Abstract
Through the use of genome-wide association studies (GWAS) mapping it is possible to establish the genetic basis of phenotypic trait variation. Our GWAS study presents the first such effort in Norway spruce (Picea abies (L). Karst.) for the traits related to wood tracheid characteristics. The study employed an exome capture genotyping approach that generated 178 101 Single Nucleotide Polymorphisms (SNPs) from 40 018 probes within a population of 517 Norway spruce mother trees. We applied a least absolute shrinkage and selection operator (LASSO) based association mapping method using a functional multi-locus mapping approach, with a stability selection probability method as the hypothesis testing approach to determine significant Quantitative Trait Loci (QTLs). The analysis has provided 30 significant associations, the majority of which show specific expression in wood-forming tissues or high ubiquitous expression, potentially controlling tracheids dimensions, their cell wall thickness and microfibril angle. Among the most promising candidates based on our results and prior information for other species are: Picea abies BIG GRAIN 2 (PabBG2) with a predicted function in auxin transport and sensitivity, and MA_373300g0010 encoding a protein similar to wall-associated receptor kinases, which were both associated with cell wall thickness. The results demonstrate feasibility of GWAS to identify novel candidate genes controlling industrially-relevant tracheid traits in Norway spruce.
Highlights
Through the use of genome-wide association studies (GWAS) mapping it is possible to establish the genetic basis of phenotypic trait variation
The adapted central peak curves combined with the threshold at 20° resulted in an average of five years for MFATA, defining the inner core of lower quality timber with AM performed for the latent traits of M FACORE and MFAOUTER
These associations have identified a set of genes that could be exploited to alter wood tracheid traits for improving solid wood properties for its use in industrial processes
Summary
Through the use of genome-wide association studies (GWAS) mapping it is possible to establish the genetic basis of phenotypic trait variation. Similar models for the influence of cambial age and ring width have been presented for tracheid length, width and wall thickness models of Norway spruce, Sitka spruce, Scots pine and loblolly p ine[7]. Such results have indicated that changes in growth conditions over time acting mainly through crown development, will have an influence on wood structure development in Norway spruce[6]. These reports paid very little regard to the underlaying genetic factors influencing these phenotypes. When confounding factors are taken into consideration, LD mapping provides greater resolution than pedigree studies, since it utilizes markers in strong LD with putative causative genomic regions[17]
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