First Report of Clover Yellow Edge Phytoplasma in <i>Corylus</i> (Hazelnut)
Notice bibliographique
Résumé
During investigations into the cause of a stunt syndrome affecting cultivated European hazelnut trees (Corylus avellana L.) in Oregon, the clover yellow edge (CYE) phytoplasma was detected for the first time in this crop. The cause of hazelnut stunt syndrome (HSS) is unknown, but the disease has been transmitted by grafting and apparently has moved within orchards through root grafts (1). Severely affected trees persist for many years, but their nut production is greatly reduced. Previous attempts to detect viruses, bacteria, and other pathogens have been unsuccessful. HSS has been observed only in Oregon and already had been present for more than 10 years when it was first reported in 1970 (1). In June, 1999, leaf samples were collected from two affected and two apparently healthy (symptomless) hazelnut trees in a field plot at Oregon State University, Corvallis, and from a healthy greenhouse-grown tree. Leaf samples were sent to the USDA Beltsville, MD, laboratory, where they were assessed for phytoplasma infection, using nested polymerase chain reactions (PCRs). PCRs were primed by phytoplasma universal primer pairs P1/P7 and F2n/R2 (3) for amplification of phytoplasma 16S ribosomal (r) DNA (16S rRNA gene) sequences according to the procedures of Gunderson and Lee (2). Phytoplasma-characteristic 1.2-kbp DNA sequences were amplified from all field-tree samples. No DNA sequences were amplified from samples of the greenhouse-grown tree. Restriction fragment length polymorphism patterns of rDNA digested with AluI, KpnI, HhaI, HaeIII, HpaII, MseI, RsaI, and Sau3A1 endonucleases indicated that all diseased hazelnut trees as well as symptomless field trees were infected by a phytoplasma classified in group 16SrIII (peach X-disease group), subgroup B (III-B, type strain CYE phytoplasma). No phytoplasmas were detected in samples from the greenhouse-grown tree. Nucleotide sequences were determined for 16Sr DNA fragments amplified from the hazelnut CYE phytoplasma in nested PCRs primed with F2n/R2. The sequences were deposited in GenBank under Accession no. AF189288. Sequence similarity between 16Sr DNAs of the hazelnut CYE strain (CYE-Or) and the Canadian clover yellow edge strain (CYE-C, GenBank Accession no. AF175304) phytoplasma was 99.9%. Decline and yellows disorders of hazelnut in Germany and Italy have been associated with infections by apple proliferation, pear decline, and European stone fruit yellows phytoplasmas (4). These phytoplasmas are classified in 16Sr group X, the apple proliferation group of phytoplasmas. This is the first report of the CYE phytoplasma infecting Corylus. References: (1) H. R. Cameron. Plant Dis. Rep. 54:69, 1970. (2) D. E. Gunderson and I.-M. Lee. Phytopathol. Mediterr. 35:144, 1996. (3) R. Jomantiene et al. HortScience 33:1069, 1998. (4) C. Marcone et al. Plant Pathol. 45:857,1996.
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| 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) | 0,002 | 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 tête enseignante, 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 ».