Genotypic parameters of wood density and fiber traits in triploid hybrid clones of Populus tomentosa at five clonal trials

A clear understanding of the genetic control of wood properties is a prerequisite for breeding for higher wood quality in Populus tomentosa Carr. hybrid clones. The experiments aimed at unraveling genetic and environmental effects on wood properties among triploid hybrid clones of P. tomentosa. We used 5-year-old clonal trials established in Northern China to assess the heritability of wood density and fiber traits. Two hundred seventy trees from nine clones were sampled in five sites. Site had a very significant effect on all recorded traits. Despite this large site effect, a tight genetic control was detected and clonal repeatability varied between 0.53 and 0.95. Significant genotype x environment interactions were detected for most of the traits. Moderate to tight correlation were evidenced among traits but they were not consistent with that in several cases that were site-dependent. Our results revealed a tight genetic control over several wood properties and therefore breeding programs might be able to improve wood density, fiber length, and coarseness in these hybrids.