Abstract：
BACKGROUND: Japanese brome (Bromus japonicus Thumb.) is one of the problematic annual weeds in winter wheat (Triticum aestivum L.) and is generally controlled by acetolactate synthase (ALS) inhibitors. Repeated use of the ALS inhibitor propoxycarbazone-Na resulted in the evolution of resistance to this herbicide in three B. japonicus populations, i.e., R1, R2, and R3 in Kansas (KS). However, the level of resistance and mechanism conferring resistance in these populations is unknown. The objectives of this research were to (i) evaluate the level of resistance to propoxycarbazone-Na in R1, R2, and R3 in comparison with a known susceptible population (S1), (ii) investigate the mechanism of resistance involved in conferring ALS-inhibitor resistance, and (iii) investigate the cross-resistance to other ALS inhibitors.
RESULTS: Dose-response (0 to 16x; x = 44 g ai ha-1 of propoxycarbazone-Na) assay indicated 167, 125, and 667-fold resistance in R1, R2 and R3 populations, respectively, compared to S1 population. ALS gene sequencing confirmed the mutations resulting in amino acid substitutions, i.e., Pro-197-Thr (R3, R1)/Ser (R2, R1) bestowing resistance to these ALS inhibitors. Such amino acid substitutions also showed differential cross-resistance to sulfosulfuron, mesosulfuron-methyl, pyroxsulam, and imazamox among resistant populations. Pretreatment with malathion (a cytochrome P450 enzyme-inhibitor) followed by imazamox treatment suggested cross-resistance to this herbicide possibly via metabolism only in R3 population.
CONCLUSIONS: Overall, these results confirm the first case of target-site based resistance to ALS inhibitors in B. japonicus in the US, highlighting the need for exploring herbicides with alternative modes of action to enhance weed control in winter wheat. © 2024 Society of Chemical Industry.
RESULTS: Dose-response (0 to 16x; x = 44 g ai ha-1 of propoxycarbazone-Na) assay indicated 167, 125, and 667-fold resistance in R1, R2 and R3 populations, respectively, compared to S1 population. ALS gene sequencing confirmed the mutations resulting in amino acid substitutions, i.e., Pro-197-Thr (R3, R1)/Ser (R2, R1) bestowing resistance to these ALS inhibitors. Such amino acid substitutions also showed differential cross-resistance to sulfosulfuron, mesosulfuron-methyl, pyroxsulam, and imazamox among resistant populations. Pretreatment with malathion (a cytochrome P450 enzyme-inhibitor) followed by imazamox treatment suggested cross-resistance to this herbicide possibly via metabolism only in R3 population.
CONCLUSIONS: Overall, these results confirm the first case of target-site based resistance to ALS inhibitors in B. japonicus in the US, highlighting the need for exploring herbicides with alternative modes of action to enhance weed control in winter wheat. © 2024 Society of Chemical Industry.
摘要：
背景：日本Brome（BromusjaponicusThumb。）是冬小麦（TriticumaestivumL.）中存在问题的一年生杂草之一，通常由乙酰乳酸合酶（ALS）抑制剂控制。重复使用ALS抑制剂丙氧卡巴酮-Na导致三个日本芽孢杆菌种群对这种除草剂的抗性演变，即，堪萨斯州(KS)的R1、R2和R3。然而,这些人群中的抗性水平和赋予抗性的机制尚不清楚。这项研究的目的是（i）与已知的易感人群（S1）相比，评估R1，R2和R3中对丙氧卡巴酮-Na的抗性水平，（ii）研究与赋予ALS抑制剂抗性有关的抗性机制，和(iii)研究与其他ALS抑制剂的交叉抗性。
结果：剂量反应（0至16x；x=44gaiha-1的丙氧基卡巴酮-Na）测定表明R1，R2和R3群体的抗性为167、125和667倍，分别,与S1人口相比。ALS基因测序证实了导致氨基酸取代的突变，即，Pro-197-Thr(R3,R1)/Ser(R2,R1)赋予这些ALS抑制剂抗性。此类氨基酸取代还显示出对磺基磺隆的不同交叉抗性，甲基甲磺隆，pyroxsulam,抗性种群中的imazamox。用马拉硫磷（一种细胞色素P450酶抑制剂）进行预处理，然后进行imazamox处理，表明对这种除草剂的交叉抗性可能仅在R3人群中通过代谢进行。
结论：总体而言，这些结果证实了美国日本芽孢杆菌对ALS抑制剂的第一例基于靶位点的耐药性，强调需要探索具有替代作用方式的除草剂，以增强冬小麦的杂草控制。©2024化学工业学会。
结果：剂量反应（0至16x；x=44gaiha-1的丙氧基卡巴酮-Na）测定表明R1，R2和R3群体的抗性为167、125和667倍，分别,与S1人口相比。ALS基因测序证实了导致氨基酸取代的突变，即，Pro-197-Thr(R3,R1)/Ser(R2,R1)赋予这些ALS抑制剂抗性。此类氨基酸取代还显示出对磺基磺隆的不同交叉抗性，甲基甲磺隆，pyroxsulam,抗性种群中的imazamox。用马拉硫磷（一种细胞色素P450酶抑制剂）进行预处理，然后进行imazamox处理，表明对这种除草剂的交叉抗性可能仅在R3人群中通过代谢进行。
结论：总体而言，这些结果证实了美国日本芽孢杆菌对ALS抑制剂的第一例基于靶位点的耐药性，强调需要探索具有替代作用方式的除草剂，以增强冬小麦的杂草控制。©2024化学工业学会。
