Evolution of root hydraulic properties of wheat with breeding and its influence on root water uptake: insights from a field experiment and modelling

Abstract

Root water uptake is a pivotal process in the regulation of water movement within the soil-plant-atmosphere continuum. At a specific atmospheric demand, root water uptake is determined by the architecture of the root system and the hydraulic properties of individual roots and root segments. In agricultural settings, root traits are affected by management practices, including breeding. Specifically for wheat, the most important European crop, a decrease in root system size has been observed in modern varieties compared to historical ones1, and differences in root hydraulic properties between cultivated and wild species have been documented2. However, an assessment on the long-term evolution of root hydraulic properties with breeding is still absent.  Here, we investigated the effect of breeding on root hydraulic properties of wheat and its implications for root water uptake at the plant scale. For this, an experiment encompassing six wheat cultivars spanning over a century of breeding history was conducted. We measured the number of root axes (crown roots and seminal roots) of plants grown in the field during the tillering phase (BBCH <30) and the root hydraulic conductivity of young plants grown in hydroponics (<12 days, no crown roots), using the pressure chamber technique.Average root hydraulic conductivity (per root surface area) did not differ among cultivars, but a pronounced decrease in the number of root axes was observed in the most recent cultivars. Based on these observations, simulations with the whole-plant 3-D model CPlantBox were performed, indicating a higher whole-root system conductance in the oldest cultivars at the end of the tillering phase, associated with a higher number of tillers and root axes. This suggests an evolution of wheat cultivars towards more conserving root water uptake strategies, a feature of special importance under water-limited conditions. References 1Zhao et al. (2005). 10.1111/j.1744-7909.2005.00043.x 2Fradgley et al. (2020). 10.1007/s11104-020-04585-2