Resin and resin canals in families and clones of Pinus radiata (D. Don)
Degree GrantorUniversity of Canterbury
Degree NameMaster of Forestry Science
Resin and resin canals are seen as defects in softwoods. The occurrence of these defects in appearance-grade radiata pine timbers causes devaluation. Living trees use resins and the resin canal networks as a defensive mechanism against pest and diseases by sealing wounds. This study determined the variation in resin quantity and resin canal features (density, percentage canal area, and canal size) between 2 year-old radiata pines grown from different genetic material. Out of an experiment for NZ radiata pine seed and clonal commercial deployment populations, 10 clones and 20 families were selected for the study. Near infrared (NIR) spectroscopy was used to estimate resin quantity whereas microscopy was used to assess resin canal features. Wood samples were heated to help gather resin at the cross-section followed by the collection of absorbance spectra with an NIR fibre optic probe. Wood sections (~20 μm thick) were imaged with a 2400 dpi flatbed scanner in polarised light. ImageJ software was used to analyse the images and to determine the resin canal features. Data were analysed with the R statistical software. Resin quantity obtained by NIR varied significantly (p < 0.01) between clones and families with average values of 2.71 and 3.68 (AU) respectively. Average canal density was 0.69 canal/mm2 for clones and 1.53 canal/mm2 for families (p < 0.01). Average percentage canal area was 1.13% for clones and 1.53% for families (p < 0.01). In both families and clones, resin canals were of homogenous size of approximately 0.02 mm2. There were weak genetic correlations between resin quantity and other canal features (r = 0.07 with canal density, r = 0.10 with percentage canal area). Resin canal frequency was strongly correlated with percentage canal area (r = 0.94). Variability between clones and families was present for all variables and summarised by the coefficient of variation (CV). Resin quantity had a CV of 61% and 51% for clones and families respectively. Resin canal features had CVs ranging between 10% and 31% across the families and clones. Resin quantity determined by NIR across the families and clones had 4% heritability, whereas the resin canal features had ~ 30%. The low heritability found for resin quantity could be due to the indirect NIR assessment. The resin features correlated favourably with modulus of elasticity and longitudinal shrinkage. The lesser the resin features the stiffer the wood and the lesser longitudinal shrinkage. Basic density and volumetric shrinkage had no correlation with resin features. These results suggest that, presently, radiata pine growers can identify genetic material that is more suited for high-value appearance-grade timber as well as maintaining improved wood properties (stiffness, density, growth, and form) in the markets.