensive physiological data covering the growth of modern and historic cultivars throughout the growing season remain rare. This study investigated how breeding progress influenced canopy structure and biomass partitioning across six German winter wheat cultivars released between 1895 and 2002. Field experiments were conducted over two seasons to measure aboveground biomass, root biomass, and canopy traits such as leaf area index (LAI) and specific leaf area (SLA) at multiple stages. Root biomass was assessed using large pots that were buried within an already sown field. Results showed differences in biomass partitioning patterns between cultivars and a trend toward a lower root to shoot ratio at anthesis in modern cultivars. Compared with modern cultivars, historic cultivars displayed larger flag leaves, a higher maximum LAI around flowering and a larger SLA, but similar light extinction coefficients. Significant season effects were observed, with reduced shoot biomass and increased root allocation at flowering in 2023, a year with a hot and dry spring, particularly in older cultivars. Yield increases were most strongly associated with harvest index, alongside faster phenological development and changes in biomass allocation across developmental stages. These findings provide stage-specific insights into cultivar physiology that might help in guiding future breeding strategies.