Screening and identification of fungi associated with natural and artificially induced agarwood from aquilaria malaccensis

Aquilaria malaccensis is a tropical tree which produces expensive resinous heartwood (agarwood) through naturally or artificially-induced injury or fungal infection. Fungi are commonly observed as the main microbial component responsible for agarwood formation. Until now, an effective formulation containing fungi-producing agarwood is not reported yet. The difference that exists between natural and artificially induced agarwood may be due to the different fungi diversity. Thus, a comparison between these two samples in terms of agarwood quality and fungi diversity is inevitable in order to determine effective agarwood inducers. Moreover, the comparison may show the quality of artificially induced agarwood to be potentially equal to natural agarwood based on fungal infection. This study focused on the analysis of agarwood volatile compounds from natural and artificially induced agarwood, as well as the isolation, screening, and identification of the fungi species associated with agarwood from both sources. The best inoculant performance was screened based on GCFID analysis of four months induced agarwood with respective commercial inoculant. Inoculant, Ino A, was proven to stimulate production of benzaldehyde, 4-phenyl-2-butanone, β selinene, and agarospirol. One year artificially induced agarwood (M1 and M2) showed competent sesquiterpene production such as agarospirol (4.31% and 0.301%), β-selinene (0.769% and 0.643%), aromadendrene (none and 1.976%), and β-agarofuran (none and 0.176%) compared to high-quality natural agarwood. Agarospirol was detected in all agarwood samples but higher in artificially induced agarwood. Artificially induced agarwood exhibited more fungi isolates compared to natural agarwood samples. Meanwhile, isolation of fungi from healthy wood as control enabled to grow the most of six isolates from each respective agarwood samples. Macroscopic observation and microscopic examination enabled isolated fungi to be group into ten. It was anticipated that eight groups of fungi isolated were identified in both natural and artificially induced agarwood associated with agarwood formation using culturing and sequencing of ITS regions of the fungi isolated from wood samples. In this study, fungi isolated were identified from Lasiodiplodia sp., Aspergillus sp., Fusarium sp., Schizophyllum sp. and Polypolares Order. Phanerochaete chrysosporum and Schizophyllum commune were discovered as new fungi associated with Aquilaria malaccensis agarwood. From the phylogenetic analysis, five clades of taxa were formed based on 1000 bootstrap values which supported previous genomic identifications