Agarwood formed by insect (Neurozerra conferta) infestation involves fungal confection dominated by Neocosmospora solani with enzymatic profiles indicative of the involvement in resin development

Abstract

It is believed that the larval stage infestation by Neurozerra conferta Walker of Aquilaria malaccensis trees followed by fungal infections assists in higher-quality agarwood formation. However, it remains unclear what these intricate interactions offer for higher-grade agarwood formation. In the earlier studies, fungal diversity associated with agarwood has been identified and their role in agarwood formation has been fairly well established. However, these studies cover a broad aspect of agarwood fungal diversity and interactions but lack specificity regarding insect infestation, particularly since agarwood can be obtained either naturally through insect-inflicted injuries or artificially induced by different methods. The present study therefore specifically examines the culturable fungal associates in resinous agarwood formed due to the infestation by N. conferta. A total of 12 fungi were isolated belonging to four fungal families, namely Endomelanconiopsidaceae, Hypocreaceae, Nectriaceae, and Trichocomaceae. Internal Transcribed Spacer (ITS) sequencing identified the isolates as Endomelanconiopsis microspore, Fonsecaea monophora, Fusarium incarnatum, Fusarium sp., Neocosmospora solani, Penicillium sp., and Trichoderma cf. harzianum. Screening for enzyme activity revealed the isolates with the highest rate of xylanase activity compared to cellulase and tannase activity. However, most of the fungal isolates could produce the tannase enzyme, implying its potential in overcoming the plant's defense process. N. solani exhibited abundance and, displayed variations in colony morphology as well as enzyme activities. Therefore, our findings provide a basis for understanding N. solani, as the significant fungal microbe contributing to the agarwood formation via resin development in the N. conferta infested A. malaccensis trees.