Section of Evolution and Ecology, University of California, Davis, 95616, USA.
Genetics. 2009 Aug;182(4):1289-302. doi: 10.1534/genetics.109.102350. Epub 2009 Jun 1.
Adaptation to cold is one of the greatest challenges to forest trees. This process is highly synchronized with environmental cues relating to photoperiod and temperature. Here, we use a candidate gene-based approach to search for genetic associations between 384 single-nucleotide polymorphism (SNP) markers from 117 candidate genes and 21 cold-hardiness related traits. A general linear model approach, including population structure estimates as covariates, was implemented for each marker-trait pair. We discovered 30 highly significant genetic associations [false discovery rate (FDR) Q < 0.10] across 12 candidate genes and 10 of the 21 traits. We also detected a set of 7 markers that had elevated levels of differentiation between sampling sites situated across the Cascade crest in northeastern Washington. Marker effects were small (r(2) < 0.05) and within the range of those published previously for forest trees. The derived SNP allele, as measured by a comparison to a recently diverged sister species, typically affected the phenotype in a way consistent with cold hardiness. The majority of markers were characterized as having largely nonadditive modes of gene action, especially underdominance in the case of cold-tolerance related phenotypes. We place these results in the context of trade-offs between the abilities to grow longer and to avoid fall cold damage, as well as putative epigenetic effects. These associations provide insight into the genetic components of complex traits in coastal Douglas fir, as well as highlight the need for landscape genetic approaches to the detection of adaptive genetic diversity.
适应寒冷是森林树木面临的最大挑战之一。这个过程与光周期和温度有关的环境线索高度同步。在这里，我们使用基于候选基因的方法，在 117 个候选基因中的 384 个单核苷酸多态性 (SNP) 标记与 21 个抗寒性相关性状之间搜索遗传关联。我们为每个标记-性状对实施了包含群体结构估计作为协变量的一般线性模型方法。我们在 12 个候选基因和 10 个 21 个性状中的 30 个高度显著的遗传关联[错误发现率 (FDR) Q < 0.10]。我们还在华盛顿东北部卡斯卡德山脊沿线的采样点之间检测到一组 7 个标记，这些标记之间存在高水平的分化。标记效应很小 (r(2) < 0.05)，处于先前发表的森林树木范围内。与最近分化的姐妹种相比，所测的 SNP 等位基因通常以与耐寒性一致的方式影响表型。大多数标记的基因作用模式主要是非加性的，尤其是在与耐寒性相关的表型情况下为下位性。我们将这些结果置于在生长时间更长和避免秋季寒冷损害之间的权衡，以及潜在的表观遗传效应的背景下。这些关联提供了对沿海道格拉斯冷杉复杂性状遗传成分的深入了解，并突出了需要采用景观遗传方法来检测适应性遗传多样性。
