Genetic parameters and gains for growth and wood properties in Florida source loblolly pine in the southeastern United States

One hundred and thirteen open-pollinated families from Florida source loblolly pine (Pinus taeda L.) were tested in four states in the southeastern United States. Heritabilities and genetic correlations were estimated for volume, specific gravity, and latewood percentage at three different growth stages: juvenile (ages 0-10 years), mature (11-17 years), and total (0-17 years). Heritabilities of growth traits (0.09-0.11) were consistently lower than for wood property traits (0.16-0.33). Growth traits for Florida loblolly exhibited high genotype x environment interaction (r(B) = 0.44), whereas wood properties did not (r(B) = 0.90). The higher heritabilities and genetic stability across environments make wood properties amenable to genetic manipulation through breeding programs. In contrast, the high genotype x environment interaction of growth traits for Florida loblolly pine requires more research to understand the possible implication of these effects on breeding programs. Trait-trait and age-age genetic correlations were determined for growth and wood properties. Strong positive age-age correlations were present for latewood percentage, volume, and specific gravity. Weak negative trait-trait genetic correlations existed between specific gravity and volume across ages (-0.13 to -0.43). No genetic correlation existed between latewood percentage and volume, while a moderate favorable genetic correlation existed between latewood percentage and specific gravity (0.47 to 0.59). Genetic gains in volume and specific gravity were compared for various types of selection. In one type, forward selection of the top 20 individuals (of 3484) based on 17-year volume, resulted in a 20.5% genetic gain in volume; however, a concomitant loss of -6.4% also occurred in specific gravity. If a selection index was used to hold specific gravity constant, a gain in total volume of 14% was obtained.