Can fungi and related microorganisms induce agarwood formation?

Abstract

Presented at the 20th International Forestry and Environmental Symposium

November 2015

Imalka Hitihamu, Upul Subasinghe, Preeni Fernando

Gyrinops walla Gaertn is the only agarwood forming species naturally growing in Sri Lanka. This species, belongs to the family Thymalaeaceae is commonly growing in the low country wet zone of Sri Lanka where the annual rainfall is high. Being very valuable due to the pleasant aroma, agarwood resin is extensively used in cosmetic manufacturing, cultural and religious activities. It is produced as a result of a self-defense mechanism towards any stress caused by several factors which can be physical, chemical and biological. However, use of fungal species to artificially induce agarwood resin formation in Aquilaria species is common in the Southeast Asian region. The present study aimed to explore the possibility of inducing agarwood formation in G. walla trees using Actinomycetes species.

Actinomycetes species were isolated from fresh agarwood resinous tissues of G. walla and associated soils by culturing them in the laboratory. In order to do that, the Actinomycetes species growing with other fungal species in the culture plates were identified using their colony characteristics, reproductive structures and then pure cultures were prepared. Two g of Actinomycetes with solid agar medium was inoculated into non-agarwood formed G. walla trees under aseptic conditions. Observations were made for the agarwood resins in the stem tissues at 10 cm intervals above and below the inoculated points at monthly intervals. Discolouration of the stem tissues was recorded in the field. Resin contents (w/w%) were determined by solvent extraction and the constituents were analysed using GC-MS technique. Stem tissue discolouration varying from yellow to black was observed form the first month after the inoculation. Resin contents varied from 0.03% to 1.66% and high resin contents were observed in dark coloured tissues usually extracted closer to the inoculation points. Moreover, 12 constituents were identified which were also common to the agarwood resins extracted from the Aquilaria species. This study is the first attempt in Sri Lanka investigating the potential of Actinomycetes species as inducing agents of agarwood formation and results reveal that Actinomycetes species are effective microorganisms in production or agarwood resins in G. walla

Extraction of agarwood resins from Walla patta

Agarwood resin, considered to be the most valuable plant product has been kept as a secret in most of the time by the distillers at homestead and industry levels in southeast Asian countries where the Aquilaria trees are grown. After the discovery of the presence of agarwood resins in Walla patta naturally growing in Sri Lanka, the Forest Management Group of University of Sri Jayewardenepura, headed by Dr. Upul Subasinghe started trials on agarwood resin extractions to support the industry and homestead level distillers that are expected to be formed in near future. 

The trials were conducted using a locally manufactured mini-distillation facility with varying water:agarwood ratio, distillation time and the particle size. The results proven that all the selected parameters above have significant impacts on both the oil content and quality which was tested by using GC-MS and GC-FID methods.

Now those results are being further tested using an imported agarwood distillation facililty of medium-scale from Thailand to identify the best energy type and the resin quality improvement methods.

Financial assistance for this project was rendered by the National Research Council and Sadaharitha Plantations Limited via Public-Private-Partnership Programme.