Genetic Parameter Estimates for Seedling Dry Weight Traits and Their Relationship with Parental Breeding Values in Slash Pine
Abstract:Seedlings from 64 open-pollinated families of slash pine were grown in low and high nitrogen (N) treatments (5 ppm and 50 ppm) in raised outdoor boxes. Destructive harvests were conducted 3, 6, and 10 mo after sowing to measure dry weights of needles, stems, tap roots, and lateral roots. Genetic parameters (i.e., family-mean heritabilities, Type A genetic correlations, and Type B genetic correlations) were estimated for dry weight traits at each destructive harvest. Family-mean heritability estimates were high for traits in all harvests (most exceeded 0.60). Type A genetic correlation estimates, measuring the commonality of gene effects between two traits measured in the same individuals (i.e., in the same N treatment), were not significantly different from + 1 for most dry weight traits at each harvest. Type B genetic correlation estimates, measuring the commonality of gene effects between two traits measured in different individuals of the same families (i.e., across the two N treatments), were also near + 1 for most traits. Genophenotypic correlations (a single-trait prediction index) between family means of seedling dry weight traits and parental additive genetic breeding values for 15-yr field volume growth were relatively high at the 3-mo measurement (mostly higher than 0.40), but the values were lower for the 6- and 10-mo measurements. Because most pairs of dry weight traits from the same harvest were highly genetically correlated with each other, correlations between field breeding values and those predicted from two-trait indices were only slightly higher than single-trait indices. However, when traits were combined across the three harvest dates, correlations between field breeding values and predictions from two-trait indices increased to over 0.50. The best early selection indices were more effective at identifying the bottom-ranked families than the top-ranked families. An early selection technique using these traits would not be efficient enough to supplant long-term field testing, but could be used to reduce the size of field tests via early culling of poor-performing families or to screen infusion candidates for minimal breeding value requirements. For. Sci. 41(3):546-563.
Document Type: Journal Article
Affiliations: Associate Research Scientist, Department of Forestry, University of Florida, Gainesville, FL 32611
Publication date: August 1, 1995
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