Genetic variation and genotype by environment interactions of juvenile wood chemical properties in Pinus taeda L.

Genetic variation and genotype by environment interaction (GxE) were studied in several juvenile wood traits of 11 year-old loblolly pine trees (Pinus taeda L.). Wafer thin (200 mu m) samples from juvenile (ring 3) and transition (ring 8) wood of 12 mm increment cores were analyzed. Transition wood had higher a-cellulose content (46. 1 %), longer fiber (1.98 mm), and higher coarseness (0.34), but lower lignin (29.7%) than juvenile wood (cellulose 40.9%. fiber length 1.4 mm, coarseness 0.28 and lignin 30.3%). General combining ability variance for the traits explained 2% to 10% of the total variance, whereas the specific combining ability variance was negligible, except for a-cellulose content in transition wood (2%). Specific combining ability by site interaction variance explained from 5% (fiber length) to 37% (lignin) of the total variance. Weak individual-tree heritabilities were found for all the traits, except coarseness, which was moderately high in both juvenile (0.39) and transition wood (0.30). Full-sib and half-sib family heritabilities of traits ranged 0.29 to 0.72. Genetic correlations of wood quality traits with volume and stem straightness were weak, while favorable genetic correlations of lignin with cellulose, coarseness and fiber length were observed. Implications on forest tree improvement programs were discussed.