First Report of Bronze Leaf Disease on Hybrid Poplar (<i>Populus</i> × <i>canescens</i> ‘Tower’) Caused by <i>Apioplagiostoma populi</i> in Manitoba, Canada
Bibliographic record
Abstract
Poplars (Populus alba × P. tremula (P. × canescens) (Aiton) Smith cv. Tower) are common ornamental and windbreak trees in Manitoba and across the Canadian prairie provinces because of their rapid growth and columnar growth habit. Bronze leaf disease symptoms have been reported on five poplar species (P. alba, P. canescens, P. grandidentata, P. tremula, and P. tremuloides) (2), and the disease presents a significant barrier to the development and continued use of poplars (1). Elimination of tower poplars would represent a significant loss to the Canadian horticultural industry, and the costs incurred in the replacement of existing windbreaks would be high. In August 2002, we observed symptoms of bronze leaf disease on approximately 20-year-old tower poplars, ranging in height from 8 to 12 m at a tree nursery and golf course near Carman, Manitoba (49°30'N, 98°0'W). The leaf laminae of affected plants were chocolate brown, and the petioles and veins were yellow to light green. In the nursery windbreak, 70 trees had foliar symptoms on 30 to 80% of the canopy. At the golf course, eight trees had foliar symptoms on approximately 5 to 20% of the canopy. No fruiting structures were visible on leaf or shoot tissue, and no staining of vascular tissues was observed. Attempts to isolate the causal fungus of bronze leaf disease on artificial media have been unsuccessful (2). In October 2002, branches with symptomatic leaves were covered with netting, and the trapped leaves were left to overwinter. In March 2003, symptomatic leaves were brought to the laboratory and surface sterilized in 1% NaOCl for 1 min, rinsed with sterile water, and incubated at 18°C in moist chambers. After 2 weeks, dark brown, beaked, single perithecia that were 150 to 200 μm long × 150 μm wide emerged from the upper and lower leaf surfaces. Asci were fusoid clavate with a conspicuous apical ring and contained 4 or 6 spores. The two-celled, hyaline ascospores varied from 10.5 to 14.5 × 2 to 3 μm, the basal cell shorter than the apical cell. Leaf symptoms and microscopic fungal features matched those of Apioplagiostoma populi (Cash & A.M. Waterman) Barr, the cause of bronze leaf disease (1,2). Voucher specimens have been deposited in the U.S. National Fungus Collections (BPI 843385). To our knowledge, this is the first report of this fungus in western Canada, and the first confirmed report of this pathogen on tower poplar in Canada. References: (1) E. K. Cash and A. M. Waterman. Mycologia 49:756, 1957. (2) J. A. Smith et al. Plant Dis. 86:462, 2002.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".