Shadetolerance is an important factor for cultivar selection in urban areas. Diploid (2n = 2x = 18) cultivars of St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] with moderate to high shade tolerance have been popular choices for residential and commercial landscapes in the southern United States. This study evaluated 26 elite drought resistant diploid and interploid (polyploid × diploid) hybrids and four commercial cultivars under 75% continuous shade from 20 June 2017 through 30 Oct. 2018. Biweekly data were collected during the growing season for percent green cover, visual turfgrass quality, canopy color, shoot density, and daily leaf elongation rates (DER; mm d^–1). Spring greenup was rated annually, and to gray leaf spot incidence was rated when naturally occurring. All genotypes lost green cover through 2017, and greenup was delayed transitioning into the summer of 2018 when most diploids struggled to recover from disease, shade, and winter injury whereas, on an average, interploid hybrids reached up to 84.0% green cover. Daily leaf elongation rates were lower for diploids than polyploids in both years. Turfgrass quality, color, and density generally declined under shade as expected. Overall, three interploid hybrids (DALSA 1329, 1404, and 1406) were the top performers demonstrating good retention of turfgrass performance traits and reduced DER under shade.

中文翻译：

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中等遮荫下圣奥古斯丁草二倍体和间倍体杂种的性能

耐荫性是城市地区品种选择的重要因素。具有中等至高耐荫性 的圣奥古斯丁草[ Stenotaphrum secundatum (Walt.) Kuntze] 的二倍体 (2 n  = 2 x = 18) 品种一直是美国南部住宅和商业景观的热门选择。本研究评估了 2017 年 6 月 20 日至 2018 年 10 月 30 日在 75% 连续遮荫下的 26 个优良抗旱二倍体和间倍体（多倍体 × 二倍体）杂种和四个商业栽培品种。在生长季节收集了每两周一次的绿色覆盖率、视觉草坪草的数据质量、冠层颜色、枝条密度和每日叶片伸长率（DER；mm d ^–1）。每年评估春季绿化，并在自然发生时评估灰斑病发生率。到 2017 年，所有基因型都失去了绿化覆盖，绿化被推迟到 2018 年夏季，当时大多数二倍体都在努力从疾病、阴影和冬季伤害中恢复过来，而平均而言，间倍体杂种的绿化覆盖率高达 84.0%。在这两年中，二倍体的每日叶片伸长率低于多倍体。正如预期的那样，在阴凉处草坪草的质量、颜色和密度普遍下降。总体而言，三个间倍体杂种（DALSA 1329、1404 和 1406）表现最佳，表现出良好的草坪性能特征保留和减少的遮荫下 DER。