Assessment of Genotype Ranking in Long-term Biomass Production of Salix Based on Juvenile Plant Traits: Breeding Implications

Abstract

Willow (Salix spp.) is among the most promising energy crops to be grown on agricultural land and breeding research to increase biomass yield of this perennial crop is performed in Europe and North America. Biomass willows are grown in short rotation and harvests are performed every 3 to 5 years (i.e., at 3- to 5-year cutting cycles) for a period of up to 25 years. However, breeding programs to improve long-term biomass yield are often relying on the results of short-term screening studies performed on juvenile plants. A pre-requisite for successful breeding of perennial energy crops is thus the identification of relevant juvenile plant traits indicative of long-term plant performance under field conditions. In this study a number of juvenile plant traits, measured at various Salix genotypes grown in a short-term experiment were evaluated in terms of their capacity to predict the long-term performance in biomass production after the first and second cutting cycle. The objective was to develop a simple model linking juvenile plant traits such as shoot biomass, total leaf area and leaf nitrogen (N) concentration to the long-term biomass productivity of field-grown plants. A two-component regression model combining juvenile shoot biomass and leaf N concentration provided the highest prediction accuracy (coefficients of determination around 0.8). The model based on two easy-to-measure juvenile plant traits clearly has implications for willow breeding programs. The implications for breeding are discussed in the light of the possibilities and limitations associated with the chosen approach.

Appendix

Appendix Mean shoot biomass per stool (±SE; n = 4 variety plots) of six Salix varieties grown at two locations (Pustnäs and Ultuna) and four treatments in central Sweden after the second cutting cycle (2004–2006). Destructive shoot harvest was performed during the winter of 2006/2007 and according to methods described by [19]. W water, F fertilization, L low, H high. The mean air temperatures during the months May to September of 2004, 2005 and 2006 were 14.1°C, 14.3°C and 15.7°C, respectively, and the corresponding precipitation sums were 325 mm, 321 mm and 260 mm, respectively (data from the Ultuna climate station)