Nucleotide polymorphisms associated with climate and physiological traits in silver fir (Abies alba Mill.) provenances

Abstract

Single-nucleotide polymorphisms in seven candidate genes for drought and heat tolerance identified in earlier studies were studied in 13 populations of Abies alba Mill. covering the eastern and southeastern half of the distribution range. Trees were planted in a provenance trial plot of the international experiment IUFRO 2005 in Hertník, Slovakia. In parallel, genotyped trees were also scored for physiological traits (PSII thermotolerance, chlorophyll a fluorescence kinetics, partly gas exchange, assimilatory pigments, needle osmotic potential). For the detection of natural selection imprints, we used different methods: analysis of FST-outliers, testing of SNP–climate associations and SNP–phenotype associations. FST-outlier analysis revealed 2 SNPs with signals of selection. Moreover, three other SNPs showed significant association with latitude or bioclimatic variables; one of them (C/T polymorphism in a gene coding for serine/threonine phosphatase) was significantly associated with needle osmotic potential and marginally with other drought-related physiological traits. That may indicate its role in drought-stress response. In addition, T/C polymorphism in a gene coding for reduced epidermal fluorescence 4 was found to be involved in heat-stress response. However, migration history seems to be a more important driver of differentiation at SNPs in the studied candidate genes than recent adaptation.