Journal of Heredity 2003:94(5)
© 2003 The American Genetic Association 94:392-398
On the Number of Genes Controlling the Grass Stage in Longleaf Pine
From the USDA Forest Service, Southern Research Station, the Southern Institute of Forest Genetics, 23332 MS Highway 67, Saucier, MS 39574-9344 (Nelson and Kubisiak); Karmanos Cancer Institute, Room 615 HWCRC Building, Wayne State University, 110 E. Warren Avenue, Detroit, MI 48202 (Weng); Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, School of Renewable Natural Resources, Baton Rouge, LA 70803 (Stine); and University of Georgia, Warnell School of Forest Resources, D.W. Brooks Drive, Athens, GA 30602 (Brown).
Address correspondence to Dr. Nelson at the address above.
The grass stage is an inherent and distinctive developmental trait of longleaf pine (Pinus palustris), in which height growth in the first few years after germination is suppressed. In operational forestry practice the grass stage extends for two to several years and often plays a role in planting failures and decisions to plant alternative species. Interspecies hybrids involving loblolly (P. taeda) and slash (P. elliottii var. elliottii) pines have been investigated as a means to produce planting stock with improved early height growth and to develop backcross populations for advanced generation breeding. We have reevaluated data from several interspecies populations, with the objective of estimating the number of genes contributing to the difference in first-year height growth between longleaf and loblolly pines. Estimates based on means and variances of parental and interspecies hybrid and backcross families suggest a minimum of 4 to 10 genes with standard errors less than half the estimates. These results suggest that the grass stage has evolved through the accumulation of alleles at several loci, each with small effects on various components of first-year height growth. Given the complexity of the grass-stage trait, tree breeders may need to combine genetic marker analysis with recurrent backcross breeding to efficiently develop longleaf pine planting stock for improved reforestation.