First Report of Root Rot of Field Pea Caused by <i>Aphanomyces euteiches</i> in Alberta, Canada
Notice bibliographique
Résumé
In recent years, root rots have severely impacted yields of field pea (Pisum sativum L.) in the Canadian province of Alberta. Above-normal precipitation levels in the springs of 2011 to 2013 led to the hypothesis that Aphanomyces euteiches Drechsler may play a role in root rot in water-saturated pea fields. To determine causal agent(s) of root rot, 145 pea fields were surveyed at flowering in July 2013 (1). Symptoms of root rot were abundant; the most prominent included red vascular streaking and dark brown rot of the tap root, indicative of Fusarium spp., but brown discoloration and cortical decay of lateral roots, indicative of A. euteiches, was also observed. Total genomic DNA was extracted from diseased root samples from each field, using the Qiagen DNeasy Plant kit, and amplified with species-specific primers for A. euteiches (2). Fusarium spp. were present in all fields, but seven fields located within a 200-km radius yielded a positive reaction for A. euteiches. Five fields were re-visited in May 2014 to collect soil for a bait test (3). Tests were performed using surface-sterilized pea seeds (cv. CDC Meadow) treated with Allegiance FL (Bayer, a.i. metalaxyl) at a rate of 110 ml/kg of seed. Five seeds per pot were planted into field soils in 10-cm pots with 12 replicate pots per field. Soils were irrigated as needed until the second-node stage and then kept at saturation for 14 days. Thirty day-old pea roots were evaluated for root rot symptoms; plated onto cornmeal agar amended with metalaxyl, benomyl, and vancomycin (MBV) without surface sterilization; and visualized microscopically for presence of oospores in the roots. Roots from three out of the five field soils showed symptoms typical of A. euteiches infection, including honey-brown discoloration, degradation of the root cortex, and presence of oospores. Root rot symptoms from the remaining fields were characteristic of Fusarium root rot, and oospores were not observed in roots. Fungal cultures with fast-growing, white, aerial mycelia characteristic of A. euteiches on MBV, were recovered from roots with Aphanomyces root rot symptoms, and transferred to PDA. To confirm pathogen identity, total DNA was extracted from 7-day-old cultures growing on PDA using the Qiagen DNeasy Plant Kit. The ribosomal DNA internal transcribed spacer (ITS) region was amplified using the primer pair ITS1 and ITS4 and sequenced (4). The sequences, deposited in GenBank with accession numbers KM486065, KM486066, and KM486067, were 100% identical to the ITS rDNA sequence of several isolates of A. euteiches using a BLASTn query. Fusarium spp. were also recovered from all root samples in the soil bait test. Total DNA extracted from roots was used in PCR assays with A. euteiches-specific primers as described above. PCR amplification of root DNA was successful only from the same three fields that showed Aphanomcyces root rot symptoms, further verifying presence of A. euteiches. The inability to detect or recover A. euteiches from two fields that had tested positive in the survey was likely due to patchy distribution of this pathogen and emphasizes the importance of rigorous soil collection methods to accurately detect pathogens. Although this is the first record of A. euteiches on field pea in Alberta, the distribution of A. euteiches within a 200-km radius in southern Alberta indicates that it has likely been present in soils for several years. The interaction between A. euteiches and Fusarium spp. infection in the root rot complex of field pea and their impact on field pea production in Alberta is currently being investigated. References: (1) S. Chatterton et al. Can. Plant Dis. Surv. 94:189, 2014. (2) C. Gangneux et al. Phytopathology 104:1138, 2014. (3) D. Malvick et al. Plant Dis. 78:361, 1994. (4) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.
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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) | 0,000 | 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 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 ».