As widely recognized, agarwood formation in Aquilaria trees is induced by external wounding. Because agarwood usually harbors specific microbes, the function of microbes in agarwood formation has been debated for almost a century. In this study, two wounding methods, the burning-chisel-drilling method (BCD) and the whole-tree agarwood-inducing method (Agar-Wit), were used under the non-contamination of environmental microorganisms. After pyrosequencing the small rRNA subunits of the wounds induced by the BCD and Agar-Wit, no substantial variation was observed either in fungal and bacterial enrichment and diversity or in the relative abundances of taxa. By contrast, significant variations in fungal and bacterial communities were detected following the partial tree pruning (PTP)-wounding. The wound-induced sesquiterpene biosynthesis and vessel-occlusion formation, however, were found to be similar in all types of wounded trunks. We thus infer that wounding in the absence of variations in microbial communities may induce agarwood formation. This result does not support the long-standing notion that agarwood formation depends on microbes.

Dalbergia odorifera, a critically endangered tree species, produces heartwood containing a vast variety of flavonoids. This heartwood, also known as Chinese rosewood, has high economic and medicinal value, but its formation takes several decades. In this study, we showed that discolored wood induced by pruning displays similar color, structure, and flavonoids content to those of natural heartwood, suggesting that wounding is an efficient method for inducing flavonoid production in D. odorifera. Transcriptome analysis was performed to investigate the mechanism underlying wounding-induced flavonoids production in D. odorifera heartwood. Wounding upregulated the expression of 90 unigenes, which covered 19 gene families of the phenylpropanoid and flavonoid pathways, including PAL, C4H, 4CL, CHS, CHI, 6DCS, F3’5’H, F3H, FMO, GT, PMAT, CHOMT, IFS, HI4’OMT, HID, IOMT, I2’H, IFR, and I3’H. Furthermore, 47 upregulated unigenes were mapped to the biosynthesis pathways for five signal molecules (ET, JA, ABA, ROS, and SA). Exogenous application of these signal molecules resulted in the accumulation of flavonoids in cell suspensions of D. odorifera, supporting their role in wounding-induced flavonoid production. Insights from this study will help develop new methods for rapidly inducing the formation of heartwood with enhanced medicinal value.

Four new 2-(2-phenylethyl)chromone derivatives (1–4) were isolated from the EtOH extract of Chinese agarwood produced via the whole-tree agarwood-inducing technique, coming from Aquilaria sinensis (Lour.) Spreng. (Thymelaeaceae). Their structures were elucidated by extensive spectroscopic methods, such as UV, IR, MS, 1D as well as 2D NMR. All of the isolates were then assessed for their anti-inflammatory activities on lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW 264.7. Compound 1 exhibited significant inhibitory activity with an IC₅₀ value of 4.6 μM.

Recently, Qi-Nan germplasm, the germplasm ofAquilariaspecies that easily forms agarwood, has been widely cultivated in Guangdong and Hainan Provinces in China. Since the morphological characteristics of Qi-Nan germplasm are similar to those ofAquilariaspecies and germplasm is bred by grafting, it is difficult to determine the source species of this germplasm by traditional taxonomic characteristics. In this study, we performed a DNA barcoding analysis of 58 major Qi-Nan germplasms as well asAquilaria sinensis,A.yunnanensis,A.crassna,A.malaccensisandA.hirtawith 5 primers (nuclear gene internal transcribed spacer 2 (ITS2) and the chloroplast genesmatK,trnH-psbA,rbcLandtrnL-trnF). This field survey in the Qi-Nan germplasm plantations in Guangdong and Hainan Provinces aimed to accurately identify the source species of Qi-Nan germplasm. According to the results, ITS2 andmatKshowed the most variability and the highest divergence at all genetic distances. This ITS2+matKcombination, screened for with TaxonDNA analysis, showed the highest success rate in species identification of the Qi-Nan germplasm. Clustering in the phylogenetic trees constructed with Bayesian inference and maximum likelihood indicated that the Qi-Nan germplasm was most closely related toA.sinensisand more distantly related toA.yunnanensis,A.crassna,A.malaccensisandA.hirta. Therefore, this study determined that the source species of the Qi-Nan germplasm isA.sinensis.

Dalbergia odorifera T. Chen is traditionally referred to as „Dalbergiae Odoriferae Lignum” in traditional Chinese medicine. Its quality is typically assessed subjectively based on colour and texture observations and lacks a universal grading system. Our objective was to establish a relationship between heartwood colour and the content of key constituents, including total flavonoids, six specific flavonoids, alcohol-soluble extracts, and volatile oils, to assess their impact on heartwood quality. Substantial correlations were observed between the colour depth (L*), red–green direction (a*), and yellow–blue direction (b*), as well as the content of the extract, volatile oil, total flavonoids, naringenin, formononetin, pinocembrin, and isoliquiritigenin. Specifically, a* was correlated with the extract, total flavonoids, and isoliquiritigenin, whereas b* was correlated with the extract, volatile oil, total flavonoids, naringenin, formononetin, pinocembrin, and isoliquiritigenin. The results suggested that L*, b*, and chemical composition indices, such as extract, volatile oil, total flavonoids, and naringenin, could serve as primary criteria for classifying the quality of medicinal materials. This is consistent with market classification based on colour and texture, which facilitates material identification and guides the cultivation, harvesting, and processing of D. odorifera. This study provides a scientific foundation for its future development and use.

The heartwood of Dalbergia odorifera T. Chen has garnered significant attraction due to its high medicinal, aromatic and timber values; however, its formation mechanism remains unexplored. This study utilized the sapwood (N-B), transition zone (N-T), and heartwood (N-H) of the xylem of 15-year-old, naturally heartwood-forming D. odorifera to observe the nuclei of parenchyma cells, revealing that no living cells were specialized in synthesizing the secondary metabolites of heartwood in the N-H. Additionally, analysis of gene expression patterns across different compartments indicated that differentially expressed genes (DEGs) involved in the synthesis of secondary metabolites of heartwood were primarily up-regulated in the N-T, suggesting that the pattern of heartwood formation in D. odorifera follows the Type-I (Robinia-Type) model, wherein secondary metabolites are synthesized in situ in the ray parenchyma cells of the N-T, followed by programmed cell death (PCD) leading to heartwood formation. Furthermore, DEGs related to ethylene biosynthesis and signaling pathways were up-regulated in the N-T, suggesting that ethylene signaling may play a critical role in regulating the heartwood formation process of D. odorifera. Treatment of suspension cells with polyethylene glycol (PEG) and an ethylene synthesis inhibitor (AVG) further confirmed that ethylene acts as a key signaling molecule in the formation of heartwood-like material in D. odorifera. This study provides initial insights into the molecular mechanisms underlying heartwood formation in D. odorifera and offers a foundation for developing heartwood formation and promotion technologies.