Biomass Yield Evaluation for Switchgrass Breeding: Seeded Swards vs. Transplanted Plots Yield Different Results
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Biomass Yield Evaluation for Switchgrass Breeding: Seeded Swards vs. Transplanted Plots Yield Different Results Michael D. Casler 1 Received: 4 February 2020 / Accepted: 26 October 2020 # This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply 2020
Abstract Switchgrass (Panicum virgatum L.) is undergoing intensive development as a biomass crop to support the production of energy from perennial grasslands. Plant breeding and selection represent a significant component of this development effort, requiring breeders to evaluate large numbers of genotypes and families for performance under real-world field conditions. Experimental unit size, shape, and interplant spacing can vary widely both within and across breeding programs, and there is some evidence that experimental units established from seedling transplants are poorly predictive of biomass yield in seeded swards. The purpose of this study was to determine the relationships among five types of experimental units, three based on transplanted seedlings (spaced plants, row plots, and simulated sward plots) and two based on seeded rows (bordered and unbordered sward plots). Nine switchgrass populations were evaluated with or without nitrogen fertilizer under all five plot types. Simulated sward plots had the lowest predictive value for biomass yield of sward plots. Spaced plants and row plots had greater predictive ability than simulated swards, but they accounted for less than 50% of the variability, suggesting that biomass measurements on these types of plots should not be considered as the same trait measured on seeded sward plots, especially considering the fact that the conditions of interplant competition are drastically different between these groups of plot types. Whereas biomass yield on a perhectare basis would be an appropriate trait name for seeded swards, plot-specific terms such as “plant biomass” or “row biomass” are more appropriate for biomass measured on spaced plant plots or row plots. These terms would clearly indicate that measurements on seeded plots where there is intensive interplant competition are not the same trait as those made on plants without competition. Keywords Panicum virgatum . Breeding . Genetics
Introduction Switchgrass (Panicum virgatum L.) is undergoing intensive development as a biomass crop to support the production of energy from perennial grasslands [32, 43]. Selection and breeding efforts have been initiated in at least 12 locations within North America, spanning at least seven plant hardiness zones and ranging from the Great Plains to the Atlantic Seaboard [10]. The methods and traits that have received focus from these breeding programs are as diverse as their geographic range. However, improvement of biomass yield is the
* Michael D. Casler [email protected]; [email protected] 1
USDA-ARS, U.S. Dairy Forage Research Center, 1925 Linden Dr, Madison, WI 53706-1108, USA
single unifying theme for all of these breeding programs, in an effort to make this
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