Table 2. List of herbicide treatments, herbicide resistance mechanism(s), and genotypes of Palmer amaranth (Amaranthus palmeri S. Watson) treated to chlorimuron-ethyl, fomesafen, and glyphosate separately and in all possible combinations in the greenhousea.
| Herbicide treatment | Rate | Resistance mechanism(s) testedb | Total possible genotypes | Genotypes identified in surviving herbicide treated plantsc |
|---|---|---|---|---|
| g ai or ae ha-1 | ────────── # ────────── | |||
| Chlorimuron-ethyl | 39 | Trp574Leu | 3 | 3 |
| Fomesafen | 1,026 | ΔG210 | 3 | 2 |
| Glyphosate | 2,500 | Amplified EPSPS | 2 | 1 |
| Chlorimuron-ethyl plus fomesafen | 39 plus 1,026 | Trp574Leu and ΔG210 | 9 | 2 |
| Chlorimuron-ethyl plus glyphosate | 39 plus 2,500 | Trp574Leu and Amplified EPSPS | 6 | 3 |
| Fomesafen plus glyphosate | 1,026 plus 2,500 | ΔG210 and amplified EPSPS | 6 | 3 |
| Chlorimuron-ethyl plus fomesafen plus glyphosate | 39 plus 1,026 plus 2,500 | Trp574Leu, ΔG210, and amplified EPSPS | 18 | 7 |
a Abbreviations: EPSPS, 5-enolpyruvylshikimate-3-phosphase synthase;
b Alleles for Trp574Leu and ΔG210 resistance mechanisms were heterozygous, homozygous-resistant, or wild type for a total of three possible genotypes. Two genotypes were possible for EPSPS copy number. Plants with ten or more EPSPS copies possessed the EPSPS amplified genotype and plants with EPSPS copy number from 1 to 9 were denoted as the wild type.
c Confirmed herbicide-resistant genotypes using molecular screening assays.