GENETIC-PARAMETERS FOR BOLE VOLUME IN LONGLEAF PINE - LARGE-SAMPLE ESTIMATES AND INFLUENCES OF TEST CHARACTERISTICS

Data from 17 progeny test/seedling seed orchard sites of longleaf pine (Pinus palustris MILL.) containing a total of 901 open-pollinated fam ilies and 40,801 trees were analyzed to obtain precise genetic paramet er estimates for hole volume at age 8, to evaluate genetic gains in se edling seed orchards, and to determine relationships between genetic p arameter estimates and the test characteristics of survival, site prod uctivity, and statistical precision. Estimates of bole volume heritabi lity based on individual-test analyses (biased heritability)averaged 0 .311 (range 0.143 to 0.570 across the 17 tests). Thirty-four pairwise combinations of tests were also analyzed to estimate unbiased heritabi lities and Type B genetic correlations (r(B)). The mean estimates for these parameters were 0.205 and 0.675, respectively. In most cases, ge netic parameter estimates were not significantly related to characteri stics of the tests. Type B genetic correlations, however, were signifi cantly larger (indicating less genotype x environment interaction) whe n test pairs were in the same geographical planting zone (r(B) = 0.747 ), than when they were in different (east vs. west) zones (r(B) = 0.61 0). Planting zone x family interaction will need to be considered in f uture selection and seed deployment decisions. Nevertheless, even if t his interaction is ignored, genetic gain in eight-year volume from low intensity (50%) roguing of families and individuals in the seedling s eed orchards is expected to average around 11%. Gain in a 1.5 generati on clonal seed orchard containing the best individual in each of the t op 25 (2.8%) of the families is expected to exceed 35%.