Improving Sustainability of Perennial Ryegrass (Lolium perenne) Seed Production: Integrated crop management practices and the development of a novel metabolomics-assisted technique to select for resistance to rust (Puccinia) pathogens

University of Minnesota Ph.D. dissertation. May 2014. Major: Applied Plant Sciences. Advisors: Eric Watkins, Nancy Ehlke. 1 computer file (PDF); xviii, 165 pages.This project focused on three main areas of study which will have a significant impact on the perennial ryegrass seed industry and end users. They are: 1) the effects of alternative nitrogen and growth regulator management practices including their interaction on crop agronomic characteristics and stem rust , 2) the effect of seeding rate and row spacing and their interaction with N rate on crop agronomic characteristics, competition with weeds, and stem rust and 3) the development of a novel breeding strategy (metabolomics-assisted selection) to help with faster and more accurate selection for crown rust resistance in perennial ryegrass. To study the effects of alternative growth regulator and nitrogen management practices, experiments were conducted during 2009 and 2010. Three N application methods (single, two-split, and three-split), five growth regulators (split and single applications of prohexadione Ca or trinexapac ethyl) and two spring N rates (56 or 100 kg N ha-1) were evaluated in a split-split plot design. Seeding rates (SRs) and row spacing widths (RSWs) in perennial ryegrass seed production are variable and the impacts of these factors on perennial ryegrass seed yield and plant growth characteristics are not well characterized. Experiments were conducted during 2010 and 2011 where five seeding rates [1.3, 2.6, 5.2, 7.8, and 10.4 kg PLS (pure live seed) seed ha-1], three row spacing widths (10, 20, and 30 cm), and three N rates (67, 112, and 157 kg N ha-1) were evaluated. The goal of metabolomics-assisted selection research was to detect a set of metabolic biomarkers to be used for fast and accurate selection of crown rust resistant perennial ryegrass genotypes. These chemical biomarkers will serve as a "metabolic fingerprint" associated with crown rust resistance in perennial ryegrass. Termed metabolomics-assisted breeding, this technique will lead to faster cultivar development and ultimately reduce fungicide use, making perennial ryegrass seed production a more profitable, marketable and sustainable option for farmers in rural communities in northern Minnesota as well as the Pacific Northwest and Canada