Genetic Transformation in Liriodendron tulipifera L. (Yellow Poplar)

Abstract

Liriodendron tulipifera L. (yellow poplar) is one of the most common hardwood forest species in eastern North America, growing throughout the eastern United States and into southern Ontario, Canada. The species is most abundant and reaches its largest size in the lower Ohio River valley and in the Appalachian mountains of North Carolina, Tennessee, Kentucky, and West Virginia (Fowells 1965). Although it is an early-stage successional species on most sites, the rapid growth rate of yellow poplar and the large size of mature trees (up to 60 m) make it a dominant canopy species. These growth characteristics, along with its straight form, self-pruning ability, and wood of highly desirable working quality (Wilcox and Taft 1969), make yellow poplar a valuable timber species. It has been employed for furniture (mostly hidden parts), plywood, corestock, millwork, siding, and other light construction lumber. It is also used for such glue-wood products as chipboard, flakeboard, and oriented strandboard. Breeding programs have been established to take advantage of genetic variation in characteristics such as height growth (Farmer et al. 1983) and wood-specific gravity (Thorbjornsen 1961; Wilcox and Taft 1969). Bees are a primary pollinator of yellow poplar, and the species is known as a good honey producer. Yellow poplar is widely planted as an ornamental landscape tree, admired for its symmetrical leaves and yellow, green, and orange flowers. A number of horticultural cultivars have been described for the species (Santamour and McArdle 1984; see also Merkle and Sommer 1991 for more details).