Dissection of Genotypic and Phenotypic Variation in Shrub Willow (Salix purpurea)

The recent completion of the shrub willow genome (Salix purpurea clone ID 94006) has provided an opportunity to expand the genomic resources that are available. Genetic studies can take advantage of a reference sequence to enhance the precision of trait mapping and subsequent integration through breeding efforts. S. purpurea is a core reference species for breeding shrub willow bioenergy crops in North America, and has been used in over 30% of all intra- and inter-specific hybrids produced within our breeding program. Due to the large presence of this species within many pedigrees, all of the 112 S. purpurea accessions within the germplasm collection at Cornell University were used to develop an association mapping panel. The population was genotyped using GBS and extensively phenotyped for several key growth and physiological traits, as well as physical and chemical wood properties across two years and three experimental sites. Association mapping has been used to identify candidate genes for high biomass yield and test for variation amongst traits relating to yield and composition and detect species-specific SNP alleles. Unfiltered data produced ~288K SNPs where filtering produced ~25K high quality SNPs used for analysis.  The genetic dissection of natural phenotypic variations in shrub willow will allow us to find the loci involved in these complex traits in supplement to ongoing QTL studies.