Responsive root traits and mitigating strategies for wheat production under single or combined abiotic stress

The frequency of abiotic stress impairing wheat root growth and yield production has been increasing with global warming. Diverse root traits have been widely targeted to improve wheat adaptivity to different abiotic stress, but most research has been conducted under controlled environments with a single stress factor, hindering transferability to fields conditions with multiple stresses. It is essential to distinguish the valuable root traits for both individual and combined abiotic stresses, and identify agronomic practices that can mitigate the detrimental effects on wheat production. This review summarizes morphological, physiological and anatomical root traits of wheat under stresses of drought, soil compaction, nitrogen (N) and phosphorus (P) deficiency, and waterlogging. Variations of root traits are further discussed under the co-occurrence of these abiotic stresses. In general, thick wide-angle seminal roots, deep sparse roots, and lengthy laterals roots are superior root traits under the stress combinations of drought combined with either soil compaction, N deficiency, or P deficiency. Dense adventitious, thin and sparse roots, and lengthy laterals with aerenchyma formation are superior root traits under the stress combinations of waterlogging combined with either soil compaction, N deficiency, or P deficiency. Wheat production loss from multiple stress conditions can be relieved by optimal crop and soil management strategies, including fertigation and subsurface drainage. Future development of wheat production should focus on taking advantage of adaptative root traits and agronomic optimization.