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In both 2,4-D and glyphosate cases, a potential reduced herbicide translocation resistance mechanism could be related to ABC transporters (Pan et al., [42]), however, alterations in translocation and cell exclusion resulting in 2,4-D and glyphosate resistance were not identified with the RN phenotype. Although reduced glyphosate translocation was described as a resistance mechanism long ago, only recently the first glyphosate cell membrane carrier has been identified (ABCC-type transporter) conferring glyphosate resistance in I E. colona i (Pan et al., [42]). Resistance to ALS, ACCase, and EPSPS inhibiting herbicides are the most reported cases in this Research Topic, with 8, 7, and 5 contributions, respectively, which agrees with the SoA herbicides most related to herbicide resistance worldwide (Heap, [31]). Keywords: cross-resistance; cytochrome P450 monooxygenase (CYP450); enhanced herbicide metabolism; glutathione-S-transferase (GST); glyphosate; rapid necrosis EN cross-resistance cytochrome P450 monooxygenase (CYP450) enhanced herbicide metabolism glutathione-S-transferase (GST) glyphosate rapid necrosis 1 5 5 11/01/21 20211028 NES 211028 Evolution of Multiple Survival Mechanisms The acquired inheritable trait of plants to survive and reproduce under herbicide exposure is defined as resistance. [Extracted from the article]

Echinochloa spp. is one of the most invasive weeds in rice fields worldwide. Acetolactate synthase (ALS) and acetyl-CoA carboxylase (ACCase) inhibiting herbicides are two of the most widely used rice herbicides. However, overuse has led to the resistance evolution of Echinochloa spp. to penoxsulam (ALS-inhibitor) and cyhalofop-methyl (ACCase-inhibitor). In this work, 137 different Echinochloa spp. populations were collected in different rice fields in Extremadura (western Spain) where lack of control was detected. Target-site based resistance (by sequencing ALS and ACCase gene) and characterization of Echinochloa species at the molecular level (based on PCR-RFLP analyses) were carried out in those populations. Most of the populations studied (111 of 137) belong to the E. oryzicola/E. oryzoides group. Three-point mutations were identified in ALS genes: Pro197Ser, Pro197Thr, and Ser653Asn, the first being the most frequent substitution in resistant plants. In the ACCase gene, the Ile1781Leu substitution was found. In both ALS and ACCase sequencing, evidence of heterozygosity was also observed. To assess whether cross-resistance patterns differed between mutations, two populations belonging to the E. oryzicola/E. oryzoides group had its most frequent mutations (Pro197Ser, population ech3-14 and Ile1781Leu, population ech114-10) chosen to be carried out in a dose-response assay. It was confirmed that Pro197Ser conferred resistance to triazolopyrimidine, imidazolinone, sulfonylurea, and pyrimidinyl benzoate families. On the other hand, the Ile1781Leu change gave resistance to aryloxyphenoxypropionate and cyclohexanedione families. Of the authorized herbicides in rice in Spain, more that 80% belong to these families. It is therefore important that farmers carry out an integrated control system that combines both chemical and non-chemical tools. [ABSTRACT FROM AUTHOR]

Amaranthus palmeri is the most prominent invasive weed in agricultural land from North America, partly due to its propensity to evolve resistance to multiple herbicide sites of action. In the last two decades, reports of this species have increased throughout the American continent and occasionally in other continents. In 2007, A. palmeri populations were found in three localities in northeastern Spain, and they are still present today. To determine whether these three populations resulted from a common or independent introduction events—and when and from where they could have occurred—research was carried out aiming to characterize the resistance profile and mechanisms to 5-enolpyruvylshikimate-3-phosphate synthase-and acetolactate synthase (ALS)-inhibiting herbicides and to analyze the relationship between these three populations using inter simple sequence repeat DNA fingerprinting. Dose–response trials confirmed that the three populations were susceptible to glyphosate but resistant to nicosulfuron-methyl. Resistance to ALS inhibitors was due to several amino acid substitutions in positions Pro197, Trp574 and Ser653. Moreover, the substitutions Ser653Ile and Pro197Thr are described for the first time in this species. At field-labeled rates, all populations were fully controlled with alternative herbicides with other sites of action. Amaranthus palmeri individuals were clustered in three groups based on unweighted pair group method with arithmetic mean analysis, which corresponded to the three sampled populations, with a 67% of genetic relationship among them. Considering this high genetic variability and the different positions and amino acid substations found between populations, it was hypothesized that different colonization events occurred from the American continent probably prior to the introduction of glyphosate resistant crops. Prevention from new introductions is warranted because new herbicide resistance traits could arrive, complicating the management of this invasive weed species, while managing or eradicating the already established populations. [ABSTRACT FROM AUTHOR]