Multiple resistance to glyphosate and imazethapyr in Bidens subalternans

ABSTRACT Glyphosate has been widely used to control greater beggarticks populations that are resistant to acetolactate synthase (ALS) inhibitors in South America. However, herbicide control failures has been observed over the last three growing seasons in grain production areas of Paraguay. In this research, we report the first case of multiple resistance to glyphosate (EPSPs) and imazethapyr (ALS) in greater beggarticks (Bidens subalternans) population from Paraguay. This conclusion was supported by dose-response experiments conducted in two consecutive years (2018 and 2019) with a putative resistant (R) and a susceptible (S) population. Alternative herbicides were also tested for post-emergence control of R population. For glyphosate, the resistant factor (RF) values were 8.8- (2018) and 15.7-fold (2019). For imazethapyr, the RF values were 59- and 58-fold, in 2018 and 2019, respectively. Treatments with 2,4-D, dicamba, 2,4-D + glyphosate, dicamba + glyphosate, lactofen, fomesafen, ammonium-glufosinate, atrazine, and bentazon provided more than 80% control of the R population. This is the first case of multiple resistance to glyphosate and imazethapyr in greater beggarticks (Bidens subalternans) in the world. The mechanisms underlying resistance in this biotype should be evaluated in future research.摘要 草甘膦（glyphosate）在南美洲被广泛用于防控对乙酰乳酸合成酶（ALS）抑制剂产生抗药性的大狼把草（Bidens subalternans）种群。然而，过去三个生长季中，巴拉圭粮食产区均出现了除草剂防控失效的情况。本研究首次报道了巴拉圭境内该种群对草甘膦（EPSPS）与咪唑乙烟酸（imazethapyr）产生多重抗药性的案例。该结论通过2018至2019连续两年的剂量反应实验得以验证，实验所用材料为疑似抗药性（R）与敏感型（S）种群。本研究同时测试了多款可用于该抗药性种群芽后防控的替代除草剂。针对草甘膦，抗药性因子（RF）在2018年为8.8倍，2019年达15.7倍；针对咪唑乙烟酸，2018年与2019年的抗药性因子分别为59倍与58倍。采用2,4-滴、麦草畏、2,4-滴+草甘膦、麦草畏+草甘膦、乳氟禾草灵、氟磺胺草醚、草铵膦铵盐、莠去津以及苯达松进行处理，可对该抗药性种群实现80%以上的防控效果。本研究为全球范围内首次报道大狼把草（Bidens subalternans）对草甘膦与咪唑乙烟酸产生多重抗药性的案例，该生物型的抗药性机制有待后续研究阐明。