Genetic considerations in cloning western hemlock

Graduation date: 1984Using clones to regenerate a species new to clonal reforestation presents the forest manager with many problems. A number of interrelated and interdependent research and development activites are needed to answer these technical questions. Network diagraming was used for scheduling research activities and for indicating interdependencies among activities. The resultant diagram, although developed specifically for western hemlock [Tsuga heterophylla (Raf.) Sarg.], represents a program which may be useful for other species in which clonal reforestation is considered to be potentially appropriate. Once the network diagram was completed, several activities were examined in detail by experiments. The first group of activities dealt specifically with clonal variation (and its components) for five rooting traits and demonstrated that clonal variation was due to both genetic and C effects (persistent environmental effects). The potential bias to genotypic values of clones due to C effects is significant, but heritability and gain estimates are only slightly biased. The five rooting traits were highly heritable (H = 0.87 to 0.92), and predicted genetic gain from clonal selection was substantial. Genetic correlations between pairs of traits were generally high (0.66 to 0.99); therefore, when selecting for any one trait, correlated responses can be expected in other traits. The second group of activities examined components of clonal variation for juvenile height (HT) as well as associations between rooting traits and subsequent height growth of rooted cuttings. As with the rooting traits, C effects in HT were a significant proportion of the total genetic variation. HT was found to be under strong genetic control (H = 0.81), and genetic correlations between HT and rooting traits ranged from 0.37 to 0.59. A selection index containing both juvenile height, HT, and a rooting trait, VOL, would result in the application of selection pressure to both traits simultaneously