Harnessing Wild Wheat Root and Coleoptile Traits for DroughtResilient Wheat

Project Summary:

Drought is a major constraint to US (and global) wheat production, and breeding varieties with improved performance under water limitation is urgently needed. While both spring and winter wheat growth is affected by drought, some of the challenges are unique to winter wheat. Winter wheat productivity under drought is threatened at two critical stages: seedling establishment, warmer, drier fall conditions in the US Great Plains increasingly impair stand establishment, as coleoptiles shorten at elevated temperatures and fail to penetrate hard or crusted soils; and water acquisition during the growing season, as top soils dry, mechanical impedance to root growth increases, and metabolic cost of root tissue construction limits soil exploration. Root anatomical traits and coleoptile characteristics influence each of these constraints and can be optimized through wild-relative introgression.

Wild relatives of wheat, including Ae. tauschii and T. dicoccoides, are known for sharper root tips for hard soil penetration, smaller xylem vessels for water conservation, and reduced cortical and stele parenchyma for lower metabolic cost. They may also harbor allelic diversity for coleoptile length stability under elevated temperatures and superior coleoptile penetration strength. Our prior WGRC-funded Sharp Roots project (FY23) screened >250 WGRC introgression lines for root tip shape, identifying lines with significantly greater penetration of hard wax layers than modern bread wheat. Likewise, our preliminary
coleoptile studies across 50 winter wheat genotypes, including Ae. tauschii introgression lines (ILs) revealed substantial variability for coleoptile length at 15 °C and 25 °C and identified few genotypes with stable length and superior strength.

While building on the previous project by mapping the underlying genes for root tip sharpness, we also plan to harness wild wheat coleoptile properties for improved seedling establishment and root anatomical traits that collectively optimize root water economy. The project has three objectives: (1) genetic mapping of root tip sharpness: identifying genomic regions and SNP markers linked to sharper root tips using GWAS and biparental mapping; (2) screening drought-adaptive root anatomical traits: characterizing WGRC introgression lines for stele size, metaxylem vessel diameter, and cortical cell file number, with trait data cross-referenced against existing WGRC drought field performance; and (3) coleoptile length and strength evaluation: screening introgression lines for temperature-stable coleoptile length and penetration strength, including development of a computer-vision phenotyping pipeline.

This project directly addresses the WGRC FY26 priority on heat and drought stress by leveraging WGRC wild wheat germplasm and introgression lines to identify and transfer novel adaptive alleles for both belowground (root) and abo veground (coleoptile) traits critical for wheat performance under drought and heat. All trait data will be integrated with existing WGRC drought field records to validate agronomic relevance for industry partners and growers.