Leaf Spot Caused by <i>Irpex lacteus</i> on Tobacco in China
Notice bibliographique
Résumé
Tobacco (Nicotiana tabacum L.) is an important commercial crop in China. In June 2023, disease symptoms were seen in a commercial tobacco field in Bijie City (27.09° N, 105.36° E), Guizhou province, China. Typical symptoms first appeared on the lower leaves as round brown spots, with a light center and a faint yellow small halo. Approximately 25% of the plants were symptomatic in a 3.5-ha field. From 8 plants, 16 small pieces of leaf tissue (6 × 6 mm) were cut from the edge of the lesions, including live and dead portions. These were surface sterilized in 1% hypochlorite for 30 s, and then placed on potato dextrose agar (PDA) amended with kanamycin (0.1 mg/ml). After 48 hours at 28 °C, 12 fungal strains were recovered. Eight strains presented a consistent morphology, while the remaining four strains varied in morphology. All 12 strains were tested for pathogenicity on detached leaves and only the eight (presenting a consistent morphology) showed disease. The other four strains showed no disease. A representative isolate, MDY, was selected for causal agent identification. The hyphae were white, slightly raised, thin-walled, straight, and 2.0-4.0 μm in diameter. There was no detectable odor. Conidia were numerous, clustered, ovoid, colorless, and 5-8 µm x 4-5 µm. These characteristics were similar to those reported for Irpex lacteus (Chi et al. 2002). The internal transcribed spacer (ITS), large ribosomal subunit (LSU) and small ribosomal subunit (SSU) loci of isolate MDY were, respectively, amplified with primers ITS1/ITS4, LR5/LROR, and NS1/NS4 (Schoch et al. 1998; Melnikov et al. 2012), and sequenced using both forward and reverse primers. Consensus sequences from each pair of primers were used in BLAST against the NCBI GenBank database. The ITS sequence (OR366346) showed 99.9% identity (648/649 bp) with I. lacteus (MH890689), the LSU sequence (OR878461) showed 99.6% identity (904/908 bp) with I. lacteus (MH867969), and the SSU sequence (OR878462) showed 99.5% identity (969/974 bp) with I. lacteus (MF190370). Neighbor-Joining analysis was carried out using the ITS sequence of MDY, several related sequences from GenBank, and Macrocybe gigantea OQ644634 as outgroup. MDY clustered with other I. lacteus sequences with 95% bootstrap support. Morphological and molecular results supported this isolate as I. lacteus. Pathogenicity was tested on six tobacco seedlings (cv. Yunyan 87) at the six-leaf stage using hyphal plugs from isolate MDY on non-wounded attached leaves, while controls received PDA plugs. This test involving three treated plants and three control plants was repeated three times. All tobacco seedlings were kept in a growth chamber at 25 ± 5 °C and 85% relative humidity. After 7 days, leaf spots similar to field symptoms were observed on the treated leaves, while no symptoms were observed on control leaves. Koch's postulates were fulfilled by re-isolation of the pathogen from the diseased leaves, confirmed by ITS sequencing. From previous work, I. lacteus was described and reported as an endophyte in tobacco in Enshi, Hubei (Yuan et al. 2018), and some endophytes are known to be latent pathogens (Brown et al. 1998), but to the best of our knowledge, this is the first report of I. lacteus causing tobacco leaf spots. Due to potential serious damage caused by this disease on tobacco in China, further research is needed to establish its incidence in tobacco fields and the source of the inoculum in localized infections.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
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) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 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) | 0,000 | 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 ».