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Variance components of tree height (HT) and stem diameter at 1.3 m above the ground (DBH) were investigated for the eight open-pollinated families of Zelkova serrata (Thumb.) Makino planted with three different initial planting spacings in a progeny test site, Chiba, Japan. Parent–offspring correlations were also evaluated by using these families and their mother trees. The smallest values of HT and DBH were observed in the narrowest initial planting spacing (1.10 x 1.10 m) compared to those in medium (1.30 x 1.36 m) and wide (2.00 x 1.80 m) spacings, suggesting that adverse effects of competition with neighboring trees occurred on both height and radial growth. Similar to HT and DBH, the initial planting spacings also affected the genetic parameter estimates: the ratio of family variance component to total phenotypic variance showed the highest value in narrow initial planting spacing for both HT and DBH. Thus, family variance component might include competition effects, leading to biased genetic parameter estimates. In contrast, parent–offspring correlation coefficients showed the highest value in wide initial planting spacing where competition effect might be smaller. Therefore, the growth traits of Z. serrata might be inherited from the parent to the offspring when competition effect was small.
Four hundred and sixty individual families of Pinus radiata, representing all provenances and populations in a 1978 seed collection, plus a local seed orchard control, were planted together in 1980 in a large trial in southern New South Wales, Australia. Provenance means and genetic parameters for growth measured at ages 3, 8 and 26 years plus stem straightness, branch angle and nodality at age 26 years are reported. Large provenance differences were apparent for all traits. The two island provenances, Cedros and Guadalupe, were significantly inferior to the mainland provenances and, due to competition effects, very few trees survived to age 26. Within the mainland provenances, the performance of Año Nuevo and Monterey was almost identical, with Cambria being less vigorous. The best performing seedlot for all traits was the local control. Differences between populations within the mainland provenances were apparent for diameter at age 26 within Año Nuevo and Cambria but not Monterey. Año Nuevo also showed population differences for stem straightness. Heritabilities for early growth were similar within Año Nuevo and Monterey but by age 26, the heritability for diameter was higher in Monterey. Within Cambria, heritabilities for growth and tree form at age 26 were close to zero. Genetic correlations between traits showed similar patterns for each of the mainland provenances, with the exception of correlations with stem straightness within Año Nuevo. Results are discussed in light of recent molecular studies of genetic architecture, levels of inbreeding in the native stands and possible effects of this inbreeding.
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