First Report of Quinoa Downy Mildew Caused by <i>Peronospora variabilis</i> in Republic of Korea
Bibliographic record
Abstract
Quinoa (Chenopodium quinoa Willd.) has become increasingly popular due to its high nutritional value and adaptability to harsh environments. Several field trials have recently been conducted to determine the ability of quinoa cultivars to grow under climate and soil conditions of Republic of Korea. During July 2013, which is the rainy season, plants showing typical symptoms of downy mildew were first observed in an experimental plot in Iksan City, Korea. Infection resulted in small to large, irregular chlorotic areas on the upper leaf surface with a gray mildew developing on the abaxial surface, and often leading to early defoliation. The same symptoms of downy mildew were also found in Pyeongchang County and Imsil County, Korea. A sample from Iksan City was deposited in the Korea University Herbarium (Accession No. KUS-F27388) and used for microscopy and molecular studies. Microscopic examination revealed colorless conidiophores emerging from stomata, straight to slightly curved, 350 to 550 × 10 to 18 μm, and sub-dichotomously branched in 5 to 7 orders. Ultimate branchlets were mostly in pairs, flexuous to curved, 10 to 30 μm long, and had obtuse tips. Conidia were pale brown to olivaceous, broadly ellipsoidal to ellipsoidal, and 25 to 32 × 22 to 25 μm with a length/width ratio of 1.20 to 1.35. These characteristics fit well with Peronospora variabilis, which was previously recorded to be parasitic to C. quinoa and C. album, although P. farinosa f. sp. chenopodii has often been considered a causal agent of downy mildew on quinoa (1). To confirm this morphological identification, amplification and sequencing of the internal transcribed spacer (ITS) region of the rDNA of the Korean specimen were performed using procedures outlined by Choi et al. (1) with oomycete-specific primers DC6 and LR0. The resulting 796-bp sequence was deposited in GenBank (Accession No. KF887493). A comparison with the ITS sequences available in GenBank revealed that it is identical to P. variabilis found on C. album (EF614959, EF614961), and shows only one base pair substitution with another isolates from C. quinoa (EU113305, EU113306). Therefore, the pathogen found in Korea was confirmed to be P. variabilis. Downy mildew is the most damaging disease of quinoa in Argentina, Bolivia, Colombia, Ecuador, and Peru (1). Increasing reports of this disease from India, Canada, the United States, Portugal, and Denmark (2,3,4) have revealed its worldwide occurrence and spread. To our knowledge, this is the first report of a downy mildew on quinoa in Korea (3). It suggests that quinoa downy mildew poses a new and serious threat to production of this crop in Korea. References: (1) Y. J. Choi et al. Mycopathologia 169:403, 2010. (2) S. Danielson et al. Seed Sci. Technol. 32:91, 2004. (3) D. F. Farr and A. Y. Rossman. Fungal Databases. Syst. Mycol. Microbiol. Lab., Online publication, ARS, USDA, Retrieved November 5, 2013. (4) A. L. Testen et al. Plant Dis. 96:146, 2012.
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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".