Genetic variation of seedling growth traits of open-pollination families of Pinus tabulaeformis

The analysis of seedling growth traits from open-pollination families from 3 seed orchards and 1 superior provenance of Pinus tabulaeformis was made in Shaanxi Provence .The results indicated that stands and families exited abundant genetic variation and the variance components of families were more than those of stands .Families in different seed orchards and different families in same seed orchard had highly significant difference in height and diameter.The height growth of the best family progeny was one time more than the worst one .There were significantly difference among the 1 000-seed weights and the range of variation were 20.04 -65.10g .1000-seeds weight were close correlations with diameter but light correlations with seedling height .Through meritability of diameter and height were very high .Through using growth index , there were 46 excellent families be selected primarily and the expected genetic gains of height and diameter were 16.32 %-27.86 % and 6.39 %-23.08 % respectively .The selection effect was very striking .[ Ch , 7 tab .12 ref .]