| Genetic improvement of fast-growing shrub willow (Salix spp.), a proven perennial bioenergy crop for temperate climates, will require methods for rapid determination of biomass composition and will be expedited by a thorough understanding of the molecular basis for cell wall composition. High resolution thermogravimetric analysis (HR-TGA) is a reliable technique to identify differences in stem biomass composition among shrub willow varieties produced through breeding and has been developed for rapid, low-cost trait phenotyping and selection of shrub willow genotypes with optimized biomass composition. To validate the HR-TGA method, a selection of 25 shrub willow varieties was analyzed using traditional wet chemistry techniques and the results were compared by regression analysis to the results of HR-TGA. Correlations of the percent hemicellulose, cellulose, and lignin were all significant with R2 values over 0.7. Furthermore, the HR-TGA method was able to identify compositional differences among various age classes of willow and biomass samples with and without bark. The molecular basis for differences in biomass composition is being investigated by studying the expression of genes encoding enzymes involved in lignin biosynthesis and selected carbohydrate active enzymes (CAZymes). Fragments of nearly 20 genes have been cloned from willow cDNA and their expression patterns associated with stem growth throughout the growing season were analyzed by probe-based, real-time qPCR. Correlating patterns of gene expression with variation in biomass composition among selected shrub willow varieties and siblings within a hybrid family will provide insights into the genetic regulation of lignocellulosic deposition in this important bioenergy crop.;Key Words: bioenergy, biofuels, cell wall biosynthesis, cellulose, hemicelluloses, lignin, thermogravimetric analysis... |
