Alfalfa has been cultivated in many regions around the world as an important forage crop due to its nutritive value to livestock and ability to adapt to various environments. However, the genetic basis by which plasticity of quality-relevant traits influence alfalfa adaption to different water conditions remain largely unknown. In the present study, 198 accessions of alfalfa of the core collection for drought tolerance were evaluated for 26 forage quality traits in a field trial under an imposed deficit irrigation gradient. Regression analysis between quality traits and water stress revealed that values of fiber-related traits were negatively correlated with values of energy-related traits as water deficit increased. More than one hundred significant markers associated with forage quality under different water treatments were identified using genome-wide association studies with genotyping by sequencing. Among them, 131 markers associated with multiple traits in all the water deficit treatments. Most of the associated markers were dependent to the levels of water deficit, suggesting genetic controls for forage quality traits were dependent to the stress treatment. Twenty-four loci associated with forage quality were annotated to functional genes that may play roles in cell development or in response to water stress. This study addressed the genetic base of phenotypic variation of forage quality traits under water deficit. The SNP markers identified in this study will be useful in marker-assisted selection for the genetic improvement of alfalfa with enhanced drought tolerance while maintaining forage quality.

中文翻译：

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鉴定与四倍体苜蓿苜蓿（Medicago sativa L.）水分亏缺相关的饲草质量相关基因位点。

紫花苜蓿因其对牲畜的营养价值和适应各种环境的能力，已在世界许多地区作为重要的牧草作物被种植。但是，质量相关性状的可塑性影响苜蓿对不同水分条件的适应性的遗传基础仍是未知之数。在本研究中，在田间试验中，在强制灌溉不足的梯度下，对核心品种的198种紫花苜蓿的耐旱性进行了评估，以评估其26种草料的品质性状。品质性状与水分胁迫之间的回归分析表明，随着水分亏缺的增加，纤维相关性状的价值与能量相关性状的价值呈负相关。使用全基因组关联研究和测序进行基因分型，鉴定出一百种与不同水处理条件下的牧草品质相关的重要标记。在所有缺水处理中，有131个与多种性状相关的标记。大多数相关的标志物都依赖于水分缺乏水平，这表明饲草质量性状的遗传控制依赖于胁迫处理。与饲料质量相关的二十四个基因座被注释为功能基因，这些基因可能在细胞发育或响应水分胁迫中起作用。这项研究解决了缺水条件下饲草质量性状表型变异的遗传基础。