Host range and genetic characterization of the stem and bulb nematode, «Ditylenchus dipsaci», from Eastern Canada
Bibliographic record
Abstract
The stem and bulb nematode, Ditylenchus dipsaci, is a plant-parasitic nematode responsible for major economic loss worldwide. A wide host range, reaching more than 500 plants species and the presence of more than 30 biological races defined by their host preference, make this species one of the most difficult nematodes to manage. Since 2011, garlic producers from Ontario and Quebec have been particularly affected with economic losses caused by this pest. An appropriate extraction method is essential for the detection of the nematode. However, the extraction efficacy will be influenced by many factors such as the nematode species (size and motility), the material to be diagnosed (soil or plants tissues) and the type of soil or plants tissues. Therefore, many different methods exist, each with their own advantages and disadvantages. Three extraction methods (Baermann pan, Baermann funnel and sonication) were compared for the extraction of nematodes from garlic bulbs, stems and leaves. Three methods (Baermann pan, Baermann funnel andsugar flotation) were also tested on four types of soil sample. This study confirmed the efficiency of the Baermann pan with D. dipsaci, both with soil and plant tissue samples. Reproduction of D. dipsaci on a particular host depends on its biological race, which was unknown for the populations of eastern Canada. In this study, the host range of four populations of D. dipsaci from Quebec and Ontario was determined in a greenhouse test on 11 crops. Garlic, onion and green onion showed great susceptibility to the nematode while reproduction on potato was poor. No development was observed on corn, soybean, barley, alfalfa, mustard, carrot, and lettuce. These plants could therefore be used in rotation crops in a control program. Finally, thirty-two populations of D. dipsaci were genetically characterized using genotyping-by-sequencing. Comparison of allele frequencies at 481 SNPs showed that most of the populations had a genotype similar to a reference population from northern Ontario. However, a sample from eastern Quebec exhibited a very distinct genotype and will require further phenotyping in the greenhouse to preclude the possibility of a different race.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.002 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 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".