Heritability Estimates For Loblolly Pine Wood Specific Gravity Based On Control-pollinated Genetic Tests

Specific gravity is an important wood quality trait that affects both the quality and quantity of pulp and solid wood properties. To determine the heritability and age-age relationships for specific gravity, increment cores were collected at DBH (1.4 m) from four control-pollinated loblolly pine genetic tests that were at least 20 years old. These tests contained 93 families representing 23 different parents. Unextracted specific gravity was determined on core segments that included the first five years from the pith, rings six to 20 years and the total core. The estimates of general combining ability were significant for all age segments in each test; however, none of the estimates for specific combining ability were significant. Family heritability estimates for the first five years from the pith averaged 0.58 and ranged from 0.38 to 0.75 among the four genetic tests. For the six to 20-year core segments, family heritability estimates averaged 0.73 and ranged from 0.62 to 0.79. The coefficient of genetic prediction between the two age segments averaged 0.50. Selection at age five for specific gravity would be approximately 68 percent as efficient as direct selection to increase age six to 20-year specific gravity.

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Author(s): William J. Lowe, Thomas D. Byram

Publication: Tree Improvement and Genetics - Southern Forest Tree Improvement Conference - 1995