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Keywords:

  • association mapping;
  • budset;
  • clinal variation;
  • cold hardiness;
  • single nucleotide polymorphism;
  • Sitka spruce (Picea sitchensis)

Summary

  • Genecological studies in widespread tree species have revealed steep genetic clines along environmental gradients for climate-related traits. In a changing climate, the ecological and economic importance of conifers necessitates an appraisal of how molecular genetic variation shapes quantitative trait variation, and one of the most promising approaches to answer this question is association mapping.
  • We phenotyped a wide collection of 410 individuals of the widely distributed conifer Sitka spruce rangewide (Picea sitchensis) for budset timing and autumn cold hardiness, and genotyped these individuals for a panel of 768 single nucleotide polymorphisms (SNPs) representing > 200 expressed nuclear genes.
  • After correcting for population structure, associations were detected in 28 of the candidate genes, which cumulatively explained 28 and 34% of the phenotypic variance in cold hardiness and budset, respectively. Most notable among the associations were five genes putatively involved in light signal transduction, the key pathway regulating autumn growth cessation in perennials. Many SNPs with phenotypic associations were also correlated with at least one climate variable.
  • This study represents a significant step toward the goal of characterizing the genomic basis of adaptation to local climate in conifers, and provides an important resource for breeding and conservation genetics in a changing climate.