Contributions of environment and genotype to variation in shrub willow biomass composition

•Environment tends to exert stronger influence than genotype, but not for all traits.•Significant variation in composition is present among species and interspecific hybrids.•Cellulose content is strongly, negatively correlated with ash and lignin content.•Yield is negatively correlated with lignin and positively correlated with cellulose.•Cultivar selection based on yield results in greater cellulose produced per unit area. Yield improvement of woody bioenergy crops has been the major focus of breeding programs, but biomass quality is also important for conversion to biofuels. Using high-resolution thermogravimetric analysis, the composition of biomass samples from two shrub willow (Salix spp.) yield trial networks representing two distinct datasets were examined. Dataset 1 consisted of 12 yield trials containing 10 genotypes that mainly represented early cultivars from the US breeding program. Dataset 2 consisted of five trial locations containing 19 genotypes from later breeding efforts. Variation in ash and hemicellulose content were largely controlled by genetic factors, while cellulose and lignin content were heavily influenced by environmental effects. Mean biomass composition traits for dataset 1 were 2.1% ash, 42.4% cellulose, 18.7% hemicellulose and 25.5% lignin. For dataset 2 mean traits were 1.9% ash, 43.2% cellulose, 17.7% hemicellulose and 25.7% lignin. Yield was negatively correlated with lignin content and positively correlated with cellulose content at the level of environment. Elite triploid hybrid cultivars have the potential to produce more cellulose per unit area because of higher yields and/or greater cellulose content. These findings suggest that selection of genotypes for improved yield, as well as selection of growing environment, can improve feedstock quality for biofuel production.