Newer wheat cultivars achieved greater yield and water productivity through root and canopy synergies in the North China Plain

Selecting high water productivity wheat cultivars is an ideal strategy to maintain grain yield under water limited environments. However, the evolutionary and physiological-ecological mechanisms underlying high-yielding and water-efficient traits in wheat remain poorly understood. A three-year field experiment (2020–2023) was conducted in the North China Plain, encompassing three irrigation environments (W0: rainfed; W1: irrigation at jointing and W2: irrigation at both jointing and anthesis), and 14 wheat cultivars released between 1976–2016. The purpose was to identify morpho-physiological differences in grain yield and water productivity with cultivar replacement. Grain yield and water productivity increased by 0.41–0.75 % yr −1 and 0.43–0.76 % yr −1 with cultivar replacement under different irrigation environments. Compared to 1970s cultivars (JM 1 and JM 2), those released in the 2010s (JM 585, JM 518 and JM 325) showed a 70.05–117.96 % increase in leaf area index and a 32.61–44.70 % increase in post-anthesis dry matter accumulation . Additionally, the ratio of green to yellow leaf dry weight increased by 30.77–105.12 %. Wheat cultivars released in the 2010s delayed senescence of the surface 0–30 cm root system under W0 and W1, resulting in a 23.82 % and 0.73 % increase respectively in total root length post-anthesis, while reducing total root length by 22.29 % under W2. Structural equation modeling indicated that grain yield and water productivity were positively affected by leaf area index and the ratio of leaf area to total root length at late grain filling period. Newly released wheat cultivars improve grain yield and water productivity through improving root adaptation and optimizing root-canopy synergies post-anthesis. These findings offer critical insights for breeding and selecting wheat cultivars with high water efficiency, supporting sustainable agriculture in water-limited regions. • Cultivar replacement increased grain yield and water productivity by an average of 0.58 % yr. −1 and 0.60 % yr. −1 . • Breeding increased post-anthesis leaf area index by 70.05–117.96 %. • Breeding resulted in an average 75.38 % increase in leaf area/total root length at grain filling period. • Balancing root-canopy dry matter distribution improved grain yield and water productivity.