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Estimating Breeding Values and Genetic Gain of Cunninghamia lanceolata (Lamb.) Hook. var. konishii from a 27-Year Progeny Test with Messy Data.
Su, Susi Li-Ho
|關鍵字:||China fir;香杉;efficiency of blocking;border effect;progeny test;breeding value;best linear unbiased prediction (BLUP);heritability;區集效率;邊界效應;後裔檢定;育種價;最佳線性無偏差預測;遺傳率||出版社:||森林學系||摘要:||
本研究係針對臺灣的鄉土樹種香杉(Cunninghamia lanceolata (Lamb.) Hook. var. konishii)後裔檢定林分作育種價預測以及遺傳增益估計，共有18個單親家系。原始區集配置係採「逢機完全區集設計」(randomized complete block design, RCBD)，共有四個東西向緊鄰並排的縱向完全區集，但經由群內相關係數分析得知，區集配置應採二個南北向之橫向區集規劃較為妥當。更改區集配置後之數據結構呈不完全區集設計，且邊界效應嚴重影響邊緣木的橫向生長性狀，故剔除邊緣木後重作分析。
Eighteen open-pollinated (OP) families of a local variety of China fir (Cunninghamia lanceolata (Lamb.) Hook. var. konishii) were grown in a field trial to evaluate the magnitude of genetic parameter estimates and ranking of the parental clones, for growth (height, DBH, and diameter at basal area; DBA) and wood density traits up to 27 years. The field-trial layout was randomized complete block design (RCBD) with four adjacent south-north longitudinal blocks. After checking the intra-class correlations it was found that it would be better to divide the 4 east-west blocks into 2 south-north blocks, so that the long axis of the block is parallel to the contour. That made the field design incomplete blocks. It was also found that edge effects seriously influenced the stem diameter growth for the border trees. We therefore also deleted those seriously biased border trees from the data.
Statistical analyses showed second-year height and 27-year wood density were not influenced by environmental impacts, and there were no significant differences among families. Other growth traits (six-year height, 25-year height, 25-year DBH, 25-year DBA, 25-year stem volume, relative growth between second- and six-year heights, and relative growth between six- and 25-year heights) showed significant differences among families and among blocks. Height growth (second-year and 25-year heights) showed significant family by block interactions. Stem diameter growth (25-year DBH, DBA, and Volume) traits had no interactions at all.
Tree height between ages demonstrated substantial genetic correlation (0.61). Tree height and stem diameters of the same age also exhibited substantial genetic correlations (0.59). Twenty-seven-year wood density showed no family variation.
Twenty-five-year height showed high individual-tree heritability. Heritability estimates increased as the trees grew older. Height growth traits in general have higher heritabilities than stem diameter growth.
Using one unit of standard phenotypic deviation as selection differential to estimate genetic gain would result in 2.29m in 25-year height, 2.34cm in 25-year DBH, and 0.08m3 in 25-year stem volume. Using six-year height as an early-selection trait, indirect selection would result in 1.10m gain in 25-year height. This is equivalent to 0.18m per year, which is much higher than a gain of 0.09m direct selection in 25-year height.
No matter whether family effect is taken as “fixed effect” or “random effect”, arithmetical means and BLUP values showed high correlations (0.9231~0.9572), which implies that both are reliable estimates of the breeding values. Using BLUP values to rank families, five families were both selected into the top nine families for tree height at different ages. Using bi-character (25-year height and DBH) to adjust the estimate of breeding values of 25-year DBH is effective. The improvement magnitude of the top nine families is from 10.29% to 0.97%. This method was therefore proven to be a superior strategy of multi-trait selection. Current research results provide a useful reference for genetic selection of China fir in the future.
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