Modern wheat breeding selection synergistically improves above- and belowground traits.

The root system is a fundamental organ for the uptake of water and nutrients and defines interactions with the local environment (Calleja-Cabrera et al. 2020; Siddiqui et al. 2021). As such, it plays a vital role in meeting the increasing global food demand and has been proposed as the critical target for the second Green Revolution (Herder et al. 2010; Schneider and Lynch 2020; Ober et al. 2021; Maqbool et al. 2022). Bread wheat (Triticum aestivum L.) is the most widely grown crop (FAO 2023). Over the past century, wheat breeding has remarkably increased yield by selecting for aboveground traits (Tadesse et al. 2019; Voss-Fels et al. 2019; Pronin et al. 2020). A few studies have investigated the effects of wheat breeding on the root system with limited historical varieties, but they did not draw a consistent conclusion (Qin et al. 2019; Zhu et al. 2019; Fradgley et al. 2020). Therefore, whether and how modern breeding changed the root system remains largely unknown, limiting our understanding of the roles of the root system in the past wheat improvement and how to improve the root system efficiently in the future.