First Report of Halo Blight of Hop (<i>Humulus lupulus</i>) Caused by <i>Diaporthe humulicola</i> in Quebec, Canada
Bibliographic record
Abstract
Halo blight of hop caused by Diaporthe humulicola has recently been reported in Michigan and Connecticut (Higgins et al. 2021, Allan-Perkins et al 2020). In August 2020 growers in Quebec, Canada reported necrotic foliar lesions and desiccation of the hop strobile (cone) on Chinook and Nugget cultivars. The foliar lesions were dry concentric circles with a chlorotic halo surrounding the lesions; no pycnidia were observed on leaves or cones. Up to 100% of the infected bract tissue was dry and easily shattered, the grower estimated that more than 90% of the plants in the hopyard exhibited symptoms. Twenty-six isolates were obtained from surface-sterilized leaf and cone tissue by plating the leading edge of lesions on potato dextrose agar. Fungal isolates were hyphal tipped and were incubated at 22°C with a 12 h photoperiod. After 21-days, all cultures were white to beige with pycnidia. DNA was extracted from cultures using the MagMAX Plant DNA Isolation Kit (Applied Biosystems, Foster City, CA). DNA amplification of a representative isolate (CD6C) was performed with primers ITS1/ITS4 (White et al. 1990) for the internal transcribed spacer (ITS), CYLH3F/H3-1b (Glass and Donaldson 1995) for histone 3 (HIS), and Ef1728f/EF1-986R (Carbone and Kohn 1999) for translation elongation factor 1-α (TEF). Amplification primers were used for bidirectional Sanger sequencing, reads were assembled using Geneious Prime (Biomatters, New Zealand), and identified using NCBI BLAST. BLAST results showed that the sequences for TEF, ITS, and HIS all had 100% pairwise identity to Diaporthe sp. 1-MI (MT909101, MT909099, MT909093, OK001342, MZ934713, OK001341). Futhermore, BLAST results showed that ITS and HIS have 100% pairwise identity D. humulicola (MN152929, MN180214). The TEF sequence also had 99.7% pairwise identity to D. humulicola (MN180209). Koch's postulates were conducted by inoculating six 3-mo-old 'Chinook' plants with conidia harvested from 28-day-old cultures and spraying 50 ml of inoculum (6 x 105 conidia/ml) or water to each plant. Plants were then stored in a greenhouse at 100% relative humidity at 22°C with a 14-h photo period. Lesions appeared on the adaxial side of the leaf after 21 days. D. humulicola was re-isolated from all infected leaf tissue, but not from any water inoculated plants and identified by conidial morphology using descriptions from Higgins et al. (2021). So far, Diaporthe sp. 1-MI appears to be synonymous with Diaporthe humulicola, but currently two names are being utilized (i.e. Diaporthe leaf spot and halo blight). In Higgins et al., (2021) it was proposed that the name halo blight might be more appropriate because disease symptoms are not confined to the leaves and cause significant blighting of cones. Halo blight caused by D. humulicola appears widespread in Michigan and Canada and may become an issue in other eastern North American growing regions with humid conditions.
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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".