Table 1. Location of Indiana fields where Palmer amaranth (Amaranthus palmeri S. Watson) seeds were collected in 2013 and the herbicide resistance profile assigned for each county based on A. palmeri injury (0–100%) to chlorimuron-ethyl (39 g ai ha-1), fomesafen (1,026 g ai ha-1), and glyphosate (2,500 g ae ha-1) in the initial screen for herbicide resistance experiment.
| Countya | Coordinates | Herbicide resistance profileb | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Chlorimuron-ethyl | Fomesafen | Glyphosate | |||||||||
| Latitude | Longitude | R | MR | S | R | MR | S | R | MR | S | |
| Washington | 38.75°N | 86.06°W | X | X | X | ||||||
| Daviess | 38.85°N | 87.08°W | X | X | X | ||||||
| Cass | 40.86°N | 86.20°W | X | X | X | ||||||
| Unknowncd | NA | NA | ── | ── | ── | ── | ── | ── | ── | ── | ── |
a A. palmeri seeds from suspected herbicide-resistant plants were collected from agricultural production fields infested with A. palmeri. A. palmeri seeds from the unknown county were purchased from Azlin Seed Service, Leland, MS. The site location of the unknown population was not available.
b A herbicide resistance profile was assigned to counties based on visible injury of surviving A. palmeri in the initial screen for herbicide resistance experiment: R, resistant (0–40% injury); MR, moderately resistant (41–80% injury); and S, susceptible (81–100% injury).
c A. palmeri from the unknown county was not evaluated in the initial screen for herbicide resistance experiment, but was included as a glyphosate-sensitive check.
d A total of twenty plants from the unknown county were tested for amplified 5-enolpyruvylshikimate-3-phosphase synthase and ΔG210 mutations that confer resistance to glyphosate and fomesafen, respectively, and no plants possessed either herbicide resistant trait. The Trp574Leu amino acid substitution mutation that confers resistance to acetolactase synthase inhibiting herbicides was identified in A. palmeri from the unknown location.