Oil yield and composition of young Santalum yasi in Fiji and Tonga

Abstract

Santalum yasi, a sandalwood native to Fiji and Tonga, is a tree crop of significant economic potential for these countries. Development of a plantation industry underpinned by a breeding program is a high priority for industry development. Gathering information on heartwood development, oil yield and oil composition is a critical step for the domestication and tree breeding of the species. Oil yield and composition were determined for 86 Santalum core samples using gas chromatography and combined gas chromatography/mass spectrometry. Most (67) cores were from the lower boles of individual trees of S. yasi, with smaller samples of S. album and S. album × S. yasi, both of which are also commonly grown in Fiji and Tonga, and S. austrocaledonicum was included for comparison. Although the ages of the trees were unknown, they are likely to have been between 10 and 20 years. Relationships among traits, including solvent-extracted oil yield, oil composition, lower bole diameters under and over bark, and heartwood diameter, were examined. Yield was highly variable (0.05-11.8%) and only weakly correlated with underbark diameter at 30 cm above ground. Oil yield and percent composition of santalol oil components were strongly positively correlated. For those trees with oil yields >1% w/w, the oil composition was generally favourable relative to the international standard for S. album oil, with large proportions of santalols, particularly β-santalol. The study confirms that both harvesting and selection for genetic improvement of S. yasi trees younger than 20 years old are likely to be suboptimal, with unreliable heartwood and oil development. Further study of heartwood and oil development, both within individual trees and among genotypes in common-garden trials with known genetics and controlled environments and hosts, is a high priority. The development of an international standard for S. yasi, supporting the growth of a niche market for the product, is also recommended.

Domestication provides the key to conservation ofSantalum yasi– a threatened Pacific sandalwood

“…There is often a temptation or necessity to generate earlier cash income, however, and trees are commonly harvested at around 15 years, at which time only a modest amount of heartwood has usually developed. A survey of trees in Fiji and Tonga in 2018 indicated that harvesting at this age risks losing substantial income, with incomplete heartwood defvelopment evident (Bush, Brophy et al 2020); similar findings were made by Doran et al (2005), who examined young-aged (10-20-year-old) sandalwood including S. album, S. yasi and their hybrid in Fiji and Tonga, and by Jones et al (2006), who studied 14-17-year-old planted S. album at Kununurra, Western Australia. Harbaugh and Baldwin (2007), which examined multiple populations of each species.…”

Participatory value chain study for yasi sandalwood (Santalum yasi) in Fiji

“…Santalum yasi appears to have a higher proportion of βsantalol in its oil than S. album (Doran et al 2005;Bush, Brophy et al 2020). As β-santalol is chiefly responsible for some of sandalwood's signature aromas (Baldovini et al 2011), this trait may be used to positively differentiate the product.…”

“…Oil quality is an equally important trait for sandalwood buyers, processors and consumers, with the most highly desired oils meeting the International Organization for Standardization (ISO) standard for East Indian sandalwood oil (ISO 2002-3518) of 41-55% α-santalol and 16-24% β-santalols. Two studies on oil constituents (Doran et al 2005;Bush, Brophy et al 2020) have indicated that pure yasi may be particularly rich in β-santalol, with individual tree samples frequently exceeding the ISO S. album standard. According to one French perfume chemist, the quality of a sandalwood oil for perfume may be enhanced by its minor fragrant constituents as much as by its α-and β-santalol content and also negatively affected by undesirable minor constituents, which may give 'off-characteristics' to fragrance, give rise to allergic responses such as contact dermatitis, or are listed as undesirable in product pharmacopeia.…”

“…It would be useful to produce an official monograph with information on yasi oil, make this available to international buyers and end users, and use it to develop a separate standard for yasi oil. Although some sandalwood industry experts are concerned about hybrid oil quality, research indicates that S. album × S. yasi produces a high-quality oil (Doran et al 2005;Bush, Brophy et al 2020). Some sandalwood traders believe that it will be in the interests of Fijian and Tongan growers to keep local S. yasi as pure as possible to develop niche markets, a strategy that will have positive outcomes for the conservation of the species ) and is also being pursued for S. austrocaledonicum in Vanuatu (Page et al 2020).…”

Sandalwood trade and development in Papua New Guinea

“…The mean levels of αand β-santalol in S. macgregorii found by Page, Jeffrey et al (2020) were lower than their respective levels in Santalum yasi Seem. from Fiji and Tonga (Bush, Brophy et al 2020) and S. album in Australia (planted) and Sri Lanka (Brand et al 2012;Subasinghe et al 2017). For Santalum austrocaledonicum Vieill., much variation in the level of santalol was found within and between sites in Vanuatu, but several sites in both Vanuatu and New Caledonia demonstrated higher santalol levels, equivalent to S. album (Braun et al 2005;Page et al 2010;Butaud 2015) and higher than any S. macgregorii population.…”