First Report of Colletotrichum scovillei Causing Anthracnose on Pepper in Yunnan Province, China

Pepper (Capsicum annuum L.) is an economically vital crop in China, with cultivation exceeding 733,000 hectares annually (Zou et al. 2022). Anthracnose, caused by Colletotrichum spp., severely hinders pepper production, causing up to 50% yield losses in epidemic regions (Dean et al. 2012). It primarily infects leaves and fruits, causing necrosis and premature abscission (Diao et al. 2017). In August 2024, severe anthracnose occurred in pepper fields in Dianwei Village, Tadian Town, Yuxi City, Yunnan province, China. Approximately 90% of peppers exhibited symptoms. Infected fruits displayed circular, black, sunken lesions with distinct concentric rings and dense black microsclerotia; severely affected fruits were entirely necrotic. To identify the causal agent, lesion margins from eight symptomatic fruits were surface-sterilized (75% ethanol, 30 s; 2% NaOCl, 1 min; rinsed thrice in sterile water), dried, and plated on PDA at 26°C. Hyphal tips were subcultured 3-5 times for purity. All eight isolates exhibited identical morphology. Representative isolate TD-CTJ-14 and two others underwent characterization. On PDA, isolates produced white, cottony mycelia with even margins. Colonies turned orange-red or cream-colored with age, exhibiting abundant aerial hyphae. Dark grey to black sclerotia formed, occasionally as concentric rings in the central region. Conidia were unicellular, hyaline, cylindrical to ovoid, measuring 7.25–11.18 μm × 2.75–0.92 μm. Septate hyphae and subglobose, brown appressoria were observed. Morphological characteristics aligned with descriptions of C. scovillei (C. acutatum complex). Genomic DNA was extracted, and the ITS region plus portions of the ACT, TUB2, CHS-1, GAPDH, and HIS3 genes were sequenced with primers ITS1/ITS4, ACT-512F/ACT-783R, T1/Bt2b, CHS-79F/CHS-384R, GDF1/GDR1, and CYLH3F/CYLH3R, respectively (Zhang et al. 2024). BLASTn analysis revealed 100% identity to C. scovillei references (GenBank: ITS, PV819267; ACT, PV902541; TUB2, PV902551; CHS-1, PV902561; GAPDH, PV902571; HIS3, PV902581). A maximum likelihood phylogeny (PhyloSuite, concatenated six-loci alignment) confirmed TD-CTJ-14 as C. scovillei. Pathogenicity was confirmed by inoculating healthy mature pepper fruits (cv. ‘Erjingtiao’, field-prevalent cultivar) via both mycelial plug and conidial suspension (1×10⁶ conidia/mL) onto slight wounds (5-mm-deep prick). Sterile PDA plugs and distilled water served as controls. The experiment was repeated three times with five fruits per treatment. After 5 days at 26°C and >90% RH, characteristic lesions developed on all inoculated fruits; controls remained asymptomatic. The pathogen was re-isolated from lesions and confirmed by morphology and ITS sequencing, fulfilling Koch’s postulates. C. scovillei is a known causal agent of pepper anthracnose globally, including in the USA, Canada, Brazil, and Japan, and has been previously reported in Chinese provinces Sichuan, Guizhou, and Gansu provinces (Caires et al. 2014; Li et al. 2021). However, to our knowledge, this is the first report of C. scovillei causing pepper anthracnose in Yunnan province. Yunnan produces >30% of China’s peppers and leads in cultivation area for Capsicum frutescens (bird's eye chili). This first report of C. scovillei in Yunnan indicates expansion into a key production zone, threatening an industry valued at >¥6 billion (US $840 million) annually. This finding is critical for targeted management.