Presence of Actinomycetes in agarwood tissues of Aquilaria crassna: A preliminary study

Abstract

Agarwood is a valuable resin produced inside certain tree species of the family Thymalaeaceae distributed in the Asian region. Agarwood production occurs as a defense mechanism when the trees are under physical or biological stresses. However, the formation of agarwood resins in significant extractable quantities due to natural stress conditions is rare; therefore, the farmers use various methods to induce its formation artificially. Certain fungal species such as Fusarium and Aspergillus become more popular among them to produce high-quality agarwood. However, studies are rare on using other microbial organisms such as Actinomycetes, which exhibit properties of both bacteria and fungi. Among the agarwood-producing species, Aquilaria crassna is one of Asia's most commonly planted species for agarwood production. This species was introduced to Sri Lanka in 2012 for mid and lower elevations of the wet zone. Due to the lack of studies on agarwood resin formation by non-fungal microbial methods, the present study attempted to identify the presence of Actinomycetes species in agarwood resinous tissues of A. crassna. Agarwood resinous tissue samples were collected from four plantations in the wet zone of the country. Surface sterilized, small sized tissues were placed on starch casein agar medium and incubated at room temperature for ten days. Using the morphological and microscopic characteristics, it was possible to identify Nocardia, Psuedonocardia, and three Streptomyces species with varying abundance. The species level should be confirmed using molecular analysis, and their potential for agarwood resin formation inducement should be tested by re-inoculating to the healthy A. crassna trees.