First Report of <i>Colletotrichum coccodes</i> Causing Leaf and Neck Anthracnose on Onions (<i>Allium cepa</i>) in Michigan and the United States
Bibliographic record
Abstract
In July of 2010, dry, oval lesions, each with a salmon-colored center and bleached overall appearance, were observed on the leaves and neck of onions plants growing in production fields of Newaygo, Ottawa, Kent, and Ionia counties, Michigan. Acervuli and setae that are characteristic of Colletotrichum spp. were observed with a dissecting microscope, and elliptical conidia (8 to 23 × 3 to 12 μm) with attenuated ends were observed with a compound microscope. Symptomatic tissues were excised and cultured onto potato dextrose agar amended with 30 and 100 ppm of rifampicin and ampicillin, respectively. The cultures produced pale salmon-colored sporulation after growing for 5 days at 22 ± 2°C and black microsclerotia after 2 weeks. Six isolates were confirmed as C. coccodes based on sequence analysis of the internal transcribed (ITS) region of the ribosomal DNA and a 1-kb intron of the glutamine synthase gene (GS) (2). Sequences were submitted to GenBank (Accession Nos. JQ682644 and JQ682645 for ITS and GS, respectively). Pathogenicity tests were conducted on two- to three-leaved ‘Stanley’ and ‘Cortland’ onion seedlings. Prior to inoculation, seedlings were enclosed in clear plastic bags overnight to provide high relative humidity. The bags were removed, and seedlings were sprayed inoculated with a C. coccodes conidial suspension (5 × 10 5 conidia/ml and 25 ml/plant) in sterile double-distilled water. Control seedlings were sprayed with sterile double-distilled water. Tween (0.01%) was added to the conidial suspension and the water. Plants were enclosed in bags for 72 h postinoculation and incubated in growth chambers at 28°C day/23°C night with a 12-h photoperiod. Sunken, oval lesions were observed on the foliage of the onion seedlings inoculated with C. coccodes 4 days postinoculation. Lesions coalesced and foliage collapsed 7 days postinoculation. Control plants remained asymptomatic. When five leaf samples per replication were detached and incubated in a moist chamber for 3 days at 21 ± 2°C, abundant acervuli and setae were observed on the symptomatic tissue but not on control tissue. C. coccodes was consistently recovered from the onion seedling lesions. Six different Colletotrichum spp. have been reported to cause diseases on onions worldwide (1,4). C. circinans, which causes smudge, is an occasional onion pathogen in Michigan, while C. gloeosporioides has only been reported to be infecting onions in Georgia (3). To our knowledge, this is the first report of C. coccodes infecting and causing disease in onions plants. References: (1) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , August 6, 2010. (2) J. C. Guerber et al. Mycologia 95:872. 2003. (3) C. Nischwitz et al. Plant Dis. 92:974. 2008. (4) H. F. Schwartz, and K. S. Mohan. Compendium of Onion and Garlic Diseases and Pests, 2nd ed. The American Phytopathological Society, St. Paul, MN. 1995.
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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".