Many agricultural lands in the western United States consist of soil with high concentrations of salt, which is detrimental to alfalfa (Medicago sativa L.) growth and production, especially in the region where water resource is limited. Developing alfalfa varieties with salt tolerance is imperative for sustainable production under increasing soil salinity. In the present study, we used advanced alfalfa breeding populations and evaluated five traits related to salt tolerance including biomass dry weight (DW) and fresh weight (FW), plant height (PH), leaf relative water content (RWC), and stomatal conductance (SC) under control and salt stress. Stress susceptibility index (SSI) of each trait and single‐nucleotide polymorphism (SNP) markers generated by genotyping‐by‐sequencing (GBS) were used for genome‐wide association studies (GWAS) to identify loci associated with salt tolerance. A total of 53 significant SNPs associated with salt tolerance were identified and they were located at 49 loci through eight chromosomes. A Basic Local Alignment Search Tool (BLAST) search of the regions surrounding the SNPs revealed 21 putative candidate genes associated with salt tolerance. The genetic architecture for traits related to salt tolerance characterized in this report could help in understanding the genetic mechanism by which salt stress affects plant growth and production in alfalfa. The markers and candidate genes identified in the present study would be useful for marker‐assisted selection (MAS) in breeding salt‐tolerant alfalfa after validation of the markers.

中文翻译：

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使用全基因组关联研究在四倍体苜蓿的先进育种种群中与耐盐性相关的遗传基因座。

美国西部的许多农业用地都含有高盐分的土壤，这对苜蓿（Medicago sativaL.）的增长和生产，特别是在水资源有限的地区。在土壤盐分增加的情况下，开发具有耐盐性的苜蓿品种对于可持续生产势在必行。在本研究中，我们使用了苜蓿的先进育种种群，并评估了与耐盐性相关的五个性状，包括生物量干重（DW）和鲜重（FW），株高（PH），叶片相对含水量（RWC）和气孔导度（SC）受控制和盐胁迫。每个性状的胁迫敏感性指数（SSI）和通过基因分型测序（GBS）生成的单核苷酸多态性（SNP）标记用于全基因组关联研究（GWAS），以鉴定与耐盐性相关的基因座。总共鉴定出53个与耐盐性相关的SNP，它们位于8个染色体的49个基因座上。一个基本的局部比对搜索工具（BLAST）搜索围绕SNPs的区域揭示了21个与耐盐性相关的推定候选基因。本报告中描述的与耐盐性相关的性状的遗传结构可以帮助理解盐胁迫影响苜蓿植物生长和生产的遗传机制。在本研究中鉴定出的标记和候选基因将在验证标记后用于育种耐盐苜蓿的标记辅助选择（MAS）。一个基本的局部比对搜索工具（BLAST）搜索围绕SNPs的区域揭示了21个与耐盐性相关的推定候选基因。本报告中描述的与耐盐性相关的性状的遗传结构可以帮助理解盐胁迫影响苜蓿植物生长和生产的遗传机制。在本研究中鉴定出的标记和候选基因将在验证标记后用于育种耐盐苜蓿的标记辅助选择（MAS）。一个基本的局部比对搜索工具（BLAST）搜索围绕SNPs的区域揭示了21个与耐盐性相关的推定候选基因。本报告中描述的与耐盐性相关的性状的遗传结构可以帮助理解盐胁迫影响苜蓿植物生长和生产的遗传机制。在本研究中鉴定出的标记和候选基因将在验证标记后用于育种耐盐苜蓿的标记辅助选择（MAS）。