First Report of Damping-Off of Canola Caused by <i>Rhizoctonia solani</i> AG 2-1 in Washington State
Bibliographic record
Abstract
In early September 2003, winter canola (Brassica napus L) cv. Inca was direct seeded into plots previously cropped with spring barley at the Washington State University Dryland Research Station at Lind, WA. Before planting, the plots received 80 mm of water by sprinkler irrigation, and 2 weeks later, volunteer barley was killed with Paraquat contact herbicide. In late September, 3 weeks after planting, canola seedlings exhibited postemergence damping-off and lesions on the hypocotyls, resulting in significant stand reductions. Rhizoctonia solani was isolated from infected hypocotyls using water agar amended with chloramphenicol (100 μg/ml). Cultures on potato dextrose agar produced dark brown colonies with dark brown microsclerotia. Three isolates were grown on autoclaved oat seed for 3 weeks in 1-liter Erlenmeyer flasks at 22°C, and colonized seed was air dried in a laminar flow hood, ground in a coffee grinder, and added to a Thatuna silt loam at 1% (w/w). The infested soil was placed into 4- × 20.5-cm plastic tubes and planted with five canola seeds per tube, five tubes per isolate. In the control treatment, soil was not infested. Plants were grown in a temperature-controlled room in a greenhouse at 16°C, 12-h light/dark. Isolates caused pre- and postemergence damping-off after 1 week, and the surviving seedlings had significantly less plant height and dry weight. Isolates were identified as AG 2-1 by pairing cultures with AG 8, 2-1, and 10 on agar-coated slides (1). Selected isolates were also identified as AG 2-1 by sequencing of the ITS 1 and 2 regions of the rDNA and matching them to sequences in GenBank. On a farm north of Pullman, WA in 2004, R. solani was isolated from soil in spring and winter wheat fields using a toothpick baiting method (2). R. solani was found primarily from sites previously cropped with winter and spring canola. These isolates were identified as AG 2-1 and five isolates were tested in the greenhouse, as described above, on canola (cv. Inca), lentil (Lens culinaris Medik. cv. Merrit), wheat (Triticum aestivum L. cv. Madsen), barley (Hordeum vulgare L. cv. Baronesse), pea (Pisum sativum L. cv. Stirling), and chickpea (Cicer arietinum L. cv. Sierra). Three of five isolates significantly reduced emergence of canola, and all isolates significantly reduced dry weight of canola seedlings and caused lesions on hypocotyls. None of the isolates reduced emergence of the other crops. All isolates reduced the dry weight of pea and three isolates reduced plant height. None of the isolates reduced the dry weight of lentil, chickpea, wheat, or barley. One of the isolates was also tested on Arabidopsis thaliana and found to be pathogenic. R. solani AG 2-1 has been reported as an important pathogen on canola in Canada and Australia, but has not been reported from the Pacific Northwest of the United States. R. solani AG 2-1 is also pathogenic on rapeseed, mustard, and subterranean clover and has been isolated from wheat, sugar beets, and potato (3). Canola is a minor rotation crop in cereal-based cropping systems in eastern Washington (1,600 ha in 2005), but there is increasing interest in this oilseed crop for biodiesel production. However, R. solani AG 2-1 may reduce stands and yield of canola. References: (1) W. C. Kronland and M. E. Stanghellini. Phytopathology 78:820, 1988. (2) T. C. Paulitz and K. L. Schroeder. Plant Dis.89:767, 2005. (3) B. Sneh et al. Identification of Rhizoctonia species. The American Phytopathological Society. St. Paul, MN, 1991.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".