Switchgrass (Panicum virgatum L.) breeders use spaced-seedling plots for evaluations of biomass yield, but prior studies are ambiguous about the relationship between performance in spaced plots and commercial seeded sward performance. This study used a split-plot incomplete block design to evaluate 52 half-sib switchgrass families across two years to determine the correlations among four different plot types (including seeded swards) and four individual plant traits. Plots (1.62 m²) that contained 3, 6, and 18 plants had mean yields of 5.92, 8.04, and 11.06 Mg ha^–1, respectively, while seeded-sward plots had a mean of 5.37 Mg ha^–1. In a mixed-model analysis including family-, year-, and plot-type interactions with a spatial-spline correction, the largest proportion of family variance was accounted for by the main family effect (48%), while the plot type-by-family effect was only 17% of family variance. These results indicate that spaced-plant plots are reasonable surrogates for biomass performance in sward conditions. Yield reliability was 0.50 across all plot types with a mean of 0.46 for individual plot types. Surrogates for sward yield varied due to genetic background of the families. Yield of families derived from the Liberty cultivar (n = 32) had genetic correlations with winter survivorship scores (0.66). Diverse lowland ecotype families (n = 20) had genetic correlations with plant height and heading date. This study highlighted a major difference in performance among the plot types, specifically that seeded swards have depressed yield due to high plant density. This should encourage further research for the mechanism behind this difference in performance.

中文翻译：

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草地条件下柳枝稷性能与替代措施之间的遗传相关性

柳枝稷 ( Panicum virgatum L.) 育种者使用间隔苗圃来评估生物量产量，但先前的研究对于间隔地块的性能与商业播种草坪性能之间的关系并不明确。本研究使用裂区不完全区组设计在两年内评估 52 个半同胞柳枝稷科，以确定四种不同地块类型（包括播种区）和四种个体植物性状之间的相关性。包含 3、6 和 18 株植物的地块 (1.62 m ^{2 ) 的平均产量分别为 5.92、8.04 和 11.06 Mg ha -1}，而播种地块的平均产量为 5.37 Mg ha ^-1. 在包括家庭、年份和地块类型交互以及空间样条校正的混合模型分析中，家庭方差的最大比例由主要家庭效应（48%）解释，而地块类型由- 家庭效应仅为家庭方差的 17%。这些结果表明，间隔植物地块是草地条件下生物量性能的合理替代物。所有地块类型的产量可靠性为 0.50，单个地块类型的平均值为 0.46。草地产量的替代品因家庭的遗传背景而异。来自 Liberty 品种的家庭产量 ( n  = 32) 与冬季生存评分 (0.66) 具有遗传相关性。多样的低地生态型家庭（n = 20) 与株高和抽穗期有遗传相关性。这项研究强调了地块类型之间性能的主要差异，特别是播种的草地由于植物密度高而降低了产量。这应该鼓励进一步研究这种性能差异背后的机制。