Department of Genetics and Biochemistry, Clemson University, Clemson, SC, USA.
Department of Soil and Crop Sciences, Texas A&M University, College Station, TX, USA.
Pest Manag Sci. 2019 Apr;75(4):1131-1139. doi: 10.1002/ps.5232. Epub 2018 Dec 10.
Palmer amaranth (Amaranthus palmeri S. Wats) is one of the most common and troublesome weeds in the USA. Palmer amaranth resistance to acetolactate synthase (ALS) inhibitors is widespread in the USA, as in Arkansas. The cross-resistance patterns and mechanism of resistance are not known. Experiments were conducted to determine cross-resistance to ALS inhibitors and identify target-site mutations in 20 Palmer amaranth localities from 13 counties in Arkansas.
All Palmer amaranth localities tested had plants cross-resistant to imazethapyr, flumetsulam, primisulfuron, pyrithiobac and trifloxysulfuron. The dose of trifloxysulfuron that caused 50% control was 21-56-fold greater for resistant accessions than for susceptible ones. All but three resistant plants analyzed had one or two relative copies of ALS; one plant had seven relative copies. All resistant plants tested (18 localities) carried the Trp574Leu mutation, which is known to confer broad resistance to ALS inhibitors, supporting the cross-resistance pattern observed. Besides the Trp574Leu mutation, 30% of localities had individuals with one additional resistance-conferring mutation including Ala122Thr, Pro197Ala or Ser653Asn.
The Trp574Leu mutation in ALS is the primary mechanism of resistance to ALS inhibitors in Palmer amaranth from Arkansas, USA. In some localities, multiple mutations have accumulated in one plant. All localities tested contained plants with resistance to five families of ALS inhibitors. Localities with extremely high resistance to ALS inhibitors, and those outside the subset we studied, may harbor non-target site resistance mechanisms. ALS inhibitors are generally no longer effective on Palmer amaranth in these localities from the US mid-south. © 2018 Society of Chemical Industry.
马齿苋（Amaranthus palmeri S. Wats）是美国最常见和最麻烦的杂草之一。在美国，包括阿肯色州在内，马齿苋对乙酰乳酸合成酶（ALS）抑制剂的抗性很普遍。交叉抗性模式和抗性机制尚不清楚。本研究旨在确定 20 个来自阿肯色州 13 个县的马齿苋种群对 ALS 抑制剂的交叉抗性，并鉴定靶标位点突变。
所有测试的马齿苋种群对咪草烟、氟噻草胺、砜嘧磺隆、吡嘧磺隆和三氟啶磺隆均具有交叉抗性。抗性品系对三氟啶磺隆的剂量比敏感品系高出 21-56 倍。分析的除三株外的所有抗性植株均具有一个或两个相对拷贝的 ALS；一株植物有七个相对拷贝。所有测试的抗性植株（18 个种群）均携带 Trp574Leu 突变，该突变已知能赋予 ALS 抑制剂的广泛抗性，支持观察到的交叉抗性模式。除了 Trp574Leu 突变外，30%的种群个体还具有一个额外的抗性赋予突变，包括 Ala122Thr、Pro197Ala 或 Ser653Asn。
阿肯色州美国马齿苋中 ALS 对 ALS 抑制剂的主要抗性机制是 ALS 中的 Trp574Leu 突变。在一些种群中，一个植物中积累了多个突变。所有测试的种群都含有对 5 种 ALS 抑制剂家族具有抗性的植株。对 ALS 抑制剂具有极高抗性的种群，以及不在我们研究范围内的种群，可能具有非靶标抗性机制。在这些来自美国中南部的种群中，ALS 抑制剂通常对马齿苋不再有效。 © 2018 英国化学学会。
