Place of Wood Specific Gravity in the Development of Advanced-Generation Seed Orchards and Breeding Programs

Abstract Data from thinnings of 11 genetic tests with an average age of 10 years and from 364 eight-year-old second-generation selections were analyzed to provide an estimate of gain from one cycle of selection for wood specific gravity. Utilizing mid-parent, mature, wood specific gravities and progeny juvenile wood specific gravities, coefficients of genetic prediction, CGP = 0.55 and 0.41, were calculated for the genetic test thinning sample and second-generation selection sample. Expressed as a percentage of the mean, gain from selection was calculated to be 2.6 percent. A strategy was also developed to include wood specific gravity in the North Carolina State Cooperative's second-generation loblolly pine (Pinus taeda L.) improvement program. High heritability figures indicate little need to develop extensive family information for wood specific gravity in advanced-generation breeding programs.