A Clonal Testing Program for Loblolly Pine Plantation Forests

Abstract

Forest products companies would like to grow clonal plantations of superior loblolly pine (Pinus taeda L.) to improve fiber yields. Feasibility depends on developing efficient propagation techniques and finding superior clones. Horticultural stem-cutting propagation methods and micropropagation techniques are being coupled to test, preserve, multiply, and ultimately deploy clones. Outstanding clones are being found through a series of field tests; each beginning with a superior full-sibling cross from a 40-year-old breeding program. Clones are first screened for rooting ability, and the top 25% to 35% of clones are then established on four sites. Since maintenance of juvenile phase tissue is critical to perpetuating high rooting rates and fast subsequent growth, each clone is preserved as a set of serially propagated hedges and as cold-stored microshoots. As field tests age, better-performing clones are multiplied gradually. Large-production stock blocks of juvenile hedges consequently may be established from both rooted cuttings and microshoots as soon as field tests end. Clones producing large numbers of long branches have been noted for their potential value as fast-growing ornamentals. Since such characters are opposite those desirable for forestry, these clones would need to be preserved, multiplied, and marketed separately from clones for plantation forests.