First Report of Fusarium Crown and Root Rot Caused by <i>Fusarium solani</i> on St. John's-Wort in Argentina
Bibliographic record
Abstract
Since 2001, 15 to18% of commercial plantings of the medicinal plant St. John's-wort (Hypericum perforatum L.) in Buenos Aires Province, Argentina were affected by a new disease. Disease symptoms of crown and root rot, wilting, chlorosis, and necrosis of the leaves appeared in circular-to-irregular shaped sectors of 12- to 14-month-old plants. Symptoms began with foliage turning yellow followed by an irregular, brown necrosis of the leaf margins. Lesions coalesced to form large necrotic areas causing a severe defoliation of the basal and upper leaves. A soft rot affected the crown and roots causing a complete maceration of these tissues. Infected plants broke off easily because the crown region and the roots were destroyed. As the disease developed, a dark brown discoloration girdled the stems that progressed above the soil line to the apex. The infected stems became dry and breakable. Finally, the affected plants died. Segments (1 cm long) were taken from roots and rotted crowns of diseased plants, dipped in 70% ethanol, surface sterilized with NaOCl (1%) for 1 min, and rinsed in sterile water. Each segment was blotted dry and placed on potato dextrose agar. Plates were incubated in the dark at 26°C for 4 to 7 days. The predominate fungus isolated from the diseased tissue was identified as Fusarium solani (Mart.) Sacc. (1). Koch's postulates were completed by dipping the roots of seedlings in a 2 × 106 conidia per ml suspension of a single spore isolate for 45 min. Plants were repotted (20 inoculated and 10 controls) in a sterilized soil mix (soil/sand 2:1) and held in the greenhouse at 23 to 26°C. Characteristic symptoms identical to the original developed on 90% of inoculated plants within 2 weeks after inoculation. Symptoms included wilt and collapse, crown and root rot, and death of the plants. The fungus was recovered from symptomatic tissues. Control plants dipped into distilled water remained healthy. The experiment was repeated, and the results were identical to the first inoculations. To our knowledge, this is the first report of St. John's-wort as a susceptible host of F. solani. Reference: (1) P. E. Nelson et al. Fusarium species. An Illustrated Manual for Identification. Pennsylvania State University Press, University Park, 1983.
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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 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".