A candidate gene-based association study reveals SNPs significantly associated with bud burst in European beech (Fagus sylvatica L.)

European beech (Fagus sylvatica L.) is one of the most important deciduous forest tree species in Central Europe. Nevertheless, its adaptation potential to climate change is controversially discussed, and little is known about the molecular basis of climate change-relevant traits like bud burst. Here, we directly observed bud burst of beech seedlings originating from six different populations in Northern Germany in a large translocation experiment comprising 3600 individuals in three consecutive years. We genotyped more than 1200 individuals from the translocation experiment using 46 different SNP markers previously identified in candidate genes for bud burst. Association and outlier analyses were conducted to identify potentially adaptive SNPs. We found 10 SNPs significantly associated with bud burst in at least one analyzed year and five outlier SNPs potentially under directional selection. One SNP located in a histone gene was simultaneously revealed by both association and outlier analyses. This SNP might have the highest probability of being involved in the expression of bud burst.