Abstract
In order to determine suitable traits for selecting high-wood-yield Korean pine materials, eleven morphological characteristics (tree height, basal diameter, diameter at breast height, diameter at 3 meter height, stem straightness degree, crown breadth, crown height, branch angle, branch number per node, bark thickness, and stem volume) were investigated in a 38-year-old Korean pine clonal trial at Naozhi orchard. A statistical approach combining variance and regression analysis was used to extract appropriate traits for selecting elite clones. Results of variance analysis showed significant difference in variance sources in most of the traits, except for the stem straightness degree, which had a p-value of 0.94. Moderate to high coefficients of variation and clonal repeatability ranged from 10.73% to 35.45% and from 0.06% to 0.78%, respectively. Strong significant correlations on the phenotypic and genotypic levels were observed between the straightness traits and tree volume, but crown breadth was weakly correlated to the volume. Four principal components retaining up to 80% of the total variation were extracted, and stem volume, basal diameter, diameter at breast height, diameter at 3 meter height, tree height, and crown height displayed high correlation to these components (r ranged from 0.76 to 0.98). Based on the Type III sum of squares, tree height, diameter at breast height, and branch number showed significant information to explain the clonal variability based on stem volume. Using the extracted characteristics as the selection index, six clones (PK105, PK59, PK104, PK36, PK28, and K101) displayed the highest Qi values, with a selection rate of 5% corresponding to the genetic gain of 42.96% in stem volume. This study provides beneficial information for the selection of multiple traits for genetically improved genotypes of Korean pine.
Highlights
The Korean pine breeding program remains among the largest coniferous tree improvement programs in Northeastern China that are carried out [1]
Significant differences were found in all the investigated traits, providing a selection basis for breeding purposes (Table 1)
ANOVA results showed that the clonal phenotypic average values were significantly different in most of the traits (p ≤ 0.001), except for straightness degree (SSD), for which clone averages did not differ significantly (p = 0.94)
Summary
The Korean pine breeding program remains among the largest coniferous tree improvement programs in Northeastern China that are carried out [1]. Pinus koraiensis was primarily selected to increase its wood yield. A few years later, seed yield was taken into account, responding to users’ demand for the seeds and nuts of Korean pine and following the official decree in 2016 against the cutting of natural forests. P. koraiensis is much desired, being preferred in community reforestation projects following the services it provided in Northeastern China [4]. Because of the limitation of asexual propagation techniques due to the difficulty of producing large amounts of planting materials by cuttings, tissue culture, somatic embryogenesis, and other asexual methods, seed orchards took an important place in improving Korean pine [6]
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