First Report of <i>Didymella pomorum</i> Causing Leaf Blight on <i>Angelica sinensis</i> in China
Bibliographic record
Abstract
Angelica sinensis (Oliv.) Diels, is a perennial herbaceous plant of the Umbelliferae family. It has a long history of cultivation and is highly valued as a traditional Chinese medicine in China (Zhang et al. 2012). In September 2023, leaf blight on A. sinensis with an average disease incidence of 56% was recorded in an approximately 6.7-ha production field in Lijiang, Yunnan province, China (26.8215°N, 100.2369°E). At first, small, chlorotic lesions appeared on the leaves. They subsequently increased in density and gradually merged, causing leaves to yellow and wither. Ultimately the blight casused death of the entire foliage. In order to identify the causal agent, cross-sectional segments (5×5 mm2) were cut from the edge of leaf lesions, surface disinfected with a 1% sodium hypochlorite solution for 3 min and rinsed three times with sterile distilled water. They were subsequently placed on potato dextrose agar (PDA) plates and incubated for 3 days under a 12-h photoperiod at 28℃. A total of ten isolates with similar morphological characteristics were obtained by single spore isolation. After 10 days of incubation on PDA, the colony morphology of these isolates was characterized by a brownish central area with a white edge. Aged colonies became wrinkled in the center of the colony. Conidia (n = 30) were elliptical and brown, with a size range of 4.11 to 6.55 μm (average 5.37±0.74 μm) × 3.17 to 4.62 μm (average 3.92±0.43 μm). Chlamydospores (n = 30) formed chains in series, spherical or elliptical in shape, ranging from yellow-brown to dark brown, with a size range of 12.30 to 13.70 μm (average 12.98±0.46 μm) × 4.20 to 5.30 μm (average 4.63±0.26 μm). The nuclear ribosomal internal transcribed spacer region (ITS), the second largest subunit of RNA polymerase II (RPB2), and the 28S nuclear ribosomal large subunit rRNA (LSU) region of two isolates were amplified with the primer pairs ITS1/ITS4 (White et al. 1990), fRPB2-5F/fRPB2-7cR (Liu et al. 1999), and LR0R/LR5 (Schoch et al. 2012), respectively. These amplicons were sequenced bidirectionally and assembled. The two isolates produced the same nucleotide sequences, and the sequences of a representative isolate (AsDp1) were deposited in GenBank. BLASTn analyses showed that the ITS (PP510616), RPB2 (PP526010), and LSU (PP550143) sequences of isolate AsDp1 were 100%, 99.66%, and 100% identical with those of Didymella pomorum ex-type isolate CBS 354.52 (MH857081, KT389616, and MH868616), respectively. A phylogenetic tree was constructed based on the ITS, RPB2, and LSU concatenated nucleotide sequences using the maximum likelihood method in MEGAX. Isolate AsDp1 was clustered with four D. pomorum isolates. According to the morphological and nucleotide sequences analyses, isolate AsDp1 was identified as D. pomorum (Chen et al. 2015). To determine pathogenicity, 1-year-old A. sinensis plants (approximately 20 cm tall) grown in 7-liter pots filled with sterilized field soil were sprayed until runoff with a 1×106 conidia/ml suspension of isolate AsDp1 onto the foliage, while control plants were sprayed with sterile water. All plants were cultivated under a 12-h photoperiod at 25℃. The pathogenicity tests were performed in triplicate with ten plants in each treatment. After fifteen days, numerous chlorotic lesions appeared on the leaves of all inoculated plants. The symptoms were similar to those found on naturally infected plants in the field, while the control plants remained asymptomatic. Subsequently, D. pomorum was reisolated from the diseased leaves, and the identity was confirmed based on its ITS sequence and morphological characteristics. D. pomorum causing stem canker on Rosa spp. was reported in Canada (Ilyukhin 2022). To our knowledge, this is the first report of D. pomorum causing leaf blight on A. sinensis in China. This etiological finding will potentially pave the way for the development of control strategies of this disease.
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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) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 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".