No abstract

Agarwood is a highly fragrant and valuable resin produced in certain species of Aquilaria and Gyrinops genera of Family Thymalaeaceae. This resin is produced as a first line defense mechanism to protect the tree stem from microbial invasions. Due to the extensive use in cosmetics, medicines, religious and cultural activities, the demand for agarwood resins in Europe, Middle East and South-east Asian regions is very high. Gyrinops walla, locally known as Walla patta is the only naturally growing agarwood producing species in Sri Lanka and it is distributed in the humid lowland forests of the wet zone and intermediate zones of low elevations. The ability of producing agarwood resins in G. walla was scientifically discovered in 2012. Parallel to that, there were reports of large scale of poaching and illegal transport of this species with certain involvements of the foreign nationals.This study was conducted to identify the variation of agarwood resin contents of G. walla trees growing under different climatic and geographical conditions in Sri Lanka and to identify the relationship of resin contents with tree growth parameters. For this purpose, 64 trees growing in eight distinct areas, viz., Horawala, Kalatuwawa, Kalawana, Karandana, Maliboda, Mirigama, Neboda and Yagirala belong to wet and intermediate zones of low country were collected. Collected tissues were size reduced and the resins were collected by solvent extraction method. Colours of both resinous tissues and extracted resins were determined using a standard method. One-way ANOVA was conducted to identify the significance of resin contents among different regions and Pearson correlation was tested between resin contents and tree growth parameters.The colour of the resinous tissues and extracted resins varied from light brown to dark brown and yellow to dark brown respectively. The highest average resin content (4.92%) was recorded from Maliboda while the lowest (2.19%) was recorded from Kalawana. One-way ANOVA did not report significant differences of resin contents between different locations. Significant correlations were also not found between resin contents and tree diameter and height. According to the resin content analysis of naturally growing trees, it was revealed that the best trees can be identified at Maliboda area to collect seeds for making the next generation in the plantation establishment.

Gyrinops walla, a member of Thymelaeaceae family produces valuable agarwood resin used for religious, cultural and medicinal purposes in many countries. It is formed as a self-defense mechanism to any stress caused physical, chemical or biological agents. Since a comparison of agarwood formed due to natural and artificial causes was not done previously, the present study was conducted to fulfill that objective. For this reason, 150 G. walla trees growing in nine locations (Horawala, Kalatuwawa, Karandana, Maliboda, Neboda, Yagirala, Mirigama, Kalawana and Suriyakanda) of wet zone, Sri Lank were selected for collecting agarwood resins formed due to natural causes. Medium size G. walla trees growing in Horawala and Kalawana were selected for formation of agarwood resins in artificial manner. Insertions of iron nails, galvanised tubes, polyvinyl chloride tubes and polypropylene tubes were used as the mechanical method; sodium chloride and sodium bi-carbonate were used as the chemical method and forest mushroom mycelia was used as the biological method to form agarwood resins. Three replicates were used for each agent and agarwood tissues were collected after 12 months of inoculation. Solvent extraction was used to extract agarwood resins and constituent analysis was done by GC-FID method. It was possible to identify 21 compounds belonging to seven classes, viz., agarospirol, vetispirane, selinene, cardinane, guaiene, eremophilane, 2-(2-phenylehtyl)-chromone and fatty acids from naturally formed agarwood resins. However, 28 compounds were present in the resins formed due to artificial methods belonging to nine classes. Among them agarofuran, and valencane were only found in the artificially formed resins. Agarospirol and agarofuran are the most important compounds that produce the characteristic aroma of agarwood resins. However, agarofuran was not observed from the naturally formed agarwood resins. All compounds identified in this study are present in the agarwood resins of Aquilaria species grown in Southeast Asian countries. The results confirmed that artificially formed agarwood in G. walla chemically bears the same quality of naturally produced agarwood.