First Report of <i>Colletotrichum scovillei</i> Causing Anthracnose on Pepper in Yunnan Province, China
Bibliographic record
Abstract
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.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".