Tribenuron-methyl metabolism and the rare Pro197Phe double mutation together with 2,4-D metabolism and reduced absorption can evolve in Papaver rhoeas with multiple and cross herbicide resistance to ALS inhibitors and auxin mimics

Prevalence, spatial structure and evolution of resistance to acetolactate‐synthase (ALS) inhibitors and 2,4‐D in the major weed Papaver rhoeas (L.) assessed using a massive, country‐wide sampling

“…The doublemutant Phe197 allele had recently been identified in poppy and predicted to confer resistance using ALS modelling. 25 However, its role in resistance, as well as that of the other novel alleles identified in our work, remains to be formally demonstrated.…”

“…Thus, detection of mutations at all ALS codons involved in herbicide resistance in weeds could have been expected in poppy, which is far from being the case: our work firmly established that the vast majority of resistance-endowing ALS alleles having evolved in poppy carry an amino-acid substitution at codon 197, as also observed in previous works. 15,18,19,[23][24][25][26] This strongly suggests that ALS alleles carrying mutations at other codons critical for herbicide sensitivity may impair enzyme activity, incurring a fitness cost that prevents them from increasing in frequency and spreading. Indeed, non-codon-197 mutant alleles were only observed in very low frequencies in one or few populations (Table 1), except allele Leu574.…”

“…In contrast, resistance to ALS inhibitors in poppy is chiefly due to mutant ALS alleles. 15,18,19,[23][24][25][26] Non-ALS-based resistance also exists in this species, 19,24,25,27,28 but is most often associated to mutant ALS alleles. 24,25,29 This makes poppy an excellent candidate for herbicide resistance diagnosis based on massive parallel ALS sequencing, all the more so as a number of studies in the domains of weed science, enzymology or crystallography have pinpointed at least 42 ALS codons with a proven or a possible role in sensitivity to ALS inhibitors.…”

“…15,18,19,[23][24][25][26] Non-ALS-based resistance also exists in this species, 19,24,25,27,28 but is most often associated to mutant ALS alleles. 24,25,29 This makes poppy an excellent candidate for herbicide resistance diagnosis based on massive parallel ALS sequencing, all the more so as a number of studies in the domains of weed science, enzymology or crystallography have pinpointed at least 42 ALS codons with a proven or a possible role in sensitivity to ALS inhibitors. [30][31][32][33][34] Of those, nine proven determinants of resistance have been observed in weeds from the field (codons 122, 197, 205, 206, 376, 377, 574, 653 and 654; codon numeration is standardised to the Arabidopsis sequence as recommended), 35,36 12 have been reported in laboratory mutants (121, 124, 196, 199, 203, 256, 351, 352, 375, 570, 571 and 578), and the rest have been identified on the basis of molecular docking or crystallography data (119,120,123,194,195,198,200,201,202,207,208,378,568,569, 575 and 655 to 660).…”

An Asp376Glu substitution in ALS gene and enhanced metabolism confers high tribenuron-methyl resistance in Sinapis alba

“…However, metabolism studies showed that TM is metabolized faster to non-toxic compounds (OH-MM and MM-conjugate) in resistant populations. OH-MM is formed thanks to the activity of P450 while MM-conjugate thanks to GS, in a wellknown degradation route for TM in broadleaf weeds (Cruz-Hipoĺito et al, 2013;Palma-Bautista et al, 2022). It has been shown in recent years that cases of resistance due to metabolism are increasing mainly in grass weeds, as specified in the introduction section.…”