DISSECTING THE TETRAPLOID WHEAT ROOT GROWTH ANGLE QTLOME: A KEY COMPONENT OF DROUGHT STRESS RESILIENCE

Development of drought-resilient durum wheat varieties under climate change requires an indepth understanding of the complex genetic traits i.e., root growth angle (RGA) which anticipates the root system architecture. RGA QTLome was characterized in the Global Durum Genomic Resource (GDGR, https://wheat.pw.usda.gov/GG3/global_durum_genomic_resources) germplasm comprising a wide array of Tetraploid Germplasm Collection (TGC, Maccaferri et al. 2019, Nature Genetics) and Global Durum Panel (GDP, Mazzucotelli et al. 2020, Frontiers) containing ca. 500 durum cultivars, ca. 1,000 T. turgidum landraces- and ca. 500 domesticated and wild emmer, all genotyped with the Illumina iSelect 90K wheat SNP array. RGA ranged from 12.98˚ to 160.82˚ with a h2 of 0.82. Genome-Wide association study (GWAS) identified 7 QTLs in cultivars and 13 QTLs in landraces, among which three major QTLs on 2A, 6A and 7A chromosomes were consistently found, accounting for a total of 23.5% and 14.5% R2 in cultivars and landraces, respectively. Notably, QRGA.ubo-6A.2 on chromosome 6A showed the largest R2 effect (13.4% in cultivars and 8.6% in landraces). Haplotype analysis found narrow RGA common in North American, French, CIMMYT and ICARDA ‘70s cultivars, likely inherited from landraces in the Horn of Africa, Ethiopia. In contrast, the QRGA.ubo-6A.2 shallow haplotype was mainly found in the CIMMYT’60-SVEVO and CIMMYT’80-ALTAR_C84 lineages, probably derived from Turkey-to-Fertile Crescent, South- West Asian, Iranian T. turanicum and transcaucasian landraces and emmer. Cultivars contrasting in RGA due to the cumulative effects of 2A, 6A and 7A QTLs are currently being evaluated for the phenotypic beneficial effects on drought resilience at CIMMYT, ICARDA and at University of Queensland. Gene ontology showed significant enrichment of biological process involving organophosphate metabolism, response to osmotic stress and cytoskeleton organization. Furthermore, multi-omics analyses predicted TraesCS6A02G385500, TRAESCS6A02G390700 and TRAESCS6A02G390600 as candidate genes in QRGA.ubo-6A.2 QTL intervals. Haplotype-tagging KASP® markers have been developed for validation and the recent progress including the cloning of QRGA.ubo-6A.2 will be presented. Acknowledgements: Research supported by “Rooty”, Rooty-A root ideotype toolbox to support improved wheat yields (IWYP), “CerealMed”- Enhancing diversity in Mediterranean cereal farming systems (PRIMA2019), and “INNOVAR” - Next generation variety testing for improved cropping on European farmland projects (H2020 FP7), NEWRoots - Evaluation & cloning of a major root angle QTL for a sustainable production in durum wheat (PRIN-2022).