First Report of Colletotrichum plurivorum Causing Anthracnose on Panax notoginseng in Wenshan, China

Panax notoginseng, a perennial herb (Li et al. 2025), is economically important to Wenshan Prefecture,Yunnan Province, China (Hu et al. 2026). In July 2025, irregular dark brown lesions with yellow margins were observed on P. notoginseng leaves in Wenshan City (23.41°N, 104.18°E), with an incidence approximately 8%, affecting a planting area of about 4 ha. Symptoms developed in the middle or along margins of young leaves. For isolation, 15 symptomatic leaves from 3 fields were excised into 5 × 5 mm pieces, surface-sterilized (15 s in 75% ethanol, followed by 20 s of 2% NaOCl, rinsed 3 times with sterile water), and plated on potato dextrose agar (PDA) at 25 °C for 3 days. Thirteen single-spore strains were obtained from 7 samples. All strains were identified as Colletotrichum spp. by morphology (Damm et al. 2019). Aerial mycelium was dense and felty. Colonies were white, gray, to brown, with gray, brown to black reverse and even margins. Ascomata were formed after 3 weeks, solitary, superficial or immersed, black, subglobose to pyriform, measured 58.1 to 196.9 × 52.4 to 180.3 (n = 50). Asci were cylindrical or clavate, broadly truncate at the base, 8-spored, measured 61.6 to 137.4 μm × 14.9 to 26.4(n = 30). Ascospores were biseriately arranged, aseptate, hyaline, fusiform, measured 17.9 to 29.2 × 6 to 10.3 μm (n = 100). The conidia were cylindrical, measured 12.5 to 24.7 × 3.9 to 10.1 μm (n = 100). Appressoria were loosely distributed, pale to medium-brown, with smooth walls, nearly spherical to oval, and intact or lobed margins, measuring 13.4 ± 3.2 × 8.8 ± 2.4 μm (mean ± SD), length/width ratio 1.6 (n = 30). Strains LSAW4-3-2, LSAW4-3-6, LSAW5-4-1, LSAW6-1-2, and LSAW9-1-2 were selected for molecular identification because of distinct colony morphologies. Four loci, actin (ACT), chitin synthase (CHS1), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and the internal transcribed spacer (ITS), were amplified and sequenced using primers ACT-512F/ACT-783R, CHS-79F / CHS-354R, GDF/GDR, and ITS1F/ITS4 (Damm et al. 2019), respectively. The obtained sequences (ACT: PZ529002, PZ529005, PZ528995, PZ528990, PZ528998; CHS1: PZ564980, PZ564983, PZ564973, PZ564968, PZ564976; GAPDH: PZ528983, PZ528986, PZ528976, PZ528971, PZ528979; ITS: PZ484553, PZ484556, PZ484546, PZ484541, PZ484549) shared 100% identity with those of Colletotrichum spp. (ACT:MG600926; CHS1: OM960722; GAPDH: LC797746; ITS: PZ707414). A maximum likelihood tree of concatenated multi-locus sequences placed the strains in the C. plurivorum clade. Pathogenicity was tested on 2-year-old healthy P. notoginseng plants (5 leaves per strain). Sterile needles were used to create 6 micro‑incisions on each leaf, and 15‑day‑cultured mycelium plugs (5‑mm diameter) were inoculated onto the incision sites, while 5‑mm blank plugs served as controls. Plants were maintained at 25 °C with a 12-h photoperiod and 80% RH. After 4 days, inoculated leaves developed symptoms similar to those observed in the field. The strains were re-isolated and confirmed via morphological and molecular analyses, fulfilling Koch’s postulates. The assay was repeated twice with consistent results. C. panacicola and C. gloeosporioides were reported to cause anthracnose on P. notoginseng (Wei et al. 2017). To our knowledge, this is the first report of C. plurivorum causing anthracnose of P. notoginseng in China. This finding provides baseline data for pathogen surveillance and integrated control of anthracnose on P. notoginseng production systems.