Master of Science / Department of Agronomy / Allan K. Fritz / Drought is known to be one of the most limiting abiotic stresses for wheat (Triticum aestivum L.) production, not only in the Midwest, but throughout the world. It is a complex issue and one that is difficult to screen for when breeding for new varieties. Hybrid wheat is one possible tool for breeders to use in order to make genetic gains towards better tolerance. The effectiveness of hybrid wheat as a tool to address regular periods of drought is a topic of continual discussion. The purpose of this study was to perform a comprehensive screening for drought tolerance comparing two different experimental hybrid entries to their parents. The hybrids were selected based on their good performance under drought in prior field trials. Plants were grown in PVC columns containing sensors that monitored growth media water content and matric potential. All plants were grown equally until heading. Drought treatment began 10 days post anthesis. Plants were observed until senescence/maturity. Several different agronomic characteristics were measured along with physiological traits that have previously been linked to drought tolerance. After completion of the screening, it was observed that the hybrid entries tended to fall between the two parents for a majority of the measurements. When comparing the hybrids to the parents overall, at least one parent outperformed its hybrid in every category. Parent line Parent B was one of the highest ranking genotypes for all measurements. Different drought mechanisms were observed across genotypes upon completion of the treatment. Further research is necessary to understand the hybrid response to drought when compared to pure line varieties.

Planting date (PD), seeding rate (SR), genotype, and row spacing (RS) influence hard red spring wheat (HRSW, Triticum aestivum L. emend. Thell.) and soybean [Glycine max (L.) Merr.] yield. Evaluating HRSW economic optimum seeding rates (EOSR) is needed as modern hybrids may improve performance and have different SR requirements than cultivars. Two cultivars and five hybrids were evaluated in five North Dakota environments at two PDs and five SRs ranging from 2.22-5.19 million live seeds ha-1 in 2019-2020. Planting date, SR, and genotypes have unique yield responses across environments. Hybrid yield was the most associated with kernels spike-1 (r=0.17 to 0.43). The best hybrid yielded greater than cultivars in three environments. The EOSR ranged from 4.08-4.15 and 3.67-3.85 million seeds ha-1 for cultivars and hybrids, respectively. Hybrids are economical if seed prices are within $0.18 kg-1 of cultivars. In soybean, individual and synergistic effects of PD, SR, genotype relative maturity (RM), and RS on seed yield and agronomic characteristics, and how well canopy measurements can predict seed yield in North Dakota were investigated. Early and late PD, early and late RM, and two SRs (457 000 and 408 000 seed ha-1) were evaluated in 14 environments and two RS (30.5 and 61 cm) were included in four environments in 2019-2020. Individual factors resulted in 245 and 189 kg ha-1 more yield for early PD and late RM, respectively. The improved treatment of early PD, late RM, and high SR factors had 16% yield and $140 ha-1 more partial profit greater than the control. When including RS, 30.5 cm RS had 7% more yield than 61 cm RS. Adding 30.5 cm RS to the improved treatment in four environments resulted in 26% yield and $291 ha-1 more partial net profit compared to the control. A normalized difference vegetative index (NDVI) at R5 was the single best yield predictor, and stepwise regression using canopy measurements explained 69% of yield variation. North Dakota farmers are recommended to combine early PDs, late RM cultivars, 457 000 seed ha-1 SR, and 30.5 cm RS to improve soybean yield and profit compared to current management trends.