As boreal forests face significant threats from climate change, understanding evolutionary trajectories of coniferous species has become fundamental to adapting management and conservation to a drying climate. We examined the genomic architecture underlying adaptive variation related to drought tolerance in 43 populations of a widespread boreal conifer, white spruce (Picea glauca [Moench] Voss), by combining genotype–environment associations, genotype–phenotype associations, and transcriptomics. Adaptive genetic variation was identified by correlating allele frequencies for 6,153 single nucleotide polymorphisms from 2,606 candidate genes with temperature, precipitation and aridity gradients, and testing for significant associations between genotypes and 11 dendrometric and drought-related traits (i.e., anatomical, growth response and climate-sensitivity traits) using a polygenic model. We identified a set of 285 genes significantly associated with a climatic factor or a phenotypic trait, including 110 that were differentially expressed in response to drought under greenhouse-controlled conditions. The interlinked phenotype–genotype–environment network revealed eight high-confidence genes involved in white spruce adaptation to drought, of which four were drought-responsive in the expression analysis. Our findings represent a significant step toward the characterization of the genomic basis of drought tolerance and adaptation to climate in conifers, which is essential to enable the establishment of resilient forests in view of new climate conditions.

中文翻译：

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连接年轮表型、遗传关联和转录组学以破译广泛针叶树干旱适应的基因组结构

由于北方森林面临气候变化的重大威胁，了解针叶树物种的进化轨迹已成为使管理和保护适应干燥气候的基础。我们研究了 43 个广泛分布的北方针叶树、白云杉（Picea glauca ）种群中与耐旱性相关的适应性变异的基因组结构[Moench] Voss），通过结合基因型-环境关联、基因型-表型关联和转录组学。通过将 2,606 个候选基因的 6,153 个单核苷酸多态性的等位基因频率与温度、降水和干旱梯度相关联，并测试基因型与 11 个树状和干旱相关性状（即解剖学、生长反应和气候）之间的显着关联，确定了适应性遗传变异-敏感性特征）使用多基因模型。我们确定了一组 285 个与气候因素或表型性状显着相关的基因，其中 110 个在温室控制条件下响应干旱而差异表达。相互关联的表型-基因型-环境网络揭示了八个参与白云杉对干旱适应的高置信度基因，其中四个在表达分析中具有干旱响应性。我们的发现代表了针叶树耐旱性和适应气候的基因组基础特征的重要一步，这对于在新的气候条件下建立具有弹性的森林至关重要。