Seed Source Selection for Improvement of Growth and Wood Traits in 10-Year-Old Fraxinus griffithii C. B. Clarke Trees Planted in Northern Highlands of Thailand

Fraxinus griffithii C. B. Clarke is introduced from Taiwan to Thailand by the Royal Project Foundation beginning of the 1980s for highland rehabilitation. To improve the growth traits and tree form characteristics, a tree breeding program for this species has been initiated. In the present study, we evaluated the among seed sources variations in growth traits (diameter at 1.3 m above the ground [DBH] and tree height) and wood traits (basic density [BD], modulus of elasticity [MOE], modulus of rupture [MOR], and compressive strength parallel to the grain [CS]) of 10-year-old F. griffithii trees originated from 15 seed sources planted in highland areas of Thailand. The mean values of measured trees were 7.25 cm in DBH, 11.59 m in tree height, 0.76 g/cm3 in basic density, 9.74 GPa in MOE, 100.78 MPa in MOR, and 38.46 MPa in CS, respectively. Broad-sense heritability ranged from 0.13 to 0.16 in growth traits and 0.02 to 0.85 in wood traits. As a result of principle component analysis and cluster analysis, 15 seed sources were classified into three groups. Of the three groups, one showed good performance in both growth and wood traits. Significant phenotypic and genetic correlations were found between growth traits and between wood traits. However, no significant correlations were found between growth and wood traits. Based on the results, it is concluded that progeny with good performance of both growth and wood traits can be produced from the combinations of superior seed sources tested in the present study.