Development of PCR-Based Assays for Detecting <i>Xanthomonas campestris</i> pv. <i>carotae</i>, the Carrot Bacterial Leaf Blight Pathogen, from Different Substrates
Why this work is in the frame
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Bibliographic record
Abstract
Detection of the carrot bacterial leaf blight pathogen, Xanthomonas campestris pv. carotae, was achieved using polymerase chain reaction (PCR) along with primer pairs developed from sequences of cloned random amplified polymorphic DNA (RAPD) fragments. Primer pairs 3S and 9B directed the amplification of ∼350-bp and ∼900-bp (or ∼2 kb) DNA fragments, respectively, from genomic DNA of all known X. campestris pv. carotae strains tested, but not from that of 13 other X. campestris pathovars or other bacterial species, including yellow non-xanthomonad bacteria isolated from carrot tissues and seeds. In tests conducted with an extensive collection of X. campestris pv. carotae-like strains isolated from different substrates from California, Idaho, Oregon, Washington, and Canada, the 3S primer pair directed the amplification of the ∼350-bp target fragment from all strains. These results indicated that the 3S primer pair is highly specific for X. campestris pv. carotae detection. Using the 3S primer pair, PCR assays were developed for detection of X. campestris pv. carotae from colonies on agar media, carrot leaf and stem tissues, and seeds. These tests could be performed in a single day. The PCR-based seed assay detected X. campestris pv. carotae from lots with contamination rates ranging from 2 × 10 2 to 2.3 × 10 8 CFU per gram of seed. This assay gave results similar to a seed-wash dilution plating assay and proved more sensitive than an enzyme-linked immunosorbent assay (ELISA)-based assay.
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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 | 0.001 | 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 it