Resistance to acetohydroxyacid synthase-inhibiting herbicides in populations of eastern black nightshade (Solanum Ptycanthum Dun.) from Ontario
Bibliographic record
Abstract
Resistance to acetohydroxyacid synthase (AHAS) inhibitors in populations of eastern black nightshade has been rising rapidly in Ontario. The objectives of this study were to (i) identify the spectrums of resistance to different AHAS inhibiting herbicides, (ii) identify effective alternative mode-of-action herbicides, (iii) examine how the resistant (R) AHAS behaves in response to different herbicide and end-product concentrations, (iv) determine the molecular basis of resistance, (v) determine the inheritance of resistance and the genetic variability among geographically distinct populations, and (vi) ascertain whether the resistant populations suffered from a fitness penalty under various light, watering, temperature, and intraspecific competition conditions. Compared to a susceptible (S) population one of the R populations had 726-, 31-, 6-, and 4-fold resistance to imazethapyr, imazamox, primisulfuron, and flumetsulam, respectively. There was no cross resistance in those populations to chloroacetamide herbicides. These results were confirmed with in vitro enzyme assays. Moreover, the resistant enzyme had lower activity and was less sensitive to feedback inhibition from branched-chain amino acids compared to the susceptible enzyme. The results of 'AHAS' sequencing revealed that resistance in twelve populations was due to an Ala205Val substitution, while in one population it was due to Ala122Thr substitution. A single nuclear gene, with incomplete dominance, controlled resistance to AHAS-inhibiting herbicides in R populations of eastern black nightshade. Random Amplified Polymorphic DNA (RAPD) analysis identified four distinct groups of populations, suggesting that resistance could have occurred as a result of both local selection pressure and gene flow. Fitness experiments under various light, watering, and temperature regimes, as well as competition studies indicated that under optimal reproductive conditions, Ala205Val is associated with a fitness cost in plants. There was no impact on above ground biomass production but there was a reduction in berry production and a delay in the maturation of berries. The higher concentration of branched-chain amino acids could be the reason for the lower fitness of the R populations, by diverting the resources away from the reproductive function of the mutant plants. However, the Ala205Val substitution could have modified the wild type phenotypes to adapt to stressful environments.
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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 | 0.001 | 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) | 0.001 | 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".