Root traits of dryland winter wheat (Triticum aestivum L.) from the 1940s to the 2010s in Shaanxi Province, China

Eight cultivars of winter wheat (Triticum aestivum L.) adapted to dryland conditions that have been historically planted in Shaanxi Province, China, were grown in plots with irrigation and drought treatments during the growing seasons of 2010–2012 to characterize the changes in root system traits and water use efficiency during the replacement of cultivars. The results showed that the overall root size of dryland wheat cultivars in Shaanxi Province changed with the planting decade. Modern cultivars developed after the 2000s had larger root surface areas than older cultivars under the drought treatment, especially at soil depths of 0–40 cm. However, the total water consumption throughout the stages showed no obvious changes among cultivars. The yield significantly increased with the planting decade, and the water use efficiency showed an average increase of 47.07% from the earliest to the most recent studied cultivar. Water stress promoted larger root sizes than those found in the irrigation treatment, especially at maturity. A trend toward a lower stress susceptibility index was observed over the decades, indicating that the sizes of modern cultivar roots increased less in the drought treatment than in the irrigation treatment. Both the roots and yields of the landrace cultivar from the 1940s showed low sensitivity to drought and better adjustment between the different water conditions. The study revealed that (1) modern wheat cultivars in Shaanxi Province possess higher water use efficiencies and decreased drought resilience and (2) the selection of ideal root traits should consider stable yields under different water conditions.