First Report of Blackleg Disease Caused by <i>Leptosphaeria maculans</i> on Canola in Brazil
Bibliographic record
Abstract
Canola (Brassica napus L.) is a relatively new crop in Brazil, having been grown there for approximately 8 years. In 2000, leaf lesions and stem cankers were observed in cvs. Hyola 420 and Hyola 401 in farmers' fields in the state of Rio Grande do Sul. Cankered stems were received at the University of Manitoba, Canada, from Rio Grande do Sul for disease identification. Small pieces of the stem were cut from the cankered area, and standard protocol was followed to surface sterilize the stem pieces. Stem pieces were plated on V8 agar medium and incubated under light for 12 days. Typical fungal colonies with concentric rings containing pycnidia formed on the V8 agar. The colony characteristics were typical of the blackleg pathogen, Leptosphaeria maculans (Desmaz.) Ces. & De Not. (anamorph = Phoma lingam) (Tode:Fr.) Desmaz.). Blackleg is an economically important and serious disease in many parts of the world including Australia, Canada, the United States, and Europe. L. maculans strains can be characterized in four pathogenicity groups (PG1 through PG4) based on differential testing procedures giving interaction phenotype (IP) reactions (2). Two weeks after plating on V8 media, plates were flooded with sterile distilled water, and pycnidiospores were harvested. Flats of multipots filled with Metro Mix were seeded with three cultivars (Westar, Glacier, and Quinta). One-week-old cotyledons from the three cultivars were inoculated with pycnidiospore suspensions (2 × 10 7 pycnidiospores per ml) of seven Brazilian isolates, numbered 7, 8, 9, 11, 15, 16, and 18, respectively. Each cotyledon leaf, punctured in the center with a needle, was inoculated with a 10-μl droplet of the inoculum. Disease evaluations were made 11 days after inoculation using a 0 to 9 rating scale (1). This screening was repeated three times from February 2001 to October 2001. After the second repeat, the isolates from Rio Grande do Sul were passed through the highly susceptible canola cv. Westar. Results from all four trials were consistent, and yielded one PG1 isolate (No. 7) and six PG3 isolates. PG1 is classified as a nonaggressive strain, whereas PG3 isolates are classified as aggressive. PG3 isolates would have an IP reaction of 7 to 9, 7 to 9, and 3 to 6 on cvs. Westar, Glacier, and Quinta, respectively. PG2 is the most commonly found aggressive strain in the Canadian prairies. PG3 is predominantly found in Australia, the United Kingdom, and the United States. To our knowledge, this is the first report of blackleg disease caused by L. maculans on canola in Brazil. Differential testing fulfilled Koch's postulates and determined the PG groups found in Brazil (PG1 and PG3). References: (1) P. A. Delwiche. Genetic aspects of blackleg (Leptosphaeria maculans) resistance in rapeseed (Brassica napus) Ph.D. thesis. University of Wisconsin-Madison, 1980. (2) A. Mengistu et al. Plant Dis. 75:1279, 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".