Agarwood is the resinous part of the injured tree of the Aquilaria species of the Thymelaeceae family, Qi-Nan is a type of agarwood that forms easily and benefits from a shortened inducing time, noted for features like its substantial resin, (2-phenylethyl) chromone and 2-[2-(4-methoxyphenyl) ethyl] chromone content. Although the content of agarotetrol in Qi-Nan is very low, it is still an important indicator for the agarwood quality. A validated method was developed to precisely quantify both agarotetrol and two aforementioned chromones, as well as ethanal extracts, within Qi-Nan to explore how the inducing time (half a year, one year, and two years) and different clones (YYZ, AS, RH, XGY) affect agarwood quality. Different clones and inducing time both have significant effects on agarwood quality. The agarwood quality of Qi-Nan does not necessarily improve with a longer inducing time. YYZ, AS, and RH clones reached to the best agarwood quality after two years of induction. The ethanol extracts content was among 46.82 ~ 48.59%, two chromones were among 10.57% ~ 14.05% after two years of induction. However, for XGY clone, the quality of agarwood after one year of induction was better than that after two years, which reached to the highest ethanol extracts (51.49%) and two chromones content reached to 12.43% and 12.91% after one year of induction. Therefore, for different clones of Qi-Nan, harvesting should be conducted at different time of induction for agarwood formations, which has theoretical implications for the cultivation and industrial development of cultivated Qi-Nan agarwood.

Phytoplasmas are a group of wall-less, unculturable prokaryotic pathogenic bacteria that colonize the phloem of plants and are transmitted by piercing–sucking insects. As a typical tropical island province in China, Hainan Island has abundant biodiversity due to its unique geographical location and climatic conditions, which provide a favorable ecological environment for the survival and propagation of phytoplasmas, which infect different hosts, cause different symptoms, or belong to different subgroups. Based on host species, disease symptoms and 16Sr subgroups, 69 representative phytoplasma records from four 16Sr groups have been identified on Hainan Island, showing rich diversity in host range and pathogen species. The diversity of plant hosts and the evolutionary relationship of phytoplasmas not only affect the occurrence and prevalence of phytoplasma-related diseases but also bring great challenges to the epidemic monitoring, detection, diagnosis and prevention management of these diseases. This review summarizes current research progress on host diversity, phylogenetic evolution, mixed infection, diversity of transmission vectors, and geographical isolation differentiation, as well as adaptive evolution of phytoplasmas on Hainan Island. Furthermore, the challenges brought by plant host diversity and phylogenetic evolution to disease monitoring, diagnosis and prevention management are discussed. This review aims to provide a comprehensive theoretical basis for the in-depth study of phytoplasma-related diseases on Hainan Island, and to offer practical guidance for scientific monitoring, early warning and comprehensive prevention and control of these diseases.

Mytilaria laosensis is a fast–growing and high–yielding timber tree species widely grown in the southern subtropical region of China (Yu et al. 2023). In September 2024, a survey was conducted in Yingde City, Guangdong Province, southern China. Sapling stem canker symptoms were found on M. laosensis, and the incidence rate was 33.12% (investigated 1561 trees and infected 517 trees). The symptoms included dark brown necrotic spots that were sunken and shrunken, with cracked cortex and yellowing leaves. The epidermis was stripped from four stem pices (∼0.5 cm) between the healthy and infected tissues, the pieces were disinfected with 75% alcohol for two minutes, rinsed three times with sterile water, and dried for 10 minutes. They were then placed in Petri dishes on potato dextrose agar (PDA) medium and cultured at 28°C in the dark for 2–3 days to obtain pure cultures. Then, monosporic cultures were obtained (isolates MLP112, MLP414, MLP424, and MLP511). The fungal colonies were initially composed of white hyphae, after 5 days became gray and after 10 days turned black. Immature conidia were hyaline, aseptate, ellipsoid, thick–walled, and mature conidia elliptic or oblong, simple septate, dark brown in color, 19.3–31.3 μm in length and 9.2–15.7 μm in width, (mean length=23.9 μm, width average=11.9 μm, N=40), length–to–width ratio was 2.0. Based on morphological characteristics the fungus was temptatively identified as Lasiodiplodia theobromae (Alves et al. 2008). To confirm the indentity of the isolates, the internal transcribed spacer (ITS) region of rDNA, translation elongation factor 1 (tef1) and beta tubulin genes were amplified with the universal ITS (White et al. 1990), EF1–α (Stielow et al. 2015) and β–tubulin (Glass & Donaldson 1995) primers, respectively, and sequenced. The obtained sequences were deposited in Gen Bank (ITS: PV855669, PV855670, PV855671, PV855672; EF1–α: PV903164, PV903165, PV903166, PV903167; β–tubulin: PX564918, PX564919, PX564920, PX564921). BLAST results showed 100% similarity with reliable references of L. theobromae (ITS, OR116087.1; EF1–α, OR536247.1; β–tubulin, MT212400.1). To fulfill Koch’s postulates, 5 mm diameter mycelial plugs of PDA cultures were inoculated into eight M. laosensis stem segments, while four stem segments were inoculated with sterile PDA plugs and served as a control. Both ends of stem segments were sealed with paraffin, Segments were incubated at 28°C and 80% relative humidity. Within 5 to 7 days, inoculation sites exhibited obvious dark brown to black lesions and epidermal necrosis, consistent with symptoms of natural infections. The control stems remained asymptomatic. The fungus was isolated from the tissue and identified as L. theobromae based on morphology and DNA sequencing (ITS, tef1 and β–tubulin). The host range of L. theobromae include more than 500 plants species (Hattori Y. et al. 2023). To the best of our knowledge, this is the first report of L. theobromae causing sapling stem canker on M. laosensis in China. The results of this study will help to develop management strategies of M. laosensis sapling stem canker.