Chemical control has become less effective for the invasive weed species horseweed (Conyza canadensis) found in tangerine (Citrus reticulate) orchards of Korea. The dose–response assays of the biotypes of C. canadensis collected in 2017 from the Jeju province of Korea demonstrated that the amount of glyphosate needed for 50% growth reduction (GR₅₀) in the glyphosate-resistant (GR) biotype was up to 100 times greater than that in the glyphosate-susceptible (GS) biotype (0.328 kg a.e. ha⁻¹). However, the mechanism of resistance in the GR populations of C. canadensis in Korea is unknown. Therefore, this study aimed to determine the mechanism of resistance to glyphosate in the Korean C. canadensis populations. Shikimic acid accumulation and 5-enolpyruvyl shikimate-3-phosphate synthase (EPSPS) gene expression were analyzed in a GR and a GS biotype of C. canadensis. The GR biotype showed less shikimic acid accumulation than the GS biotype. A target point mutation in the sequence encoding the Pro 106 of EPSPS1 was not found after sequencing the GR biotype. Moreover, the expression level of EPSPS1 was not altered significantly following application of glyphosate to the GS and GR biotypes, whereas the levels of M10 and M11 ABC transporter genes which play an important role in plant growth and nutrition, and the interaction of the plant with its environment were found to be slightly higher in the glyphosate-treated GS and GR biotypes than the untreated control plants. Our results show that M10 and M11 are likely to be involved in the glyphosate resistance mechanism in C. canadensis. Consequently, non-chemical control methods should be implemented to manage or slow the spread of glyphosate resistance in C. canadensis.

对于韩国柑橘（柑橘）果园中发现的入侵杂草马草（Conyza canadensis），化学防治已变得不太有效。2017 年从韩国济州省收集的加拿大 C. canadensis生物型的剂量反应分析表明，草甘膦抗性 (GR) 生物型生长减少 50% (GR ₅₀ ) 所需的草甘膦量高达 100比草甘膦敏感 (GS) 生物型 (0.328 kg ae ha ^-1 )多倍。然而，韩国C. canadensis GR 种群的抗性机制尚不清楚。因此，本研究旨在确定韩国人对草甘膦抗性的机制。C. canadensis种群。在加拿大 C. canadensis的 GR 和 GS 生物型中分析莽草酸积累和 5-烯醇丙酮酸莽草酸-3-磷酸合酶( EPSPS ) 基因表达。GR 生物型显示出比 GS 生物型更少的莽草酸积累。在对 GR 生物型进行测序后，未发现编码EPSPS1 Pro 106 的序列中的靶点突变。此外，EPSPS1的表达水平将草甘膦应用于 GS 和 GR 生物型后没有显着改变，而在植物生长和营养中起重要作用的 M10 和 M11 ABC 转运蛋白基因的水平以及植物与其环境的相互作用被发现略有变化草甘膦处理的 GS 和 GR 生物型高于未处理的对照植物。我们的研究结果表明，M10 和 M11 可能参与C. canadensis的草甘膦抗性机制。因此，应实施非化学控制方法来管理或减缓加拿大 C.草甘膦抗性的传播。