Characterization of mutations in the membrane‐anchored subunits AaSDHC and AaSDHD of succinate dehydrogenase from <i>Alternaria alternata</i> isolates conferring field resistance to the fungicide boscalid
Bibliographic record
Abstract
The molecular basis of resistance to the fungicide boscalid in 25 Alternaria alternata field mutants exhibiting resistance to boscalid and previously tested negative for AaSDHB mutations conferring boscalid resistance was investigated by cloning and sequencing the A. alternata SDHC ( AaSDHC ) and SDHD ( AaSDHD ) genes from a boscalid‐sensitive isolate. The SDHB and SDHC/SDHD genes encode the iron sulphur and two membrane‐anchored subunits of succinate:ubiquinone oxidoreductase (SQR) that constitute the boscalid fungicide molecular targets. The deduced amino acid sequences exhibited low similarities with SDHC and SDHD peptides from other organisms, but residues essential to form the ubiquinone binding site or important in SQR assembly were particularly conserved. Sequence comparisons of the AaSDHC and AaSDHD genes between resistant mutants and wild‐type isolates revealed that two highly conserved histidine residues implicated in the heme b ligation and located at codon 134 in AaSDHC (22 mutants) and codon 133 in AaSDHD (two mutants) were replaced by arginine residues (H134R and H133R). In another mutant, a substitution of an aspartate by a glutamic acid occurred at amino acid position 123 (D123E) in AaSDHD. Additional tests revealed that mycelial growth of boscalid‐resistant isolates was reduced when isolates were subjected to oxidative stress. The identified mutations were confirmed using PCR‐RFLP assays. This is apparently the first report of mutations located in the heme b ligands of the cytochrome II gene associated with carboxamide resistance.
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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 | 0.000 | 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 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".