First Report of <i>Didymella pomorum</i> Causing Leaf Blight on <i>Angelica sinensis</i> in China
Notice bibliographique
Résumé
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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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,001 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,001 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,001 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».