Resistance Mechanisms to 2,4-D in Six Different Dicotyledonous Weeds Around the World

Abstract

2,4-D resistance is increasing around the world due to both transgenic crops and resistance to other herbicides. The objective of the this study was to characterize the currently unknown mechanisms of 2,4-D resistance in five weed species from around the globe: Amaranthus hybridus (Argentina), Conyza canadensis (Hungary), Conyza sumatrensis (France), Hirschfeldia incana (Argentina) and Parthenium hysterophorus (Dominican Republic), using Papaver rhoeas (Spain) as a standard resistant (R) species. Dose-response trials using malathion and absorption, translocation and metabolism experiments were performed to unravel the resistance mechanisms. R plants produced at least 3-folds less ethylene than susceptible plants, confirming the resistance to 2,4-D, together with resistance factors >4. A. hybridus, P. hysterophorus and P. rhoeas showed both reduced translocation and enhanced metabolism. In the two Conyza sps., the only resistance mechanism found was enhanced metabolism. Malathion synergized with 2,4-D in all these species, indicating the role of cytochrome P450 in the herbicide degradation. In H. incana, reduced translocation was the only contributing mechanism to resistance. Among the six dicotyledonous weed species investigated, there was a differential contribution to 2,4-D resistance of enhanced metabolism and reduced translocation. Thus, extrapolating 2,4-D resistance mechanisms from one weed species to another is very risky, if even related.

Multiple Resistance to Glyphosate and 2,4-D in Carduus acanthoides L. from Argentina and Alternative Control Solutions

“…The differences in the accumulation of ethylene by the susceptible population fluctuated exponentially with respect to the increase in the rate, while resistant population accumulation was constant. These results could indicate the existence of non-target site resistance mechanisms (NTSR), such as reduced translocation and recently shown 2,4-D metabolism, in different dicotyledonous species [11,44,45].…”

Cytochrome P450 metabolism-based herbicide resistance to imazamox and 2,4-D in Papaver rhoeas

“…ha − 1 of amitrole dissolved in water. Rates were based on previous studies (Oliveira et al, 2018;Palma-Bautista et al, 2020;Torra et al, 2017). After approximately 120 min, either 2,4-D or imazamox were applied at 600 g a.i.…”

“…In the case of synthetic auxin herbicides (SAHs), NTSR by means of enzymes that metabolize them is more rare (Busi et al, 2018). Few cases have reported the potential role of P450s in the degradation of SAH in HR broadleaf weeds (Torra et al, 2017;Figueiredo et al, 2018;Shergill et al, 2018;Gaines et al, 2020;Palma--Bautista et al, 2020;Todd et al, 2020).…”

Herbicide Resistance and Management Options of Papaver rhoeas L. and Centaurea cyanus L. in Europe: A Review

“…Recently, cell death has also been discovered as an NTSR mechanism [100]. Weed species can show one or more mechanisms within NTSR to synthetic auxins and, as Palma-Bautista et al [101] demonstrate in their study of six different dicotyledonous weeds resistant to 2,4-D, extrapolating the mechanism from one weed species to another is very risky. The molecular mechanisms of NTSR in weeds remain to be elucidated.…”

“…The relationship between impaired translocation and enhanced metabolism remains unclear and requires investigation [83]. One of the hypotheses proposed is that reduced translocation might be a secondary effect of enhanced metabolism [101]. Based on qPCR, within five hours of herbicide application, Scarabel et al [103] detected an increase in GH3 (indole-3-acetic acid amido synthetase) and GST3 (glutathione S-transferase)-two genes upregulated following 2,4-D treatment-confirming their involvement in plant response to 2,4-D.…”