|Micropropagation of Sandalwood|
Santalum is a genus of woody flowering plants, commercially valuable because of its highly valued fragrant heartwood, which contains sandal oil that is used in perfumes, cosmetics, medicines and also in incense sticks industries (Srinivasan, et.al, 1992). Most members of this genus are either trees or shrubs and root parasites which photosynthesize their own food but tap the roots of other species for water and inorganic nutrients (Wikipedia, the free encyclopedia.mht). Brand J (2005) stated that the best hosts for sandalwood are nitrogen fixing trees because growth depends on the amino acid availability and the host plant should not compete with the sandalwood for nutrients. Santalum has over 30 genera and 400 species in the tropical and temperate parts of the world.
Fruit is produced after three years and viable seeds are mostly available after five years. Like most forest tree species, seed propagation is common to Santalum, however, seedlings are extremely heterozygous due to out-crossing. Vegetative propagation via grafting, air layering and root suckers can be used but the production of clones is inefficient and time consuming (Shrimati et.al., 1995).
For centuries, sandalwood has been an important commercial industry in the Pacific. Sandalwood species are grown in island countries like: Santalum macgregorii (in PNG), Santalum austroledonicum (New Caledonia and Vanuatu) and Santalum yasi (Fiji and Tonga). Santalum album, however, is also planted and grows well in most Pacific countries from New Caledonia to French Polynesia and the Cook Islands.
The long-term exploitation of sandalwood has had a serious impact on the industry and there is now an urgent need to undertake some extensive planting. To achieve the level of planting required using conventional propagation methods would be extremely inefficient and time-consuming. An effective micro propagation protocol would greatly benefit the development of the sandalwood “industry” and increase productivity. As stated by Beck and Dunlop (2001) plant tissue culture based biotechnology has been employed to generate quality planting material with many forest tree species.
The sandalwood research in the CePaCT aims to establish a micro propagation protocol that would address initiation, multiplication and rooting of the Santalum sp. Multiple shoots of Santalum yasi, Santalum album and hybrid have been induced from nodal shoot segments derived from adult trees at Colo-i-Suva and juvenile plants excised from seed-derived plants in the Centre for Pacific Crops and Trees (CePaCT) nursery. Both explants taken from the adult trees and the nursery plants were cultured on MS (Murashige & Skoog, 1962) medium supplemented with different concentrations of α-naphthalene-acetic acid (NAA) and 6-benzylaminopurine (BA). Three different treatments are currently being investigated for root establishment, namely: pulse treatment of explants followed by soil planting, culturing explants on MS medium supplemented with host plant extracts; culturing explants on MS medium.