First Report of Target Spot of Broadleaf Tobacco Caused by <i>Rhizoctonia solani</i> (AG-3) in Connecticut
Notice bibliographique
Résumé
In June 2011, 15 transplant beds of broadleaf cigar wrapper tobacco (Nicotiana tabacum L., cv. C9) plants in Hartford County, Connecticut, were observed with almost every plant diseased. Leaf lesion symptoms ranged from small (2 to 3 mm) water-soaked spots to larger (2 to 3 cm) lesions. Disease was subsequently observed, also at nearly 100% incidence in a 10-hectare field on that farm and at additional broadleaf tobacco farms from two other towns in Hartford County and one town in Tolland County. Lesions exhibited a pattern of concentric rings, necrotic centers and tears in the centers, and margins that often resulted in a shot-hole appearance. Some lesions had chlorotic halos. Rhizoctonia solani Kuhn (Thanatephorus cucumeris A. B. Frank) was isolated from the margins of lesions that had been surface sterilized in 0.5% NaOCl for 30 s and then rinsed in sterile distilled water and placed on the surface of half-strength potato dextrose agar (PDA). Multiple isolations were made and the pathogen was identified on the basis of mycelial characteristics including multinucleate cells, septate hyphae wider than 7 μm, and hyphal branches occurring at approximately right angles, constricted at the base (4). Eight-week-old potted tobacco plants were each inoculated by spraying with a mycelial suspension (1 × 105 CFU) of an isolate of R. solani recovered from tobacco onto leaves, or with water alone (five plants each). The plants were placed in plastic bags in a 24°C growth chamber and misted. After 2 days, the bags were removed and the potted plants placed in trays filled to a depth of 1 cm with water in the growth chamber. After 8 days, the pathogen was reisolated from all inoculated plants exhibiting water-soaked spots as disease symptoms. Leaves inoculated with water or half-strength PDA plugs alone were asymptomatic. DNA was liberated from hyphae of the R. solani isolate by bead beating in STE buffer using 0.15 mm zirconium beads. Two microliters of the eluate was used to amplify the ITS region. Amplified DNA was purified in a Qiagen QIAquick PCR purification kit and submitted to the Yale science hill genomic facility for standard Sanger dideoxy sequencing. The sequence was exactly the same as an isolate from Massachusetts that we sequenced in 2010 (GenBank Accession No. HQ241274). The ITS sequence confirmed our identification of this new isolate as R. solani anastomosis group (AG) 3. This disease has been previously reported on tobacco from South America, South Africa, and the southern United States (1), Canada (3), and Massachusetts (2). Conditions were very conducive for disease because 2011 was a very wet year in Connecticut. To our knowledge, this is the first report of this disease in broadleaf cigar wrapper tobacco in Connecticut. The sequence data suggested that it may have been introduced to Connecticut from Massachusetts. We have found the target spot pathogen distributed across the tobacco producing area of Connecticut. This constitutes a serious threat as there are no systemic fungicides currently registered for control of this disease in broadleaf tobacco. References: (1) J. S. Johnk et al. Phytopathology 83:854, 1993. (2) J. A. LaMondia and C. R. Vossbrinck, Plant Dis. 95:496, 2010. (3) R. D. Reeleder et al., Plant Dis., 80:712. (4) B. Sneh et al. Identification of Rhizoctonia species. The American Phytopathological Society, St. Paul, MN, 1991.
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 | 0,001 | 0,000 |
| Communication savante | 0,001 | 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 ».