Differences in wood density and growth of fertilized and nonfertilized loblolly pine associated with a mutant gene, cad-n1

A rare mutant allele (cad-n1) of the cad gene in loblolly pine (Pinus taeda L.) causes a deficiency in the production of cinnamyl alcohol dehydrogenase (CAD). Effects associated with this allele were examined by comparing wood density and growth traits of cad-n1 heterozygous trees with those of wild-type trees in a 10-year-old open-pollinated family trial growing under two levels of fertilization in Scotland County, North Carolina. In all, 200 trees were sampled, with 100 trees for each fertilizer treatment. Wood density measurements were collected from wood cores at breast height using X-ray densitometry. We found that the substitution of a cad-n1 for a wild-type allele (Cad) was associated with a significant effect on wood density. The cad-n1 heterozygotes had a significantly higher wood density (+2.6%) compared with wild-type trees. The higher density was apparently due to the higher percentage of latewood in the heterozygotes. The fertilization effect was highly significant for both growth and wood density traits. This study indicates that the cad-n1 allele could be a valuable gene to the pulp and paper industry for the purpose of enhancing pulp yields by increasing wood density.