Cytogenetic Map of Pummelo and Chromosome Evolution of True Citrus Species and the Hybrid Sweet Orange
Bibliographic record
Abstract
Pummelo (Citrus maxima) is considered as one of the true citrus species. Together with mandarin (C. reticulata), it gave rise to the hybrid sweet orange (C. sinensis) and other important citrus crops. Although these species have 2n = 18, each has a unique heterochromatin distribution. The aims of this study were to identify chromosome homoeologies between pummelo and other true citrus species, to investigate the karyotypic changes involved in the chromosomal evolution between true citrus and to shed light into the origin of sweet orange hybrid karyotype. Mitotic metaphase chromosomes of pummelo and sweet orange were double stained with the fluorochromes CMA/DAPI (Chromomycin A3/4’-6-diamidino-2-phenylindole), and identified by FISH (Fluorescence in Situ Hybridization) with chromosome-specific BAC (Bacterial Artificial Chromosome) markers. The results were compared to previously established cytogenetic maps of mandarin, C. medica and Poncirus trifoliata. Only chromosomes 1, 4 and 8 were maintained unaltered among species, with chromosomes 2 and 3 being among the least conserved in heterochromatin distribution. BACs were conserved in position among homoeologs and the markers mapped to chromosomes 2 and 3 indicated that sweet orange karyotype largely conserved one chromosome from pummelo and one from mandarin. Despite conserved synteny, expansion and contraction of heterochromatic blocks accounted for the differences between karyotypes, even between the hybrid sweet orange and pummelo.
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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 | 0.000 |
| 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) | 0.001 | 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".