Target-site and non-target-site resistance mechanisms to ALS inhibiting herbicides in Papaver rhoeas

Abstract

Target-site and non-target-site resistance mechanisms to ALS inhibitors were investigated in multiple resistant (tribenuron-methyl and 2,4-D) and only 2,4-D resistant, Spanish corn poppy populations. Six amino-acid replacements at the Pro197 position (Ala197, Arg197, His197, Leu197, Thr197 and Ser197) were found in three multiple resistant populations. These replacements were responsible for the high tribenuron-methyl resistance response, and some of them, especially Thr197 and Ser197, elucidated the cross-resistant pattern for imazamox and florasulam, respectively. Mutations outside of the conserved regions of the ALS gene (Gly427 and Leu648) were identified, but not related to resistance response. Higher mobility of labeled tribenuron-methyl in plants with multiple resistance was, however, similar to plants with only 2,4-D resistance, indicating the presence of non-target-site resistance mechanisms (NTSR). Metabolism studies confirmed the presence of a hydroxy imazamox metabolite in one of the populations. Lack of correlation between phenotype and genotype in plants treated with florasulam or imazamox, non-mutated plants surviving imazamox, tribenuron-methyl translocation patterns and the presence of enhanced metabolism revealed signs of the presence of NTSR mechanisms to ALS inhibitors in this species. On this basis, selection pressure with ALS non-SU inhibitors bears the risk of promoting the evolution of NTSR mechanisms in corn poppy.

Weed resistance to synthetic auxin herbicides

“…There are biotypes of corn poppy resistant to ALS‐inhibiting and phenoxy‐carboxylate herbicides that can degrade imazamox . It is unknown whether the same cytochrome P450 degrades herbicides with these modes of action or if other enzymes could be involved.…”

“…There are biotypes of corn poppy resistant to ALS-inhibiting and phenoxy-carboxylate herbicides that can degrade imazamox. 20 It is unknown whether the same cytochrome P450 degrades herbicides with these modes of action or if other enzymes could wileyonlinelibrary.com/journal/ps be involved. The herbicide, 2,4-D, was found to induce glycoside hydrolase (GH3) and glutathione S-transferase (GST3) expression in susceptible and resistant P. rhoeas plants, thus increased expression of these enzymes did not appear to be involved in resistance to 2,4-D. 21 There is a need to identify the genes and to more fully understand the mechanisms involved in corn poppy herbicide resistance.…”

Enzymatic activity and chlorophyll fluorescence imaging of maize seedlings (Zea mays L.) after exposure to low doses of chlorsulfuron and cadmium

“…Chlorsulfuron inhibit acetolactate synthase (ALS) which is a important enzyme in the biosynthesis of valine, leucine and isoleucine. A previous study reported that a high level of resistance in plants is due to substitutions at Pro197 to sulfonylurea herbicides (Rey-Caballero et al 2017).…”

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

“…These populations displayed a survival of >90% at the recommended field dose (480 g ai ha −1 ) for Amaranthus hybridus, Hirschfeldia incana and Parthenium hysterophorus, or at 600 g ai ha −1 for Conyza canadensis and Papaver rhoeas, while it was~25% for Conyza sumatrensis (data not shown). 2,4-D S populations belonging to these species were originally harvested from areas close to the fields evolving resistance to this herbicide, except for P. rhoeas in which a known S standard was used [13,27]. Seeds were maintained at 4 • C in a cold chamber and they had more than an 80% germination rate during this study.…”

“…The plants were harvested at 96 HAT. Previous experiments with different dicotyledonous weeds, such as P. rhoeas, established this time point to be the most suitable for finding maximum differences between S and R populations to SAH [13,27,30,31]. The unabsorbed 14 C-herbicide was removed from the treated leaf with a water-acetone solution (1:1 v/v) by washing the plants three times separately with 1 mL of that solution.…”