Primers in this study.

Agarwood is a resin produced by wounded Aquilaria plants. Aquilaria sinensis (Lour.) Gilg  is the original plant source of agarwood in China. Formic acid combined with Botryosphaeria rhodina A13 (FAA13) induces the formation of artificial agarwood as an effective integrated induction method. However, its formation mechanism is still unclear, and the harvesting time of agarwood has not been elucidated. In this work, we analyzed FAA13-induced artificial agarwood and leaves at different time points within one year based on endophytic fungal community, expression of related genes, and secondary metabolites. The induction process by FAA13 was divided into two stages. In agarwood, we found that fungal diversity and relative abundance decreased in stage 1 but increased in stage 2. Additionally, genes related to 2-(2-phenylethyl) chromones synthesis were mainly expressed in stage 1, while those related to sesquiterpene synthesis were mainly expressed in stage 2. The primary differential metabolites between the two stages were the content of ethanol-soluble extractives (EEC%) in the agarwood and epi-friedelinol and friedelin in the leaves. EEC% in agarwood stabilized and was at a high level in stage 2. At the same time, we observed friedelin rose rapidly from a plateau or after a slight decline, and epi-friedelinol continued to rise. We found similar results in artificial agarwood induced by combining formic acid with Fusarium sp. A2 (FAA2). The content of epi-friedelinol and friedelin in leaves can be used as an index to judge agarwood’s harvesting period during the integrated method’s induction process. The appropriate harvesting period for agarwood should be determined by collecting leaves in stage 2 (8 months later) without damaging the tree and assessing whether friedelin enters a rapid rise from the plateau stage by rapidly determining epi- friedlinol and friedelin content.

沉香（Agarwood）是受伤沉香属植物分泌的树脂。白木香（Aquilaria sinensis (Lour.) Gilg）是中国沉香的基原植物。甲酸联合玫瑰色葡萄座腔菌A13（FAA13）是一种高效的综合诱导方法，可诱导人工沉香形成。然而，其形成机制尚未明确，沉香的采收期也未得到阐明。本研究基于内生真菌群落、相关基因表达及次生代谢物，对一年内不同时间点的FAA13诱导人工沉香及对应叶片样本进行了分析。FAA13的诱导过程可分为两个阶段：在沉香组织中，真菌多样性及相对丰度在第一阶段呈下降趋势，第二阶段则显著上升；此外，2-(2-苯乙基)色酮类合成相关基因主要在第一阶段表达，而倍半萜合成相关基因则主要在第二阶段表达。两个阶段的主要差异代谢物为沉香中的乙醇浸出物百分含量（EEC%），以及叶片中的表羽扇豆醇与羽扇豆酮。沉香中的乙醇浸出物百分含量在第二阶段趋于稳定并维持在较高水平。与此同时，我们观察到羽扇豆酮含量从平台期或小幅下降后快速升高，而表羽扇豆醇含量则持续上升。在甲酸联合镰孢菌属A2（FAA2）诱导的人工沉香中，我们得到了相似的实验结果。在综合诱导法的诱导过程中，叶片中的表羽扇豆醇与羽扇豆酮含量可作为判断沉香采收期的指标。沉香的适宜采收期可通过以下方式确定：在不损伤植株的前提下采集第二阶段（诱导后8个月）的叶片，通过快速检测表羽扇豆醇与羽扇豆酮的含量，判断羽扇豆酮是否从平台期进入快速升高阶段。