Isozyme Heterozygosity, Phenotypic Family Stability, and Inter-Family Competition Among Seedlings of Loblolly Pine

Five open-pollinated families of loblolly pine were used to produce a seedling population, which was used to establish a competition diallel containing 20 family combinations. Each subject family was grown in combination with all other families at four subject family to competitor ratios (i.e., 16.67:83.33, 33.33:66.67, 83.33:16.67 and 100.0:0.00). The change in competitor genotype and competitor frequency significantly influenced subject tree growth. Twenty-four enzymes representing 41 isozyme locus were examined per mother-tree and 16 enzymes representing 19 isozyme loci were examined in the progeny of each mother-tree. Percent heterozygosity per mother-tree, mean percent heterozygosity per mother-tree family and percent heterozygosity per isozyme loci per mother-tree family were correlated to six-month-old seedling measurements obtained from the competition diallel to test the relationship between heterozygosity, fitness and variability. Twelve correlations with individual isozyme heterozygosity were significant at the 0.05 level (four more than expected by chance). Relationships between isozyme heterozygosity, phenotypic stability and competition are discussed. Additional keywords: horizontal starch gel electrophoresis, genotype x environment interactions, balancing selection, Pinus taeda.

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Author(s): Gerald A. Tuskan, A. E. Wiselogel

Publication: Tree Improvement and Genetics - Southern Forest Tree Improvement Conference - 1987