QTL Mapping and Inheritance of Clubroot Resistance Genes Derived From Brassica rapa subsp. rapifera (ECD 02) Reveals Resistance Loci and Distorted Segregation Ratios in Two F2 Populations of Different Crosses
Bibliographic record
Abstract
In this study, Brassica rapa subsp. rapifera (ECD 02) which exhibits broad-spectrum resistance to many Canadian Plasmodiophora brassicae isolates was crossed with two clubroot-susceptible B. rapa accessions and the B. napus cv. ‘Westar’ to produce three F2 populations. The F2 plants were screened against P. brassicae pathotypes 3H, 5X and 5G. The Chi-square goodness of fit test showed that the vast majority (≈ 90%) of the crosses that produced the F2 populations showed segregation ratios of 9R:7S, 5R:11S and 11R:5S. These were modifications of the 15R:1S ratio expected for the inheritance of two dominant major clubroot resistant (CR) genes from ECD 02. The distorted segregation ratios suggest that the two resistance genes are on different chromosomes and that two genes interact in an epistatic manner to confer resistance. Genotyping was conducted with 144 PCR-based markers in two of the three F2 populations. Linkage and QTL analysis with the polymorphic markers identified one and two QTLs on chromosome A03 to be associated with resistance to P. brassicae pathotype 5X and 5G, respectively. The QTLs clustered in genomic regions on the A03 chromosome of B. rapa where the CRa/CRbKato gene(s) are mapped. In addition, the Crr1 gene on the A08 chromosome of B. rapa was detected in the two populations. Therefore, the phenotypic and molecular data confirm the existence two CR genes in ECD 02. This is the first study that shows that major dominant genes in Brassica interact in a non-additive manner to confer resistance to different P. brassicae pathotypes.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".