Department of Crop Sciences, University of Illinois, Urbana, IL, USA.
Pest Manag Sci. 2020 Sep;76(9):3139-3148. doi: 10.1002/ps.5868. Epub 2020 May 19.
Two waterhemp (Amaranthus tuberculatus) populations from Illinois demonstrating multiple-resistance to acetolactate synthase (ALS)-, 4-hydroxyphenylpyruvate dioxygenase, and photosystem II (PSII)-inhibiting herbicides (designated CHR and SIR) also displayed reduced sensitivity to very-long-chain fatty acid-inhibiting herbicides, including S-metolachlor. We hypothesized that a physiological mechanism, such as enhanced metabolism, could be responsible for the reduced efficacy of S-metolachlor.
Metabolism experiments indicated that resistant populations degraded S-metolachlor more rapidly than sensitive populations and equally as rapidly as corn 2-24 h after treatment (HAT). Resistant waterhemp and corn metabolized 90% (DT ) of absorbed S-metolachlor in less than 3.2 h whereas DT values for sensitive waterhemp exceeded 6 h. The glutathione S-transferase inhibitor 4-chloro-7-nitrobenzofurazon and cytochrome P450-inhibitor malathion decreased the amount of S-metolachlor metabolized in resistant waterhemp at 4 HAT but not in sensitive waterhemp or corn, and altered the abundance of certain metabolites in resistant waterhemp.
Results from this research demonstrate that resistance to S-metolachlor in these waterhemp populations is due to enhanced herbicide metabolism relative to sensitive populations. In addition, our results indicate that resistant waterhemp might utilize metabolic pathway(s) more intricate than either sensitive waterhemp or corn based on their metabolite profiles. © 2020 Society of Chemical Industry.
来自伊利诺伊州的两种豚草（Amaranthus tuberculatus）种群对乙酰乳酸合酶（ALS）、4-羟基苯丙酮酸双加氧酶和光系统 II（PSII）抑制剂除草剂（分别命名为 CHR 和 SIR）具有多重抗性，同时对非常长链脂肪酸抑制剂除草剂，包括 S-甲草氯，表现出敏感性降低。我们假设一种生理机制，如增强代谢，可能是导致 S-甲草氯效果降低的原因。
代谢实验表明，抗性种群比敏感种群更快地降解 S-甲草氯，并且与玉米在处理后 2-24 小时（HAT）同样快地降解。抗性豚草和玉米在不到 3.2 小时内代谢了 90%（DT）的吸收 S-甲草氯，而敏感豚草的 DT 值超过 6 小时。谷胱甘肽 S-转移酶抑制剂 4-氯-7-硝基苯并呋咱和细胞色素 P450 抑制剂马拉硫磷在 4 HAT 时降低了抗性豚草中 S-甲草氯的代谢量，但在敏感豚草或玉米中则没有，并且改变了抗性豚草中某些代谢物的丰度。
这项研究的结果表明，这些豚草种群对 S-甲草氯的抗性是由于与敏感种群相比，除草剂代谢增强所致。此外，我们的结果表明，基于代谢物谱，抗性豚草可能利用比敏感豚草或玉米更复杂的代谢途径。 © 2020 化学工业协会。
