First Report of Halo Blight on Hop (<i>Humulus lupulus</i>) Caused by <i>Diaporthe humulicola</i> in Minnesota
Bibliographic record
Abstract
Halo blight, caused by Diaporthe humulicola, is an emerging issue in hop production in the Upper Midwestern and Eastern North America. Reports of halo blight thus far have included Connecticut, Michigan, New York, and Quebec (Allan-Perkins et al.; Hatlen et al. 2022; Higgins et al. 2021; Sharma et al. 2022). In August 2020, brownish-gray necrotic foliar lesions and damaged cones were observed in an experimental hopyard consisting of a breeding population of hop plants grown at the University of Minnesota - Southern Research and Outreach Center in Waseca, MN. The foliar lesions consisted of necrotic concentric circles with some possessing chlorotic halos. Damage to the cones often appeared as reddish brown as bands around cone midsections, scattered on bracts and bracteoles, and in severe cases near entire cones. Disease incidence within the experimental hopyard was observed on >50% of hop plants. No pycnidia were observed on leaves or cones following collection of samples. A total of eleven samples were obtained from diseased leaves or cones. Symptomatic plant tissue was surface-sterilized and sections excised from the leading edge of lesions were plated onto potato dextrose agar (PDA). Fungal growth was hyphal tipped and incubated at 22° C under a 12-h photoperiod for a period of 21 days (Hatlen et al 2022). Culture characteristics on PDA included raised white to light gray mycelium with irregular pycnidia distribution over the surface. DNA was extracted from mycelia using the MagMAX Plant DNA Isolation Kit (Applied Biosystems, Foster City, CA). A representative isolate (M4N) was selected for DNA amplification and bi-directional Sanger sequencing using the following primers ITS1/ITS4 (ITS) for the internal transcribed spacer, CYLH3F/H3-1b for histone 3 (HIS), and Ef1728f/EF1-986R for translation elongation factor 1-α (TEF) (Carbone and Kohn 1999; Glass and Donaldson 1995; White et al. 1990). Following amplification and sequencing, reads were trimmed and assembled using Geneious Prime (Biomatters, New Zealand). BLASTn analysis revealed that the ITS (GenBank Accession OQ144379), HIS (GenBank Accession OQ256246), and TEF (GenBank Accession OQ256245) were 99 - 100% identical to D. humulicola sequences (MN152927, MN180213, MN180207) infecting hop in other US regions (Allan-Perkins et al. 2019; Hatlen et al. 2022). To complete Koch's postulates, two sets each of six 3-month old plants of the hop cv. 'Chinook' were inoculated with either 50 mL of conidial suspension (6 x 105 conidia/mL) derived from pycnidia harvested from 28-day old cultures or with water as a negative control. Following inoculation, plants were then grown in a greenhouse at 100% relative humidity at 22°C with a 14-h photoperiod. Light brown lesions with concentric circles appeared on the adaxial side of the leaf after 3 weeks but were not observed on mock-inoculated plants. We subsequently re-isolated D. humulicola from 100% of infected leaves which was identified based upon colony and conidial morphology using descriptions from Higgins et al. (2021). alpha-conidia (n = 20) averaged 10.96 µm ± 1.12 in length and 5.11 µm ± 0.67 in width, were unicellular and hyaline. No beta-conidia were observed, consistent with previous reports of this pathogen. No disease symptoms appeared on mock-inoculated plants, and D. humulicola was not recovered from mock-inoculated plants. There is significant concern regarding the increasing prevalence of D. humulicola as an emerging pathogen affecting hop production across the Midwestern and Great Lakes region of North America. Future research is needed to determine differences in hop varietal susceptibility and fungicide efficacy for management of this disease.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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".