Investigations of 2,4-D and Multiple Herbicide Resistance in a Missouri Waterhemp (Amaranthus tuberculatus) Population

Abstract

Research was conducted from 2015 to 2017 to investigate the potential for 2,4-D and multiple herbicide resistance in a waterhemp [Amaranthus tuberculatus(Moq.) J. D. Sauer] population from Missouri (designated MO-Ren). In the field, visual control of the MO-Ren population with 0.56 to 4.48 kg 2,4-D ha−1ranged from 26% to 77% in 2015 and from 15% to 55% in 2016. The MO-Ren population was highly resistant to chlorimuron, with visual control never exceeding 7% either year. Estimates of the 2,4-D dose required to provide 50% visual control (I50) of the MO-Ren population were 1.44 kg ha−1compared with only 0.47 kg 2,4-D ha−1for the susceptible population. Based on comparisons to a susceptible population in dose–response experiments, the MO-Ren population was approximately 3-fold resistant to 2,4-D, and 7-, 7-, 22-, and 14-fold resistant to atrazine, fomesafen, glyphosate, and mesotrione, respectively. Dicamba and glufosinate were the only two herbicides that provided effective control of the MO-Ren population in these experiments. Examinations of multiple herbicide resistance at the individual plant level revealed that 16% of the plants of the MO-Ren population contained genes stacked for six-way herbicide resistance, and only 1% of plants were classified as resistant to a single herbicide (glyphosate). Results from these experiments confirm that the MO-RenA. tuberculatuspopulation is resistant to 2,4-D, atrazine, chlorimuron, fomesafen, glyphosate, and mesotrione, making this population the third 2,4-D–resistantA. tuberculatuspopulation identified in the United States, and the first population resistant to six different herbicidal modes of action.

Molecular and physiological characterization of six‐way resistance in an Amaranthus tuberculatus var. rudis biotype from Missouri

“…The multiple‐resistant A. tuberculatus biotype (MO‐Ren) investigated in this study was collected from a field in Randolph County, Missouri (39.32°N, −92.39°W) that had been in a continuous soybean production and had a history of repeated glyphosate, fomesafen, and 2,4‐ D use as a pre‐plant burndown. Subsequent field and glasshouse dose‐response experiments confirmed six‐way resistance to 2,4‐ D , glyphosate, fomesafen, chlorimuron, atrazine, and mesotrione . After herbicide resistance confirmation, fresh leaf tissue samples were collected from surviving plants in the last run of the dose‐response experiment(s) to examine the herbicide resistance mechanisms.…”

“…Two additional A. tuberculatus populations with multiple resistance to 2,4‐ D ( 2,4 ‐ dichlorophenoxyacetic acid) and other herbicides have been found; the first case was in Nebraska in 2009, followed by Illinois in 2016 . We recently reported an A. tuberculatus biotype, MO‐Ren, from Missouri, USA, with resistance to six SOA groups that include synthetic auxins, EPSPS‐, ALS‐, PPO‐, PSII‐, and HPPD‐inhibitors …”

“…14 We recently reported an A. tuberculatus biotype, MO-Ren, from Missouri, USA, with resistance to six SOA groups that include synthetic auxins, EPSPS-, ALS-, PPO-, PSII-, and HPPD-inhibitors. 15 Studies have revealed different mechanisms contribute to herbicide resistance in A. tuberculatus. Target-site point mutations corresponding to amino acids Trp574 and Ser653 16 and metabolism-based non-target-site mechanism(s) 17 have been reported to confer resistance to ALS-inhibiting herbicides.…”

A family affair: resistance mechanism and alternative control of three Amaranthus species resistant to acetolactate synthase inhibitors in Italy

“…A. retroflexus evolved multiple resistance to two classes of PSII (HRAC group C1 and C2), to ALS and PSII inhibitors, whereas another biotype proved to be resistant to ALS and PPO inhibitors . Dioecious species evolved a number of complex two‐ and three‐way multiple resistance with A. tuberculatus that became multiple resistant to up to six SoA (ALS, PSII, EPSPS, PPO, HPPD inhibitors and synthetic auxins) . The ability of these latter species to rapidly evolve herbicide‐resistant biotypes could be related to their reproductive system.…”

“…12 Dioecious species evolved a number of complex two-and three-way multiple resistance 6 with A. tuberculatus that became multiple resistant to up to six SoA (ALS, PSII, EPSPS, PPO, HPPD inhibitors and synthetic auxins). 13 The ability of these latter species to rapidly evolve herbicide-resistant biotypes could be related to their reproductive system. Since they are obligate outcrossers, they have high genetic recombination rates leading to a higher genetic and phenotypic variability in comparison to monoecious (selfing) Amaranthus species.…”