Breeding and nitrogen management shape root morphology and water use efficiency in wheat in the Huang-Huai-Hai region of China

Background and Aims

The root system of wheat is crucial for soil moisture uptake, grain yield, and grain water use efficiency (WUEg). Genetic improvements and nitrogen (N) fertilization influence root morphology. Understanding how root systems have changed across wheat varieties under varying N conditions is critical for future breeding and nutrient management.

Methods

A two-year field experiment examined ten key winter wheat varieties released between 1940 and 2021 in the Huang-Huai-Hai region, China. Root architecture, distribution, evapotranspiration, grain yield, WUEg, and the water use efficiency of aboveground biomass (WUEp) were evaluated under normal (220 kg N ha⁻¹) and reduced (143 kg N ha⁻¹) N applications.

Results

WUEg improved progressively with variety release year under both N regimes, though the underlying mechanisms differed. Under reduced N, modern cultivars developed greater root length density in subsurface (20–40 cm) and deep (40–100 cm) soil layers, enhancing deep moisture uptake. Under normal N, root growth was concentrated in the topsoil (0–20 cm), enabling modern varieties to use soil moisture more effectively. Genetic selection has reduced pre-anthesis water use while increasing post-anthesis use, particularly in dry years.

Conclusion

The past eight decades of winter wheat breeding have increased grain yields and improved WUEg through deeper rooting, particularly under low N conditions.