Genotypic Variations of Biomass Feedstock Properties for Energy in Triploid Hybrid Clones of Populus tomentosa

Woody biomass feedstock produced from hybrid poplar can be converted into bioenergy via thermochemical and biochemical processes. To better understand the genetic control of key properties (biomass production, extractives, holocellulose, lignin, and higher heating value) that relate to the quality of biomass feedstock in triploid hybrid clones of Populus tomentosa, genetic relationships among selected traits were examined in 5-year-old clonal field trials located in Yanzhou, Gaotang, Xiangfen, Zhengzhou, and Taiyuan, northern China. In total, 270 trees from nine clones were sampled from the five sites. Site had a highly significant (P < 0.001) effect on biomass production, extractives, lignin, and higher heating value, and it had a moderate effect on holocellulose. Clonal effects were also significant (P < 0.05) for all studied traits except for holocellulose. Clone × site interactions were significant for all studied traits except for holocellulose. The estimated repeatability of clonal means for biomass production (0.81) was higher than for lignin (0.75), extractives (0.68), higher heating value (0.58), and holocellulose (0.54). A negative or significantly negative correlation between holocellulose, extractives, lignin, and higher heating value was observed at each site. This suggests that selection for holocellulose might lead to a reduction in extractives, lignin, and higher heating value in triploid breeding of P. tomentosa.