Evaluation of the Global Durum Panel (<em>Triticum turgidum</em> ssp. <em>durum</em>) for Wheat Streak Mosaic Virus Resistance, Winter Survival, and Seed Characteristics

The majority of durum wheat (Triticum turgidum spp. durum; AABB; 2n=4x=28) is predominantly grown in the northern Great Plains of the United States, and is used in the production of semolina, a coarse flour that makes pasta and couscous. Durum has been widely regarded for being more tolerant to abiotic stress, due to its ability to withstand drought and high temperatures. In this thesis, we conducted greenhouse, field, and lab studies, for the traits wheat streak mosaic virus (WSMV), winter survival, and single kernel characteristics of the Global Durum Panel version 2 (GDPv2 n = 976), a panel representing a high level of diversity. Utilizing the phenotypic data we collected coupled with 90K SNP data, we further performed Genomic Wide Association Study (GWAS) analyses to identify marker trait associations for each phenotype. In the case of WSMV, only a single durum entry was found to have a low disease score, highlighting a need for further research in wild relatives for introgression of resistance genes. For the winter survival trait, 19% of the panel survived the winter, where 3% of the entries were characterized at survival rates of ≥ 70%, indicating these lines could be grown in a Nebraska winter wheat cropping system. The GWAS results for winter survival ratings indicated 12 quantitative trait loci (QTL) at chromosomes 1A, 2A, 2B, 3A, 3B, 4A, 4B, 5A, and 7A. GWAS analysis was performed on a subset of entries with winter survival ratings of ≥ 20% (n = 208). The phenotypes collected were hardness index, single kernel weight and kernel size using the Single Kernel Characterization System (SKCS) and endosperm chalky content was characterized using a flatbed color image scanner. GWAS for each trait indicated that there are multiple QTLs for each trait. The cumulative research findings of this thesis sheds light on durum wheat’s extreme susceptibility to WSMV and further highlights the potential of durum wheat’s cultivation in a winter wheat cropping system. Advisors: Katherine Frels and Jeffrey Boehm, Jr.