Exome resequencing and GWAS for growth, ecophysiology, and chemical and metabolomic composition of wood of Populus trichocarpa

Abstract

Background: Populus trichocarpa is an important forest tree species for the generation of lignocellulosic ethanol. Understanding the genomic basis of biomass production and chemical composition of wood is fundamental in supporting genetic improvement programs. Considerable variation has been observed in this species for complex traits related to growth, phenology, ecophysiology and wood chemistry. Those traits are influenced by both polygenic control and environmental effects, and their genome architecture and regulation are only partially understood. Genome wide association studies (GWAS) represent an approach to advance that aim using thousands of single nucleotide polymorphisms (SNPs). Genotyping using exome capture methodologies represent an efficient approach to perform GWAS. Results: A GWAS using 461 P. trichocarpa clones, representing 101 provenances collected from Oregon and Washington, and 813K single nucleotide polymorphisms (SNPs), identified a variable number of significant SNPs in association with the assessed traits. Associated single-markers (q< 0.1) ranged from 3 to 110 per trait. The SNPs had a cumulative effect of up to 40.6% of the phenotypic variation of any given trait. Similarly, multiple-marker analyses detected between 16 and 291 significant windows for the phenotypes. The SNPs resided within genes that encode proteins belonging to different functional classes as well as in intergenic regions. Conclusion: SNP-markers within and proximal to genes associated with traits of importance for biomass production were detected. They contribute to characterize the genomic architecture of P. trichocarpa biomass required to support the development and application of marker breeding technologies.