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Spatial structures of differing levels of genetic homogeneity and spacing in loblolly pine stands were evaluated by estimating the spatial autocorrelation at the stand level. Four different levels of genetic homogeneity including clones, full-sib families, half-sib families, and a seed orchard mix were randomized into two spacings (3.0 × 6.1 m, 538 trees/ha; and 1.5 × 6.1 m, 1,077 trees/ha). The detrended stem diameters were assessed using a spatial autocorrelation parameter contained in a simultaneous autoregressive model and a standardized Moran's I statistic for the residuals. The results showed that 12.5% of the plots were positively autocorrelated and 5.0% of the plots were negatively autocorrelated at an α level of 0.10. It was found that spacing had an effect on both significant positive and negative spatial autocorrelations. A majority of positively and negatively autocorrelated plots were located in the wider spacing and closer spacing, respectively. No particular trend in terms of different levels of genetic homogeneity was noted except in one specific clone when planted at a wider spacing. Characterization of the spatial autocorrelation structure between individual trees at the stand level will aid in development of better models to represent on-the-ground stand conditions. [ABSTRACT FROM AUTHOR]

Forking defects and ramicom branching were assessed in a cloned full-sib family of loblolly pine (Pinus faeda L). The proportion of forking ranged from 13 to 21% across four test sites with a mean of 17%. Romkorn branching incidence averaged 24% and varied from 18 to 31% over all sites. There were significant differences among clones within this family for all traits studied. The estimated done mean repeatabilities were moderately high for forking defects (0.67-0.86). Through single trait selection with a selection differential of 4%, the proportion of trees with forks and romkorn branches could be reduced 10 and 13%, respectively. Low to moderate unfavorable genetic correlations were found between growth traits and forking defects (0.12-0.45), suggesting that selection for either trait alone will negatively affect the genetic response for the other. No significant environmental correlations were found between forking and growth. A moderate significant positive genetic correlation between stem forking and romkorn branching indicates that both traits may be partially controlled by the same genes and could be improved simultaneously. Strategies are discussed for within-family selection to capture more gain for increased growth and reduced stem forking for the breeding of loblolly pine. [ABSTRACT FROM AUTHOR]

Progeny from 48 elite parents of loblolly pine (Pinus taeda L.) were bred in a disconnected diallel mating design and were planted at four sites across the lower coastal plain of the southeastern United States. Height, dbh, volume, fusiform rust incidence (caused by the fungus Cronartium quercuum [Berk.] Miyabe ex Shirai f. sp. fus~forme), stem forking, stem sweep, branch angle, branch diameter, branch frequency, and a sawtimber potential score were measured after six growing seasons. There were significant differences among families for all traits measured. Individual-tree narrow-sense heritability estimates ranged from 0.06 to 0.22 and half-sib family-mean heritability estimates ranged from 0.73 to 0.98. Height and volume were the traits most highly correlated with the sawtimber potential score of individual trees. From multiple regression, 79% of the variation in sawtimber potential breeding values can be attributed to variation in volume, rust incidence, stem sweep, and forking breeding values. The potential dollar value of loblolly pine was increased as much as 162% over local checks when both volume and sawtimber potential were used to select the 10 best parents from the population. Implementation of a selection index on currently measured traits is a promising opportunity to make gains in the proportion of sawtimber produced from improved germplasm of loblolly pine in the southeastern United States. [ABSTRACT FROM AUTHOR]

Background: The plastic response of fine roots to a changing environment is suggested to affect the growth and form of a plant. Here we show that the plasticity of fine root growth may increase plant productivity based on an experiment using young seedlings (14-week old) of loblolly pine. We use two contrasting pine ecotypes, "mesic" and "xeric", to investigate the adaptive significance of such a plastic response. Results: The partitioning of biomass to fine roots is observed to reduce with increased nutrient availability. For the "mesic" ecotype, increased stem biomass as a consequence of more nutrients may be primarily due to reduced fine-root biomass partitioning. For the "xeric" ecotype, the favorable influence of the plasticity of fine root growth on stem growth results from increased allocation of biomass to foliage and decreased allocation to fine roots. An evolutionary genetic analysis indicates that the plasticity of fine root growth is inducible, whereas the plasticity of foliage is constitutive. Conclusions: Results promise to enhance a fundamental understanding of evolutionary changes of tree architecture under domestication and to design sound silvicultural and breeding measures for improving plant productivity. [ABSTRACT FROM AUTHOR]

Journal of Forestry, 2021, 215 doi:10.1093/jofore/fvz036 Erratum Advance Access publication June 3, 2019 215 Copyright © 2019 Society of American Foresters Erratum The Evolution of a Seedling Market for Genetically Improved Loblolly Pine in the Southern United States, Journal of Forestry Steven E. McKeand https://doi.org/10.1093/jofore/fvz006 The Acknowledgments in this article were incomplete. They have now been updated to the following: Acknowledgments: This work was supported by members of the North Carolina State University Cooperative Tree Improvement Program. [Extracted from the article]