Walnut production is challenged by climate change and abiotic stresses. Elucidating the genomic basis of adaptation to climate is essential to breeding drought-tolerant cultivars for enhanced productivity in arid and semi-arid regions. Here, we aimed to identify loci potentially involved in water use efficiency (WUE) and adaptation to drought in Persian walnut using a diverse panel of 95 walnut families (950 seedlings) from Iran, which show contrasting levels of water availability in their native habitats. We analyzed associations between phenotypic, genotypic, and environmental variables from data sets of 609 000 high-quality single nucleotide polymorphisms (SNPs), three categories of phenotypic traits [WUE-related traits under drought, their drought stress index, and principal components (PCs)], and 21 climate variables and their combination (first three PCs). Our genotype-phenotype analysis identified 22 significant and 266 suggestive associations, some of which were for multiple traits, suggesting their correlation and a possible common genetic control. Also, genotype-environment association analysis found 115 significant and 265 suggestive SNP loci that displayed potential signals of local adaptation. Several sets of stress-responsive genes were found in the genomic regions significantly associated with the aforementioned traits. Most of the candidate genes identified are involved in abscisic acid signaling, stomatal regulation, transduction of environmental signals, antioxidant defense system, osmotic adjustment, and leaf growth and development. Upon validation, the marker-trait associations identified for drought tolerance-related traits would allow the selection and development of new walnut rootstocks or scion cultivars with superior WUE.

中文翻译：

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结合表型，基因型和环境，揭示波斯核桃水分利用效率的遗传成分。

核桃生产受到气候变化和非生物胁迫的挑战。阐明适应气候变化的基因组基础对于在干旱和半干旱地区育种耐旱品种以提高生产力至关重要。在这里，我们旨在通过使用来自伊朗的95个核桃家族（950棵幼苗）的不同小组，来识别波斯核桃中可能与水分利用效率（WUE）和干旱适应相关的位点，这显示了其本地栖息地的可用水水平存在差异。我们分析了表型，基因型和环境变量之间的关联，这些数据来自609000个高质量单核苷酸多态性（SNP）数据集，三类表型性状[干旱下WUE相关性状，其干旱胁迫指数和主成分（PCs） ）]，和21个气候变量及其组合（前三台PC）。我们的基因型-表型分析确定了22个显着关联和266个暗示关联，其中一些与多种性状有关，表明它们之间的相关性和可能的​​共同遗传控制。此外，基因型与环境的关联分析发现115个显着的SNP位点和265个暗示性的SNP位点，显示了局部适应的潜在信号。在与上述性状显着相关的基因组区域中发现了几组应激反应基因。鉴定出的大多数候选基因都涉及脱落酸信号，气孔调节，环境信号转导，抗氧化剂防御系统，渗透调节以及叶片生长和发育。验证后，