It has been shown that high resolution thermogravimetric analysis (HR-TGA) is a reliable technique to identify differences in stem biomass composition among shrub willow (Salix spp.) varieties selected in the breeding program at the State University of New York College of Environmental Science and Forestry (SUNY-ESF).  Rapid determination of biomass composition is critical to the breeding and selection of shrub willow varieties with optimized properties for downstream conversion.  In order to improve the process for identifying and selecting shrub willow varieties with distinct biomass compositions, HR-TGA was developed as a rapid, low-cost method for analyzing and screening unique willow genotypes.   For validation of the HR-TGA method through regression analysis, a set of 25 shrub willow varieties, characterized for growth features including yield, height, stem diameter, and disease and pest resistance, were analyzed using traditional wet chemistry techniques in addition to HR-TGA.  The molecular basis of differences in biomass composition is also being investigated to provide molecular tools that will further improve the shrub willow breeding program.  Genes encoding enzymes involved in lignin biosynthesis and selected carbohydrate active enzymes (CAZys) are being cloned from willow and their expression patterns are being analyzed.  The long-term goal is to develop molecular markers for the early selection of genotypes with improved biomass properties.  Correlating patterns of gene expression with wood composition among selected shrub willow varieties and siblings within a hybrid family is a critical step in this process.