A Strategy for the Third Breeding Cycle of Loblolly Pine in the Southeastern U.S

A strategy for the North Carolina State University Industry Cooperative Tree Improvement Program’s third-cycle breeding for loblolly pine (Pinus taeda L.) was developed to provide genetic gain in the short-term as well as to maintain genetic diversity so that long-term genetic gains will also be possible. Our strategy will be to manage a hierarchy of three populations, each at a different level of intensity. The mainline population will consist of about 160 selections that are available to each cooperator in a given geographic region (i.e. recruitment population). These populations will be managed as subdivided breeding populations (40 sublines of 4 trees each) primarily to provide for long-term genetic gain and diversity The most intensively selected and managed hierarchy will be the elite populations. A highly selected group of trees (approximately 40 selections) will be managed to provide short-term genetic gain for each member’s program. A third hierarchy will be the genetic diversity archives managed to preserve and ‘1 Geneticist and Professor, Cooperative Tree Improvement Program, Box 8002, Department of Forestry, North Carolina State University, Raleigh, NC 27695-8002, USA. ‘? Research Geneticist and Adjunct Professor, USDA Forest Service, Southern Forest Experiment Station, Texas A&M University, College S t a t i o n , T X 7 7 8 4 3 2 5 8 5 , USA. Silvae Genetica 47,4 (1998) , breed genotypes with extreme breeding values for individual traits (not necessarily for all traits combined) as an insurance population for environmental or selection criteria changes in