Genotypic Variation In Wood Properties Of Triploid Hybrid Varieties Of White Poplar

Triploid hybrid varieties of white poplar are combined with both hybrid and polyploidy vigors. Compared to P. tomentosa, the triploid hybrid varieties have a high growth rate, longer fibers, and lower lignin content. It was widely planted in northern China to obtain a high fiber yield from crops. In order to a clear understanding of the genetic variations of wood properties, giving a prerequisite for breeding and utilizing in triploid hybrid varieties of white poplar, the genetic variations of wood properties, variability in wood properties along the stem as well as between different initial spacing were estimated based on five sites clonal trails and a spacing trail. Major results as follows,1. Significant genotypic, environment and genotypic x environment interaction were detected for basic wood density, fiber traits and lignin contant of triploid hybrid varieties of white poplar. The phenotypic variances of basic wood and fiber traits were mainly composed by genotypic effect, secondly by environment effect. The genotypic, environment and genotypic x environment interaction effects have similar contribution for lignin phenotypic variances. However, the contribution of environment effect was much higher than the other two effects in phenotypic variances of alcohol-benzene extractives.2. The genetic parameters of wood properties were estimated. The results suggested that the most wood properties of triploid hybrid varieties of white poplar were under the moderate to high genetic controlled. The repeatability of basic wood density and fiber traits ranged from0.62-0.95. Significant differences of triploid hybrid varieties were found on lignin, excluding in Gaotang site, and the repeatability ranged from0.78～0.89. However, the significant differences of triploid hybrid varieties were only detected in Gaotang and Zhengzhou sites, and the repeatability ranged from0.71～0.93. These indicated that the lignin should be the primary consideration in wood chemical composition traits under the clonal selecting program. In addition, moderate to strong and significant positive genotypic correlations between basic wood density and fiber traits were found in five trails, however it was no consistency variations for the genotypic correlations between wood chemical composition traits and the other wood properties among individual site.3. Clone selection for pulp wood was explored by principal component analysis method with all studied traits combine based on genetic parameters. The studies suggested that the varieties of B305and B331at Gaotang site, B304and B331at Yanzhou site, B304and B306at Xiangfen site, B305and B333at Taiyuan site, as well as B304and B306at Zhengzhou site were suitable for pulp industry, according to a higher basic wood density and holocellulose, favourable fiber traits, as well as a lower lignin and alcohol-benzene extractives.4. The type B genetic correlations between different sites were evaluated for wood properties of triploid hybrid varieties of white poplar. The researches indicated that the basic wood density and fiber traits were rather stable across environments than the wood chemical composition traits. Positive and significant type B genetic correlations were found on basic wood density and fiber traits between individual sites. However, the phenotype variations of lignin and alcohol-benzene extractives between Taiyuan site and the other sites were mainly came from the effect of genotypic x environment interaction.5. The effects of sampled heights on wood basic density and fiber traits were determined. Significant height position effect for fiber length and coarseness were detected, with it composed36.63%and3.77%for phenotype variations, respectively. The results based on analysis of variance indicated that it was effective to estimate the genetic parameters of wood properties with the same simple height. Moreover, the basic wood density and fiber traits were influenced by environment during the growth of triploid hybrid varieties of white poplar.6. The effects of planting spacing on wood density and fiber traits were determined. With the lowing planted spacing, the basic wood density was initially increased then decreased. However, the fiber length increased with lowing planting spacing, whereas the fiber width and coarseness appeared fluctuated trends. In addition, the correlations between these wood properties varied with the lowing planting spacing. The research suggested that there were no significant effects of planting spacing and genotypic x spacing on basic wood density and fiber traits. These indicated that it was more effectively to improved the growth traits rather than the wood properties of triploid hybrid varieties of white poplar under the planting spacing studied in this research.