Theses and Dissertations Collection

Wheat (Triticum aestivum L.), and barley (Hordeum vulgare L.) are two important small grains crops that fulfill important human caloric and nutritional requirements globally. More efficient small grain production systems are required to meet increasing grain demand while minimizing adverse environmental impacts associated with production. The purpose of this dissertation was to identify novel germplasm, traits, and associated quantitative trait loci (QTL) in the National Small Grains Collection (NSGC) through genome-wide association studies (GWAS). The specific objectives were to: 1) identify novel accessions and QTLs associated with dwarf bunt resistance; and 2) characterize barley accessions and identify QTLs associated with drought tolerance and agronomic traits. In objective 1, 292 winter bread wheat accessions were tested for dwarf bunt (Tilletia controversa J.G. Kühn) resistance over a three year trial period in Logan, UT. Ninety-eight accessions were identified as resistant with disease incidence ≤10%, of which 28 accessions were highly resistant with an incidence ≤1% across all three trials. Two genetic loci on chromosome 6D were found to be associated with resistance across three trials. In objective 2, 480 two-row spring barley accessions were assessed for terminal drought tolerance in Aberdeen, ID over two years. Agronomic traits including yield, test weight and protein were measured when the accessions were grown and harvested under regular irrigation and terminal drought treatments. Twenty accessions were highlighted for use in the malting industry and ten accessions were highlighted for use in the food industry. Fifteen genetic loci were associated with at least one agronomic trait across treatments. Accessions and genetic loci identified in these studies can be used to enhance locally adapted wheat and barley cultivars.