Abstract
BackgroundThe American Beech tree (Fagus grandifolia Ehrh.), native to eastern North America, is ecologically important and provides high quality wood products. This species is susceptible to beech bark disease (BBD) and is facing high rates of mortality in North America. The disease occurs from an interaction between the woolly beech scale insect (Cryptococcus fagisuga), one of two species of the fungus Neonectria (N. faginata or N. ditissima), and American Beech trees.MethodsIn this case-control genome-wide association study (GWAS), we tested 16 K high quality SNPs using the Affymetrix Axiom 1.5 K – 50 K assay to genotype an association population of 514 individuals. We also conducted linkage analysis in a full-sib family of 115 individuals. Fisher’s exact test and logistic regression tests were performed to test associations between SNPs and phenotypes.ResultsAssociation tests revealed four highly significant SNPs on chromosome (Chr) 5 for a single gene (Mt), which encodes a mRNA for metallothionein-like protein (metal ion binding) in Fagus sylvatica. Metallothioneins represent Cys-rich metal chelators able to coordinate metal atoms and may play an important role in the resistance mechanisms against beech scale insect.ConclusionThe GWAS study has identified a single locus of major effect contributing to beech bark disease resistance. Knowledge of this genetic locus contributing to resistance might be used in applied breeding, conservation and restoration programs.
Highlights
The American Beech tree (Fagus grandifolia Ehrh.), native to eastern North America, is ecologically important and provides high quality wood products
Fagus sylvatica (European beech) mRNA for methallothionein-like protein, Metal ion binding. To our knowledge, this is the first study designed to determine the genetic factors of disease resistance to beech bark disease (BBD) with genome scan analysis in American beech tree
The results presented identified four highly significant markers associated with a single locus located on chromosome (Chr) 5
Summary
The American Beech tree (Fagus grandifolia Ehrh.), native to eastern North America, is ecologically important and provides high quality wood products. This species is susceptible to beech bark disease (BBD) and is facing high rates of mortality in North America. The number of chromosomes is generally stable within the Fagaceae family (2n = 24), with occasional changes (2n = 24 + 1, 2, 3) resulting from irregular segregation at mitosis [4] Both Fagus grandifolia and F. sylvatica have the most rudimentary genomes within the family, making their genomes attractive for comparative genomics studies [3]
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