Variation of Wood Density Traits in Rooted Cuttings and Seedlings of Loblolly Pine
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Date
2003-12-31
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Abstract
Wood samples were collected from 10-year-old loblolly pine (Pinus taeda L.) rooted cuttings and seedlings from nine full-sib families resulting from a 3x3 factorial mating design. The field design consisted of two sites with six blocks per site in a randomized complete block design. In the spring of 2001, 12 mm increment cores were taken from approximately 1600 trees, and measurements of height and diameter were taken at the age of 10 ½ years. No significant differences were found between rooted cuttings and seedlings for specific gravity or growth traits, but sites significantly differed for growth traits. Significant family variation was found for both growth and specific gravity. Genetic parameters were estimated for wood specific gravity and growth traits for both seedlings and rooted cuttings. Heritabilities for specific gravity were generally high, and estimates from rooted cuttings were higher than from seedlings. Specific gravity was found to be negatively correlated with height. Clones were less variable than full-sib seedlings for specific gravity. These results suggest that gains in specific gravity could be made in breeding programs through the use of clonal testing during breeding and the deployment of superior clones.
Wood strips from the increment cores were then measured using x-ray densitometry. Seedlings and rooted cuttings did not differ significantly for overall latewood density, earlywood density or latewood percentage of the whole core, but overall wood density did differ significantly based on seven growth rings. Half-sib and full-sib loblolly pine families did not display significant variation, but clones within families differed significantly in wood density, latewood density, and latewood percentage, indicating the greater potential for gains from clonal selection. Heritabilities for composite ring density traits were found to be moderate to high, indicating the potential for gains in wood density through selection of families or clones. Individual ring analysis revealed that the wood density of rings 1-4 was highly correlated with wood density through ring 7, suggesting that selection of juvenile wood density could be made at an early age.
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genetic parameters, wood density, rooted cuttings, loblolly pine
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Degree
MS
Discipline
Forestry
