Genotype-environment interaction and stability of fiber properties and growth traits in triploid hybrid clones of Populus tomentosa

Background Clones provide a sensitive method for evaluating genotypic stability and detecting genotype-environment (G × E) interactions because of non-additive genetic effects among clones and there being no genetic effect among ramets of an ortet. With this study, we aimed to confirm and expand earlier findings, estimate stability parameters, and provide accurate estimates of clonal repeatabilities and genetic gains for a triploid breeding program of P. tomentosa Carr. Results Six 5-year-old clonal trials established in Northern China were used to determine the clonal variation, clone × site interactions, and the stability parameters of fiber properties of wood and growth traits. 360 trees from ten hybrid clones were collected from six sites. The clonal and site effects had a highly significant effect (P < 0.001) for all studied traits. While the clone × site interactions had a highly significant effect (P < 0.001) on fiber length (FL), coarseness (C), and tree growth (tree height [H], diameter at breast height [DBH] and stem volume [SV]), and a moderate effect (P < 0.05) on fiber width (FW) and fiber length/width (FL/W). For FL and SV, most of the triploid hybrid clones had higher reaction norms to the improvement in growth conditions and higher phenotypic plasticity. The estimated clonal repeatability of FW (0.93) was slightly higher than for FL (0.89), FL/W (0.83), C (0.91), DBH (0.76), H (0.85), and SV (0.80). Three clonal testing sites were sufficient to estimate quantitative parameters of fiber properties, however, more clonal testing sites would help improve the accuracy of quantitative parameters of the growth traits. Conclusions Our results highlight that accurate estimation of quantitative parameters for growth traits in triploid hybrid clones of P. tomentosa requires more clonal testing sites than the fiber properties.

Genotype-Environment Interaction and Stability of Fiber Properties and Growth Traits in Triploid Hybrid Clones of Populus Tomentosa

Background: Clones provide a sensitive method for evaluating genotypic stability and detecting genotype-environment (G × E) interactions because of non-additive genetic effects among clones and no genetic effect among ramets of an ortet. The experiments aimed at confirming and expanding the earlier findings, estimating stability parameters, and providing accurate estimates of clonal repeatabilities and genetic gains for an triploid breeding programme of Populus tomentosa Carr. Results: Six 5-year-old clonal trials established in Northern China were used to determine the clonal variation, clone × site interactions and the stability parameters of fiber properties of wood and growth traits. Three hundred sixty trees from ten hybrid clones were collected in the six sites. The clonal and site effects had a highly significant effect (P < 0.001) for all studied traits. The clone × site interactions had a highly significant effect (P < 0.001) on fiber length (FL), coarseness (C), and tree growth (tree height [H], diameter at breast height [DBH] and stem volume [SV]), and a moderate effect (P < 0.05) on fiber width (FW) and fiber length/width (FL/W). For FL and SV, most of the triploid hybrid clones had higher reaction norms to the improvement in growth conditions and higher phenotypic plasticity. The estimated clonal repeatability of FW (0.93) was slightly higher than for FL (0.89), FL/W (0.83), C (0.91), DBH (0.76), H (0.85), and SV (0.80). Three clonal testing sites were sufficient to estimate quantitative parameters of fiber properties. However, more than three clonal testing sites will help improve the accuracy of quantitative parameters of growth traits.Conclusions: Our results unraveled that accurate estimation of quantitative parameters for growth traits in triploid hybrid clones of Populus tomentosa required more clonal testing sites than fiber properties.