Variation in the Incidence of Resin-filled Shakes and Wood Density among Open-pollinated Families of Pinus elliottii Planted at Four Different Sites

SYNOPSIS A study on the incidence and severity of resin-filled shakes was carried out on 36 open-pollinated families established at four different sites. The objectives were to study the distribution of shakes within and between trees, and how it is affected by genetics and environment. In general a clear pattern in the variation among families was observed suggesting that there is some genetic influence. However, between the four different sites the among-family patterns of variation in resin shake propensity, differences between trees within families, and the distribution within tree stems, were extremely variable and inconsistent. From this it is evident that some genotypes seem to respond differently to the influences of environment. Resin shakes often occurred in the basal part of the tree stem, often extending into the stump, but the frequency of occurrence varied considerably between sites. Shakes occurring higher up in the stem were often associated with large knots, knot clusters and forks. The t...