Herbicide drift exposure leads to reduced herbicide sensitivity in Amaranthus spp.

Abstract

While the introduction of herbicide tolerant crops provided growers new options to manage weeds, the widespread adoption of these herbicides increased the risk for herbicide spray drift to surrounding vegetation. the impact of herbicide drift in sensitive crops is extensively investigated, whereas scarce information is available on the consequences of herbicide drift in non-target plants. Weeds are often abundant in field margins and ditches surrounding agricultural landscapes. Repeated herbicide drift exposure to weeds could be detrimental to long-term management as numerous weeds evolved herbicide resistance following recurrent-selection with low herbicide rates. the objective of this study was to evaluate if glyphosate, 2,4-D, and dicamba spray drift could select Amaranthus spp. biotypes with reduced herbicide sensitivity. palmer amaranth and waterhemp populations were recurrently exposed to herbicide drift in a wind tunnel study over two generations. Seeds from survival plants were used for the subsequent rounds of herbicide drift exposure. progenies were subjected to herbicide doseresponse studies following drift selection. Herbicide drift exposure rapidly selected for Amaranthus spp. biotypes with reduced herbicide sensitivity over two generations. Weed management programs should consider strategies to mitigate near-field spray drift and suppress the establishment of resistance-prone weeds on field borders and ditches in agricultural landscapes.Some researchers also suggest that low rates of herbicides could induce new stress-related mutations and epigenetic alterations on weeds, ultimately leading to reduced herbicide sensitivity [33][34][35] .Recombination and accumulation of minor resistance alleles can occur at a faster rate in cross-pollinated species, such as Palmer amaranth and waterhemp, during recurrent selection with low rates of herbicides 21,22,36 . These C4 summer annual Amaranthus spp. are among the most troublesome weed species in the US row crop production systems 37 . Both are obligate outcrossing dioecious weed species with a fast growth habitat, extended emergence window, and prolific seed production with high genetic plasticity which pose a challenge to their management 37-44 . Numerous Palmer amaranth and waterhemp populations have evolved resistance to herbicides that target 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), 4-hydroxyphenylpyruvate dioxygenase (HPPD), photosystem II, protoporphyrinogen oxidase (PPO), auxin receptors, microtubule assembly, and acetolacte synthase (ALS) in the US 15,17,[45][46][47][48][49][50][51][52][53][54] . Moreover, pollen mediated gene flow has been reported as a major contributor to herbicide resistance dissemination in Palmer amaranth and waterhemp in the US Midwest 55,56 .Although controlling weed populations on field margins and ditches is considered a best management practice to delay herbicide resistance evolution, these weed populations are often neglected in agricultural landscapes [15][16][17]29 . The hypothesis of this study is that rep...

Mechanisms of evolved herbicide resistance

“…Empirical support for creeping resistance is provided by low-dose selection of experimental populations. Such studies, conducted with different species and different herbicides, have consistently demonstrated the ability of plants to evolve increased herbicide resistance (in some cases by many fold) after only two or three generations (176)(177)(178). That such a shift in herbicide response was due to the accumulation of multiple alleles was supported by a follow-up study on one of the selected populations that indicated at least three loci were involved.…”

Dicamba drift alters plant-herbivore interactions at the agro-ecological interface

“…Dicamba use is on an upwards trajectory in agriculture due to the adoption of dicamba-tolerant crops (USDA- ERA, 2018). However, this herbicide can drift to non-target areas, causing significant damage to unprotected crops and natural plant populations (Egan et al 2014, Bohnenblust et al 2016, Jones et al 2018, Vieira et al 2020). Currently, we understand little about how the widespread use of dicamba may impact non-target organisms and even less about whether dicamba drift may impact plant-insect interactions.…”

“…A broad expectation is that exposure to a synthetic auxin, such as dicamba, could alter plant allocation towards growth and defence, and potentially lead to increased vulnerability to herbivores, in line with growth-defense tradeoff framework (Coley, Bryant, Chapin 1985). Recent work has shown that exposure to drift rates of herbicides like dicamba can lead to the evolution of reduced herbicide sensitivity (Vieria et al 2020) and recurrent selection of low dose herbicides can lead to nontarget site resistance (Busi et al 2013), however there is little understanding of how this process may influence selection for allocation herbivory defense.…”

Survey of ground and aerial herbicide application practices in Arkansas agronomic crops

“…Herbicide drift to roadsides and field borders caused by application miscues has led to the evolution of herbicide resistance within two generations of Amaranthus spp. (Vieira et al 2020). As a result, focus should be placed on using precise application procedures to maximize efficacy of herbicide applications while maintaining environmental safety (Matthews et al 2014).…”