Evaluation of Atlantic Coastal and Piedmont sources of loblolly pine (Pinus taeda L.) seedlings and their hybrids for growth and cold hardiness
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1999-08-30
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Abstract
Seedlings of 60 loblolly pine (Pinus taeda L.) families representing four populations, Atlantic Coastal, Piedmont, Coastal x Piedmont, and Piedmont x Coastal were compared for early seedling growth and cold hardiness. The objectives of this study were to examine seedling growth of the four populations in a greenhouse environment and cold hardiness of the four populations in controlled environments (preconditioning) designed to mimic environmental conditions in the Piedmont areas planned for deployment. In addition family differences within each population for seedling growth characteristics (height, root collar diameter, and volume index) and cold hardiness were evaluated. The Atlantic Coastal population was the tallest in average, followed by the Coastal x Piedmont hybrids, the Piedmont x Coastal hybrids, and the Piedmont population. All improved populations were superior in seedling growth to the unimproved Piedmont checklot. The height superiority appears to be related to length of the growing season in the provenance of origin. There was not much distinction between populations for root collar diameter although the improved populations were all superior to the checklot. Differences in volume index were related to family rather than population effects, and differences in height contributed more to volume growth than differences in diameter. Cold injury was not significantly different based on preconditioning treatments, but differences in cold hardiness were related to population and families. Hybrids behaved in a manner similar to the maternal parent. Heritability estimates were moderate for injury assessment, indicating that cold injury is under strong genetic control. Coastal families had the highest narrow sense heritability for injury (h2=0.45) followed by the Piedmont families and Coastal x Piedmont hybrids. Coastal x Piedmont hybrids had the highest heritability for survival followed by the Piedmont families. There was a strong genetic correlation between height and cold hardiness at the population level. The taller trees from Atlantic Coastal population tended to suffer more damage than the shorter trees from Piedmont population. Seven of the top ten families ranked for height were in the bottom 1/3 of families ranked by injury. These tended to be Coastal or Coastal x Piedmont families. Seven of the top twenty families ranked for height fell into the middle 1/3 of families ranked by injury. These tended to be hybrid families, although a few Coastal families were present. Based on these early results, it appears that intraspecific hybridization between the two sources of loblolly pine may provide taller trees similar to Coastal parent and cold hardiness similar to the Piedmont parent. It would appear that there is an advantage to deploy Piedmont x Coastal hybrids on the more adverse (e.g. colder Piedmont, cold area) sites. On the miler sites, deployment of Coastal x Piedmont or hardy Coastal families might be appropriate. There are risks associated with deploying families that are not hardy on these sites. Excessive mortality would cancel out the growth advantage if non-hardy tree genotypes were deployed.
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MS
Discipline
Forestry
