Association between metabolic resistances to atrazine and mesotrione in a multiple-resistant waterhemp (Amaranthus tuberculatus) population

Abstract

Metabolic resistances to atrazine (atz-R) and mesotrione (meso-R) occur in several waterhemp [Amaranthus tuberculatus (Moq.) Sauer] populations in the United States. Interestingly, although metabolic atz-R but mesotrione-sensitive A. tuberculatus populations have been reported, an Amaranthus population has not been confirmed as meso-R but atrazine-sensitive, implying an association between these traits. Experiments were designed to investigate whether the single gene conferring metabolic atz-R plays a role in meso-R. An F2 population was generated from a multiple herbicide–resistant A. tuberculatus population from McLean County, IL (MCR). A cross was made between a known meso-R male clone (MCR-6) and a herbicide-sensitive female clone from Wayne County, IL (WCS-2) to develop an F1 population. Survival of MCR-6 plants following atrazine POST treatment (14.4 kg ha−1) indicated the male parent was homozygous atz-R. F1 plants were intermated to obtain a segregating pseudo-F2 population. Dose–response and metabolic studies conducted with mesotrione using F1 plants indicated intermediate biomass reductions and metabolic rates compared with MCR-6 and WCS. F2 plants were initially treated with either mesotrione (260 g ha−1) or atrazine (2 kg ha−1) POST, and after 21 d of recovery, vegetative clones from surviving resistant plants were subsequently treated with the other herbicide. When mesotrione was applied first, the meso-R frequency was 8.2%, and when atrazine was applied first, the atz-R frequency was 75%. However, the meso-R frequency increased to 16.5% following preselection for atz-R, and 100% of surviving meso-R plants were atz-R. Our findings indicate that the gene conferring metabolic atz-R is also involved with the meso-R trait within the population tested.

Herbicide resistance in Amaranthus tuberculatus†

“…For this reason, and because of already widespread atrazine resistance, it was not particularly surprising that HPPD‐inhibitor‐resistant A. tuberculatus populations routinely were reported to also be resistant to atrazine 28 . A very recent report, however, indicates there may be a physiological basis for this association 75 . Specifically, in a segregating F 2 population, plants that were atrazine resistant were more likely to be resistant to mesotrione, and all plants resistant to mesotrione were atrazine resistant.…”

“…28 A very recent report, however, indicates there may be a physiological basis for this association. 75 Specifically, in a segregating F 2 population, plants that were atrazine resistant were more likely to be resistant to mesotrione, and all plants resistant to mesotrione were atrazine resistant. The investigators proposed that the gene (likely AtuGSTF2) conferring atrazine resistance contributed to mesotrione resistance.…”

“…The investigators proposed that the gene (likely AtuGSTF2 ) conferring atrazine resistance contributed to mesotrione resistance. Because no glutathione–mesotrione conjugates were identified, the GST conferring atrazine resistance was hypothesized to contribute to HPPD‐inhibitor resistance by detoxifying lipid peroxides and reactive oxygen species 75 . Regardless of how AtuGSTF2 contributes to resistance to HPPD inhibitors, evidence that it does is a promising step forward in understanding the multigenic nature of resistance to HPPD inhibitors.…”

Is There a Benefit of Adding Atrazine to HPPD-Inhibiting Herbicides for Control of Multiple-Herbicide-Resistant, Including Group 5-Resistant, Waterhemp in Corn?

“…Moreover, the combination of HPPD-inhibitors with other MOA increases the spectrum of weed control and delays the evolution of herbicide resistance, which will allow future use of currently effective MOA. The occurrence of MHR waterhemp resistant to both HPPD-inhibitors and atrazine (Jacobs et al, 2020;McMullan & Green, 2011) as well as Palmer amaranth Jhala et al (2014) suggests these herbicides should be used strategically, and growers should strive for 100% control. The ability of MHR waterhemp to escape herbicide applications, germinate late in the growing season, produce a plethora of viable offspring and evolve resistance to multiple herbicide MOA necessitates full-season control programs.…”

Genetic architecture underlying HPPD-inhibitor resistance in a Nebraska Amaranthus tuberculatus population

“…Indeed, numerous studies have pointed towards cytochrome P450s as being pivotal for resistance to the herbicide group 8–15 . Recently, Jacobs et al reported a tight association between resistance to atrazine and a component of a complex HPPD-inhibitor resistance phenotype in A. tuberculatus 44 . While atrazine resistance in the tested population is mediated by a glutathione S -transferase (Ma et al 2013), the mechanism of resistance to HPPD-inhibitors is unknown.…”