Influence of Iron on Cylindrocarpon Root Rot Development on Ginseng
Bibliographic record
Abstract
ABSTRACT Cylindrocarpon root rot, caused by Cylindrocarpon destructans, is an important disease on ginseng (Panax quinquefolius) in Canada. We studied the effects of iron (Fe) on disease severity and pathogen growth. When Hoagland's solution was amended with Fe at 56 and 112 mug/ml compared with 0 mug/ml, disease initiation and final severity on hydroponically maintained ginseng roots was significantly (P<0.0001) enhanced. Under field conditions, wounding of roots with a fine needle followed by application of 0.05% FeNaEDTA to the rhizosphere of treated plants significantly enhanced Cylindrocarpon root rot in 2003 and 2004 compared with unwounded roots with Fe or wounded roots without Fe. Foliar applications of Fe (as FeNaEDTA) to ginseng plants three times during the 2002 and 2003 growing seasons significantly increased Fe levels in root tissues. These roots developed larger lesions following inoculation with C. destructans in vitro. When radioactive Fe ((59)Fe) was applied to the foliage of ginseng plants, it was detected in the secondary phloem and in cortical and epidermal tissues within 1 week. Artificially wounded areas on the roots accumulated more (59)Fe than healthy areas. Diseased tissue also had threefold higher levels of phenolic compounds and Fe compared with adjoining healthy tissues. High-performance liquid chromatography analysis revealed enhanced levels of protocatechuic acid, chlorogenic acid, caffeic acid, ferulic acid, cinnamic acid, phloridizin, and quercetin. Phenolic compounds produced in diseased and wounded tissues sequestered Fe in vitro. The effects of Fe on mycelial growth, conidial germ tube length, and secondary branching of germ tubes of C. destructans were examined in vitro. When grown on Chrome-azurol S medium, Fe also was sequestered by C. destructans through siderophore production, which was visualized as a clearing pigmented zone at the margin of colonies. Mycelial dry weight was significantly increased in glucose/ yeast broth containing Fe at 56 or 112 mug/ml. Conidial germ tube length and secondary branching of hyphae also were enhanced after 8 and 16 h by Fe. Colony growth of C. destructans was not enhanced by Fe, but significantly greater spore production was observed with Fe at 56 and 112 mug/ml compared with no Fe in the medium. Although these levels of Fe had no effect on fungal pectinase enzyme activity, polyphenoloxidase (PPO) activity was significantly (P <0.0001) enhanced. We conclude that Fe enhances Cylindrocarpon root rot through enhanced pathogen growth, sporulation, and PPO enzyme activity. Fe sequestered by phenolic compounds produced in wounded tissues can enhance Fe levels at the site of infection. The pathogen also has the ability to sequester Fe at these sites.
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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) | 0.000 | 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) | 0.001 | 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".