First report of bacterial spot (<i>Xanthomonas cucurbitae</i>) of pumpkin in Ontario, Canada
Notice bibliographique
Résumé
In August 2012, leaves of pumpkin (Cucurbita pepo cvs. Gladiator, Aladdin, Apollo, and Super Hero) in Kent County, Ontario, Canada were observed with 1-4 mm irregular-shaped light brown to tan lesions, often with a chlorotic halo. Mature fruit had 2-4 mm light brown to tan sunken lesions with dark borders (Fig. 1), and later developed severe soft rot. Approximately 35 ha were affected with more than 50% of foliage and 60% of fruit damaged. Isolations were made from fruit using the method described by Cuppels et al. (1) but with tryptic soy agar. More than 95% of colonies isolated were opaque, light to bright yellow, glistening, circular, and flat. Isolates were gram-negative. Substrate utilisation profiles (Biolog, Hayward, CA) of Ontario isolates CT12PT1A and CT12PT3 were compared with those described for Xanthomonas DNA homology groups (Vauterin et al. 4). Utilisation patterns of the 95 substrates in the BIOLOG assay for CT12PT3 and CT12PT1A had 96.8% and 94.7% identity with members of Group 8 (X. cucurbitae), and both had 95.8% identity with at least one of the three X. cucurbitae isolates reported by Dutta et al. (2) (Dutta, pers. communication). The 16S DNA sequences of CT12PT3 and CT12PT1A were obtained with primers designed by the Pest Diagnostic Clinic, University of Guelph (5'GCYTAACACATGCAAGTCGA-3' and 5'-GTGTGTACAAGNCCCGGGAA-3'). A BLAST search of the GenBank database revealed that both sequences (GenBank Accession Nos. KJ817203 and KJ817204) had 100% nt identity to the 16S DNA sequences of Xanthomonas dyei (NR_104949), Xanthomonas pisi (AB680442), Xanthononas vesicatoria (AY288080 and AF123088) and Xanthononas cucurbitae (AB680438). In addition, 928 bp of the gyrase subunit B gene (gyrB) was sequenced with primers gyrB-F and gyrB-R (Hamza et al., 3). Both Ontario isolates (KJ817205 and KJ817206) had 100% nt identity with gyrB of X. cucurbitae (HM569161.1 and HM569162.1). The next closest matches were Xanthomonas axonopodis pv. citrumelo (CP002914.1) and Xanthomonas campestris pv. raphani (CP002789.1), with 94% nt identity. A neighbour-joining tree from a ClustalW multiple sequence alignment of the overlapping regions of these gyrB sequences and 14 other Xanthomonas species showed that sequences from both Ontario isolates clustered only with HM569161 and HM569162 with high bootstrapping values (Fig. 2). These results strongly suggest the isolates are X. cucurbitae. To confirm pathogenicity of the isolates, a bacterial suspension (1 times 107 cfu/ml) of each isolate was applied to the leaves of four pumpkin plants (cv. Howden) using a hand-held mist sprayer. Plants were covered for 24h under a translucent plastic box and maintained under artificial light with 16h day length at 24-28°C. Small lesions with slight chlorotic haloes were observed on all inoculated plants 10 days post inoculation (Fig. 3). No symptoms were observed in the water control. Bacteria were isolated from lesions as previously described. The gyrB sequences of these isolates had 100% nt identity to the original isolates, and the BIOLOG substrate utilisation tests showed 100% and 98.9% similarity to CT12PT3 and CT12PT1A respectively. The presence of bacterial spot caused by X. cucurbitae poses a new threat to pumpkin and squash production in Ontario.
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) | 0,001 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,003 | 0,001 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,001 | 0,001 |
| Intégrité de la recherche | 0,000 | 0,001 |
| 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 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 ».