Aquilaria hirta is one of the agarwood tree species in Malaysia that produces a unique resinous wood and essential oil used in perfumery, medicinal, cosmetic and religious ceremonies. Currently, it has been listed as vulnerable (VU) and threatenad species in the IUCN Red List. This study aims to characterise the morphology of A. hirta via scanning electron microscopic analysis, and to identify the volatile chemical compounds of the wood and its essential oil using gas chromatography-flame ionisation detector and gas chromatography-mass spectrometry analyses. Aquilaria hirta was identified by the presence of hirsute on the abaxial side of leaves and midrib. The field emission scanning electron microscope analysis showed plant vessel pits can be seen in the healthy wood images compared with resinous wood images due to presence of resin and microorganisms. A total of 19 compounds were identified in resinous A. hirta wood consisting of 5.97% sesquiterpenes and 20.32% oxygenated sesquiterpenes. The major compounds are kessane, γ-cadinene, α-caryophyllene, β-caryophylene and caryophyllene oxide. There were 35 compounds found in A. hirta oil comprising 0.45% monoterpenes, 23.51% sesquiterpenes and 19.53% oxygenated sesquiterpenes. Major compounds detected were γ-cadinene, nor-ketoagarofuran, allo-aromadendrene, γ-gurjunene and β-gurjunene. This study provides a reference for the identification of A. hirta species based on morphology evaluation and volatile chemical compounds profile of the essential oil and wood.

Aquilaria genus is an important source of agarwood and is widely used as incense, perfumery and ingredients in traditional medicines. The study investigated the genes and pathways controlling the molecular mechanism of A. malaccensis agarwood under controlled environment. Two transcriptome libraries were sequenced from mRNAs of both healthy and infected stem samples of A. malaccensis using Illumina sequencing. Total of 10,734,590 and 8,298,918 reads for both infected stems libraries and 6,274,184 reads for healthy stem library were identified. A total of 370,707 unigenes were functionally annotated using the gene ontology analysis. Infected white stem recorded higher reading of unigenes distribution in process related to plant defence mechanism compared to healthy stem. The de novo assembly and the gene ontology annotation data suggested that the infected white stem involved in plant defence response and produced agarwood compound. This study provided promising and valuable sequence resources for future genomic studies from stem of A. malaccensis as well as in depth study on molecular mechanism of agarwood formation and plant related defence responses.