Geographic and Phenotypic Variation in Heartwood and Essential‐Oil Characters in Natural Populations of Santalum austrocaledonicum in Vanuatu

Abstract

Phenotypic variation in heartwood and essential-oil characters of Santalum austrocaledonicum was assessed across eleven populations on seven islands of Vanuatu. Trees differed significantly in their percentage heartwood cross-sectional area and this varied independently of stem diameter. The concentrations of the four major essential-oil constituents (alpha-santalol, beta-santalol, (Z)-beta-curcumen-12-ol, and cis-nuciferol) of alcohol-extracted heartwood exhibited at least tenfold and continuous tree-to-tree variation. Commercially important components alpha- and beta-santalol found in individual trees ranged from 0.8-47% and 0-24.1%, respectively, across all populations, and significant (P<0.05) differences for each were found between individual populations. The Erromango population was unique in that the mean concentrations of its monocyclic ((Z)-beta-curcumen-12-ol and cis-nuciferol) sesquiterpenes exceeded those of its bi- and tricyclic (alpha- and beta-santalol) sesquiterpenes. Heartwood colour varied between trees and spanned 65 colour categories, but no identifiable relationships were found between heartwood colour and alpha- and beta-santalol, although a weak relationship was evident between colour saturation and total oil concentration. These results indicate that the heartwood colour is not a reliable predictive trait for oil quality. The results of this study highlight the knowledge gaps in fundamental understanding of heartwood biology in Santalum genus. The intraspecific variation in heartwood cross-sectional area, oil concentration, and oil quality traits is of considerable importance to the domestication of sandalwood and present opportunities for the development of highly superior S. austrocaledonicum cultivars that conform to the industry's International Standards used for S. album.

Phytochemistry of the heartwood from fragrant Santalum species: a review

“…75, 90, 92) has recently allowed a significant variability to be shown in tree populations growing in New Caledonia [43] and Vanuatu. [68] One of the most sophisticated techniques for authenticity assessment is gas chromatography coupled with isotope ratio mass spectrometry (GC-IRMS). When applied to individual constituents of sandalwood oils, the measurements of d O, taken alone or together, offer attractive possibilities.…”

Reproductive biology of three commercially valuable Santalum species: development of flowers and inflorescences, breeding systems, and interspecific crossability

“…More modest planting activities have also recently been recorded in China (S. album) (Xiaojin et al (in press)), India (S. album) (Jeeva et al 1998) and Vanuatu (S. austrocaledonicum) (Page et al 2010a). Programmes also exist for development of cultivars with improved productivity and oil quality (Page et al 2010b).…”

Stimulation of Western Australian sandalwood (Santalum spicatum) oil production using multiple treatments

“…There are gaps in the literature regarding what influences heartwood production. It has been theorised that heartwood may be formed in sandalwood as a reaction to stress (Page et al, 2010;Rai, 1990), however no concluding evidence has yet been discovered.…”

“…Although not found in sandalwood, MeSA is produced in some plants when they experience stress (De Boer & James, 2003;James & Price, 2004;Van Den Boom et al, 2004;Walling, 2000). As it has been observed that heartwood is formed in sandalwood as a reaction to stress (Page et al, 2010;Rai, 1990), it was theorised that by artificially introducing MeSA to the sandalwood tree, in response the tree would produce greater quantities of heartwood.…”

“…This indicates that Kylie Reserve has the most favourable conditions of the three plantations utilised for this study for production of the highest quality oil. Further studies will need to explore this inverse relationship, and the relationship between sandalwood tree stress and oil quality, in addition to the known relationship between stress and oil yield (Page et al, 2010;Rai, 1990).…”