Coexistence of target-site and non-target-site mechanisms of glyphosate resistance in Amaranthus palmeri populations from Argentina

ABSTRACT. Amaranthus palmeri S. Waston is currently one of the most problematic weeds worldwide. Biotypes with resistance to herbicides such as glyphosate and ALS inhibitors are now present in almost all Argentinian cultivable areas. In this work, we studied glyphosate resistance in three different populations, some of them previously characterized as resistant to ALS inhibitors. Dose-response curves were conducted in order to assess the effect of glyphosate on the survival and dry biomass of the populations. Subsequently, the presence of target-site resistance (TSR) was studied. Results confirmed the glyphosate resistance in the three populations, showing different levels of resistance, being R2 and R3 significantly more resistant than r1 population. A high prevalence of the P106S substitution was detected in the three resistant populations, while none increase in the relative EPSPS copy number was noticed. Some surviving plants without any of the TSR mechanisms for glyphosate were detected in R3 population, suggesting the presence of non-target-site resistance (NTSR).

摘要 帕尔默苋（Amaranthus palmeri S. Waston）是当前全球范围内危害最为严重的恶性杂草之一。对草甘膦（glyphosate）及乙酰乳酸合酶（acetolactate synthase，ALS）抑制剂类除草剂产生抗性的生物型，现已遍及阿根廷几乎所有可耕地。本研究针对三个不同种群开展草甘膦抗性相关研究，其中部分种群此前已被鉴定为对ALS抑制剂类除草剂具有抗性。为评估草甘膦对各供试种群存活率及干生物量的影响，我们开展了剂量-反应曲线试验。随后，我们对靶标位点抗性（target-site resistance，TSR）的存在情况进行了检测。研究结果证实三个供试种群均对草甘膦具有抗性，且抗性水平存在差异：R2与R3种群的抗性显著高于r1种群。在三个抗性种群中均检测到高比例的P106S氨基酸替换，而未观察到5-烯醇丙酮酰莽草酸-3-磷酸合酶（5-enolpyruvylshikimate-3-phosphate synthase，EPSPS）基因拷贝数的相对增加。在R3种群中，我们发现了部分未携带任何已知草甘膦靶标位点抗性机制的存活植株，这提示该种群可能存在非靶标位点抗性（non-target-site resistance，NTSR）机制。