Stress-induced deeper rooting introgression enhance wheat yield under terminal drought

Water deficit is one of the major environmental constraints on wheat production. This situation is increasingly aggravated by climatic variation and poses a serious challenge to global food security. Recent progress in breeding efforts to improve wheat yields under drought has been mainly directed towards above-ground traits. Roots traits are closely associated with various drought adaptability mechanisms, but the genetic variation underlying these traits remains untapped, even though they hold tremendous potential to improve crop resilience. Here, we examined this idea by re-introducing ancestral wild wheat alleles and studied its impact on root architecture diversity under terminal drought stress. We compared a wild emmer introgression line (IL20) and its drought-sensitive recurrent parent (Svevo) using an active sensing electrical resistivity tomography approach under field conditions. IL20 exhibited greater root elongation under drought, which resulted in higher root water uptake from deeper soil layers. This advantage initiates at the pseudo-stem stage and increases during the transition to the reproductive stage. The increased water uptake promoted higher gas exchange rates and enhanced grain yield under drought. Overall, we show that this presumably ‘lost’ drought-induced mechanism of deeper rooting profile can serve as a breeding target to improve wheat productiveness under changing climate.