Department of Plant Sciences, University of California, Davis, CA 95616, USA.
Department of Plant Sciences, University of California, Davis, CA 95616, USA.
Pestic Biochem Physiol. 2023 Jun;193:105444. doi: 10.1016/j.pestbp.2023.105444. Epub 2023 Apr 28.
Weed resistance to acetohydroxyacid synthase (AHAS) inhibiting herbicides has been a critical issue for rice growers worldwide since the early 1990's. In California, resistance to bensulfuron-methyl was first detected in Cyperus difformis in 1993. Since then, populations of most major weeds of rice in California have been reported to show resistance to at least one AHAS inhibitor. We sought to describe the magnitude and mechanisms of AHAS inhibitor cross-resistance in California populations of C. difformis. Sixty-two populations were collected and screened for cross-resistance to bensulfuron-methyl (BEN), halosulfuron-methyl (HAL), bispyribac‑sodium (BIS), and penoxsulam (PEN), revealing six major patterns of cross-resistance. Representative C. difformis populations from each cross-resistance pattern were then subjected to dose-response, cytochrome P450 inhibition, AHAS gene sequencing, and metabolic studies with the same herbicides as in the screening. Dose-response confirmed the detected resistances in the representative populations, and suggested that the majority of observed resistance was dose-dependent. Cytochrome P450 inhibition via malathion revealed evidence of increased metabolic activity in resistant populations to BEN, BIS, and PEN. AHAS gene sequencing revealed amino acid substitutions in five of six populations: R3 (Pro197-Ser), R4 (Pro97-His), R10 (Asp376), R41 (Ala122-Asn), and R18 (Trp574-Leu). Metabolic studies confirmed evidence of increased activity of cytochrome P450s in all populations. Metabolic BEN and HAL analysis did not yield similar results to malathion inhibition, suggesting different P450's or other pathways. Taken together, the results of the studies confirm the complexity of AHAS inhibitor cross-resistance in C. difformis, and the presence of both target-site and metabolic resistance in most of the representative populations underscores the importance of proper herbicide selection, rotation, and scouting in fields.
自 20 世纪 90 年代初以来，杂草对乙酰羟酸合酶（AHAS）抑制剂类除草剂的抗性一直是全球稻农面临的一个关键问题。在加利福尼亚州，1993 年首次在异型莎草中检测到对苯磺隆-甲基的抗性。此后，加利福尼亚州水稻的大多数主要杂草种群都被报道至少对一种 AHAS 抑制剂具有抗性。我们试图描述加利福尼亚州异型莎草种群中 AHAS 抑制剂的交叉抗性的程度和机制。收集了 62 个种群进行苯磺隆-甲基（BEN）、甲磺隆-甲基（HAL）、双吡氟-钠（BIS）和吡嘧磺隆（PEN）的交叉抗性筛选，揭示了六种主要的交叉抗性模式。然后，对每种交叉抗性模式的代表性异型莎草种群进行剂量反应、细胞色素 P450 抑制、AHAS 基因测序以及与筛选中相同除草剂的代谢研究。剂量反应证实了代表性种群中检测到的抗性，并且表明大多数观察到的抗性是剂量依赖性的。通过马拉硫磷进行的细胞色素 P450 抑制显示出在抗性种群中 BEN、BIS 和 PEN 的代谢活性增加的证据。AHAS 基因测序揭示了六个种群中的五个种群的氨基酸取代：R3（Pro197-Ser）、R4（Pro97-His）、R10（Asp376）、R41（Ala122-Asn）和 R18（Trp574-Leu）。代谢研究证实了所有种群中细胞色素 P450 活性增加的证据。代谢苯磺隆和甲磺隆分析与马拉硫磷抑制没有产生类似的结果，这表明存在不同的 P450 或其他途径。综上所述，研究结果证实了异型莎草中 AHAS 抑制剂交叉抗性的复杂性，并且大多数代表性种群中存在靶标和代谢抗性，这强调了正确选择、轮换和田间侦察除草剂的重要性。
