Palmer amaranth (Amaranthus palmeri S. Watson) populations resistant to acetolactate synthase (ALS)-inhibiting herbicides and glyphosate are fairly common throughout the state of North Carolina (NC). This has led farm managers to rely more heavily on herbicides with other sites of action (SOA) for A. palmeri control, especially protoporphyrinogen oxidase and glutamine synthetase inhibitors. In the fall of 2016, seeds from A. palmeri populations were collected from the NC Coastal Plain, the state’s most prominent agricultural region. In separate experiments, plants with 2 to 4 leaves from the 110 populations were treated with field use rates of glyphosate, glufosinate-ammonium, fomesafen, mesotrione, or thifensulfuron-methyl. Percent visible control and survival were evaluated 3 wk after treatment. Survival frequencies were highest following glyphosate (99%) or thifensulfuron-methyl (96%) treatment. Known mutations conferring resistance to ALS inhibitors were found in populations surviving thifensulfuron-methyl application (Ala-122-Ser, Pro-197-Ser, Trp-574-Leu, and/or Ser-653-Asn), in addition to a new mutation (Ala-282-Asp) that requires further investigation. Forty-two populations had survivors after mesotrione application, with one population having 17% survival. Four populations survived fomesafen treatment, while none survived glufosinate. Dose–response studies showed an increase in fomesafen needed to kill 50% of two populations (LD50); however, these rates were far below the field use rate (less than 5 g ha−1). In two populations following mesotrione dose–response studies, a 2.4- to 3.3-fold increase was noted, with LD90 values approaching the field use rate (72.8 and 89.8 g ha−1). Screening of the progeny of individuals surviving mesotrione confirmed the presence of resistance alleles, as there were a higher number of survivors at the 1X rate compared with the parent population, confirming resistance to mesotrione. These data suggest A. palmeri resistant to chemistries other than glyphosate and thifensulfuron-methyl are present in NC, which highlights the need for weed management approaches to mitigate the evolution and spread of herbicide-resistant populations.

中文翻译：

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从北卡罗来纳州沿海平原采集的种质中，棕榈苋（Amaranthus palmeri）对除草剂的敏感性

帕尔默苋菜（苋菜S. Watson）对乙酰乳酸合酶（ALS）抑制性除草剂和草甘膦具有抗性的种群在整个北卡罗来纳州（NC）相当普遍。这导致农场管理者更加依赖具有其他作用点 (SOA) 的除草剂A. 帕尔梅里控制，尤其是原卟啉原氧化酶和谷氨酰胺合成酶抑制剂。2016 年秋季，种子来自A. 帕尔梅里人口来自北卡罗来纳州沿海平原，该州最突出的农业区。在单独的实验中，来自 110 个种群的具有 2 到 4 片叶子的植物用草甘膦、草铵膦、氟磺胺草醚、甲基磺草酮或噻吩磺隆的田间使用率进行处理。治疗后 3 周评估可见控制百分比和存活率。草甘膦 (99%) 或噻吩磺隆 (96%) 处理后的存活率最高。在噻吩磺隆应用（Ala-122-Ser、Pro-197-Ser、Trp-574-Leu 和/或 Ser-653-Asn）幸存的人群中发现了赋予 ALS 抑制剂抗性的已知突变，此外还有一种新的需要进一步研究的突变（Ala-282-Asp）。甲基磺草酮应用后有 42 个人群存活，其中 1 个人群存活率为 17%。四个人群在氟虫胺治疗中幸存下来，而没有一个人在草铵膦治疗中幸存下来。剂量反应研究表明杀死 50% 的两个人群（LD50); 然而，这些比率远低于田间使用率（少于 5 g ha-1）。在甲基磺草酮剂量反应研究后的两个人群中，注意到 2.4 到 3.3 倍的增加，LD90值接近田间使用率（72.8 和 89.8 g ha-1）。对甲基磺草酮存活个体后代的筛选证实了抗性等位基因的存在，因为与亲代种群相比，1X 比率的幸存者数量更多，从而证实了甲基磺草酮的抗性。这些数据表明A. 帕尔梅里NC 中存在对除草甘膦和噻吩磺隆以外的化学物质的抗性，这突出表明需要采取杂草管理方法来减轻抗除草剂种群的演变和传播。