Variation and genetic control of wood density

VARIATION AND GENETIC CONTROL OF BASIC WOOD DENSITY IN Shaw Research Centre, Sappi Forests (Pty) Ltd., P. O. Box 473, Howick, 3290, South Africa CAMCORE Cooperative. North Carolina State University, Raleigh, U.S.A. , genetic control, basic wood density, densitometry, non-destructive sampling is a closed-cone pine that has a rather narrow, but long, distribution in Mexico. It ranges from approximately 16 N latitude, is generally restricted to humid, sub tropical to near temperate sites, with deep, fertile clay soils, and an estimated mean annual precipitation of 1000 to 2500 mm. Approximately one million hectares of plantations have been established in the tropics and sub tropics for saw-timber and paper products. The majority of the forests are located in southern Africa with South Africa having more than 300,000 hectares under operational management. Since 1986 the CAMCORE Cooperative has sampled 25 provenances and 624 mother trees of in Mexico. The CAMCORE collections represent the most complete coverage of the species natural distribution to date. During December 1990, a series of five trials of open-pollinated family/provenance seedlots were established adjacent to each other at Maxwell in KwaZulu-Natal, South Africa. These trials are 11 years old and offered a unique opportunity to sample material from the entire geographic range of the species to determine to what extent wood properties are under genetic control at the provenance, family and individual tree level. Nine hundred and seventy-two individual trees were sampled non-destructively by removing 12 mm increment cores for the evaluation of wood anatomical properties using densitometry and image analysis. Preliminary results from wood density assessments indicate that provenance differences are significant and that the trait is under strong genetic control at the family level. One of the disadvantages of wood in relation to other raw materials used in manufacturing industries is its great variability. However from a