Dissertation - Open Access
Doctor of Philosophy (PhD)
James G. Ross
Sixty-nine genotypes, including 60 from the variety Saratoga smooth bromegrass, three from South Dakota 7 smooth bromegrass, and two each of reed canarygrass, orchardgrass, and creeping meadow foxtail as check species were selected for regrowth from a source nursery containing over 37,000 genotypes. In addition, four genotypes of Saratoga with poor regrowth capability were selected as checks. These 73 genotypes were placed in a greenhouse environment to evaluate digestibility (IVDMD), and other characteristics. After three harvests, 34 genotypes were vegetatively propagated in a field experiment to determine regrowth capabilities. NCE rates were not correlated highly with yield in the greenhouse and were not used in making selections. The 34 selected genotypes included 32 from the Saratoga variety and one each of orchardgrass and reed canarygrass. Highly significant differences among genotypes were found for forage yield as well as for other plant characteristics in each separate environment. The relative importance of each component of yield was determined from the greenhouse data. In addition to these genotypes, three synthetics representing different responses to day length as well as superior regrowth potential were tested under field conditions for water use efficiency. Each of the three synthetics significantly exceeded Saratoga in yield over three cuttings in 1973. Also, two of the three synthetics were significantly higher in water use efficiency than the Saratoga control, and the third was slightly below the value required for significance. A correlation of .94 between yield and water use efficiency was found in each of two experiments indicating that water use efficiency could be predicted from yield. Significant differences among in vitro dry matter digestibility of selected genotypes were obtained for each of two cuttings in 1972 and for the first two cuttings of 1973. Significant differences among IVDMD of selected genotypes were not obtained for the third or fourth cutting of 1973. IVDMD was not used in making selections. On the basis of yield, water use efficiency, and seed production, seven genotypes were selected for use in two synthetics. These synthetics will be tested, and if either is found to be outstanding, will be released as a new variety. Other studies have involved determining the effects of smooth bromegrass pathogens on the in vitro dry matter digestibility of forage. Some reduction in in vitro dry matter digestibility was caused by Helminthosporium bromi in both the field and greenhouse. Bromegrass mosaic virus had no effect on digestibility of infected leaves.
Library of Congress Subject Headings
South Dakota State University
Gross, Delmer F., "Improving Water Use Efficiency of Smooth Bromegrass by Selecting for Regrowth" (1974). Electronic Theses and Dissertations. 5531.