Morphological and physiological traits influencing biomass productivity in short-rotation coppice poplar

Fast-growing hybrid poplar (Populus spp.) have potential as a short-rotation coppice crop grown for biomass energy. This work identifies traits for fast growth studied in an American interspecific pedigree derived from Populus trichocarpa Torr. & A. Gray x Populus deltoides Marsh. grown in the United Kingdom for the first time. The biomass yield after the first coppice rotation was estimated to range from 0.04 to 23.68 oven-dried t.ha(-1.)year(-1). This great range suggests that genotypes from this pedigree may be used to understand the genetic basis of high yield in short-rotation coppice, which would be advantageous for informing breeding programs for biomass crops. Relationships between stem, leaf, cell traits, and biomass yield were investigated. Partial least-squares analysis was used to order the traits by importance. The traits most influential on biomass were maximum stem height throughout the growing season, basal diameter, number of stems, and number of sylleptic branches, which showed high heritability, indicating excellent potential for breeding programs. The leaf traits, leaf area, number of leaves on the leading stem, and plastochron index were also associated with an increase in biomass, leading to a better understanding of this trait.