Wild emmer introgressions alter root-to-shoot growth dynamics in response to water stress

Water deficit is a major limiting factor for wheat (Triticum sp.) development and productivity. One approach to increase water stress adaptation in wheat is incorporating novel alleles from the drought-adapted wheat progenitor, wild emmer (T. turgidum ssp. dicoccoides). We explored this idea in the context of vegetative growth by examining the phenotypic consequence of a series of wild emmer (acc. Zavitan) introgressions into elite durum wheat (cv. Svevo) under water-limited conditions. Using image-based phenotyping we cataloged divergent (from Svevo) growth responses to water stress ranging from high plasticity to high stability among the introgression lines. We identified an introgression line (IL20) that exhibits a highly plastic response to water stress by shifting its root-to-shoot biomass ratio for detailed characterization. By combining genotypic information with root transcriptome analysis, we propose several candidate genes (including a root-specific kinase) that can confer the shoot-to-root carbon resource allocation in IL20 under water stress. Discovery of high plasticity trait in IL20 in response to water stress highlights the potential of wild introgressions for enhancing stress adaptation via mechanisms that may be absent or rare in elite breeding material.