Genetic control of fiber properties and growth in triploid hybrid clones of Populus tomentosa

To better understand the genetic control of fiber properties (fiber length [FL], fiber width [FW] and coarseness [C]) and growth traits (tree height [H], diameter at breast height [DBH] and stem volume [SV]) in triploid hybrid clones of Populus tomentosa carr., genetic relationships among selected fiber properties with growth traits were examined in five-year-old clonal field trials located in Yanzhou, Gaotang and Xiangfen, China. In total, 180 trees from 10 clones were sampled from the three sites. The site had a moderate effect on FW, C and tree growth, and a highly significant (P<0.001) effect on FL and fiber length/width (FL/W). Clonal effects were also significant (P<0.05) for all studied traits except for the DBH and SV. Clone×site interactions were significant for all studied traits (except for FL). The estimated repeatability of clonal mean for FL (0.91) was higher than for FW (0.88), C (0.77), FL/W (0.74), H (0.62), DBH (0.61) and SV (0.55). Intersite genetic correlation estimates indicated that fiber properties were more stable than growth traits. Positively insignificant genetic correlation estimates between FL and growth trait and negatively insignificant genetic correlation estimates between C and growth traits were observed. This suggests that in the triploid hybrid poplar, clones selection for growth traits will not result in a significant increase or reduction in the fiber properties.