Abstract
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 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 future generations. The improved efficiency of this breeding strategy along with the reduction in population sizes compared to the current program, will result in a substantial reduction in effort by individual cooperators. The increase in selection intensity from reducing the population sizes and the increased rate of breeding made possible by mating fewer trees will substantially increase gains in subsequent generations. While the most intensive effort will be devoted to those populations providing immediate genetic and financial gain, the long-term well-being of the genetic resource will be maintained by judicious management of all three hierarchies.
Keywords
Elite breeding populations,
genetic gain,
mating designs
Citation
McKeand, S.E.; Bridgwater, F.E. 1998. A Strategy for the Third Breeding Cycle of Loblolly Pine in the Southeastern U.S. Silvae Genetica 47, 4(1998)
