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BACKGROUND: The early detection of herbicide resistance in weeds is a key factor to avoid herbicide waste and improve agriculture sustainability. The present study aimed to develop and validate an allele‐specific loop‐mediated isothermal amplification (AS‐LAMP) assay for the quick on‐site detection of the resistance‐endowing point mutation Trp‐574‐Leu in the acetolactate synthase (ALS) gene in three widely diffused Amaranthus weed species: Amaranthus retroflexus, Amaranthus hybridus and Amaranthus tuberculatus. RESULTS: The AS‐LAMP protocol was developed on wild‐type and ALS‐mutant plants of the three species and revealed that the amplification approach with only the primer set specific for the mutant allele (574‐Leu) was the most promising. The validation and estimation of the AS‐LAMP performance evaluated by comparing the results with those of the molecular marker (cleaved amplified polymorphic sequences) indicated that, although the sensitivity and specificity were relatively high in all species (overall 100 and > 65%, respectively), precision was high for A. hybridus L. and A. retroflexus L. (75 and 79%, respectively), but quite low for A. tuberculatus (Moq.) J. D. Sauer (59%). The LAMP assay was also effective on crude genomic DNA extraction, allowing the quick detection of mutant plants in field situation (on site resistance detection). CONCLUSION: The proposed AS‐LAMP method has proven to be a promising technique for rapid detection of resistance as a result of Trp‐574‐Leu on the two monoecious weedy Amaranthus species but resulted less effective in the genetically variable dioecious species A. tuberculatus. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

BACKGROUND: Several soybean fields in Italy were found to be infested by multiple species of Amaranthus spp. not adequately controlled by acetolactate (ALS) inhibitor herbicides. The objectives of this research were (i) to create a simplified botanical key to identify weedy amaranths; (ii) to determine the number and type of sites of action the accession are resistant to, i.e. resistance pattern; and (iii) to determine the main resistance mechanisms involved d) to evaluate the efficacy of herbicides with different site of action. RESULTS: An easy‐to‐use botanical key was devised and successfully used in the infested sites and results were confirmed through a species‐specific molecular marker. Amaranthus retroflexus L. (redrood pigweed) was found in three sites; plants with Asp376Glu substitution at the ALS gene were resistant to thifensulfuron‐methyl. Amaranthus tuberculatus (Moq.) J.D.Sauer (waterhemp) and Amaranthus hybridus L. (smooth pigweed) accessions were cross‐resistant to thifensulfuron‐methyl and imazamox; most ALS‐resistant plants had a point mutation at position 574. One A. hybridus accession had the substitution Trp574Met, new for Amaranthus genus. All ALS‐resistant accessions were controlled by glyphosate and metribuzin. A. retroflexus accessions were controlled by bentazon, instead an A. hybridus and some A. tuberculatus accession were not. CONCLUSIONS: The simplified botanical key proposed herein could be a useful tool for farmers and weed scientists to reliably identify Amaranthus species in the field. The main resistance mechanism in the three Amaranthus species is target‐site mediated. This is the first evidence of ALS‐resistant A. tuberculatus outside its native North American range. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The article presents a study which aims to characterise the genetic and molecular level of two field-resistant of Schoenoplectus mucronatus' populations. Through the Southern blot analyses, multiple of acetolactate synthase (ALS) gene were identified and were characterised by cytosine methylation. It concludes that mutated genes give resistance to ALS. It cites that the resistance pattern differs on the frequency of resistant genotypes, which affect the effectivity of ALS-inhibiting herbicides.

Lolium spp. are troublesome weeds mainly found in winter cereal crops worldwide, including Europe. In recent years resistant mechanisms have been evolved to several important herbicides. In this study we investigated the mechanisms responsible for conferring glyphosate resistance in some Lolium spp. populations. A holistic approach was used, based on dose-response experiments, determination of shikimic acid concentration in plant leaf tissue, as well as molecular analyses. More specifically, in three Lolium spp. populations the existence of a mutation in the Pro-106 codon of the 5-enolpyruvylshikimate-3 phosphate synthase (EPSPS) gene was investigated as well as the relative transcript levels of four ABC-transporter genes were monitored at three time points after glyphosate application. The results demonstrated that glyphosate resistance is a multifactor phenomenon. Relative transcript levels of the ABC-transporter genes were abundant at very early time points after glyphosate treatments. Dose-response experiments and shikimate analyses were in accordance with the findings of the quantitative PCR (qPCR) analyses. We suggest that relative expression ratio of ABC-transporter genes can be a useful tool to rapidly identify Lolium spp. populations resistant to glyphosate. [ABSTRACT FROM AUTHOR]

Herbicides have facilitated weed management but their incorrect use can lead to environmental contamination. Reducing herbicide use by limiting their application to a band along the crop row can decrease their environmental impact. Three field experiments were conducted in North-eastern Italy to evaluate herbicide band application systems integrated with inter-row hoeing for silage maize. Post-emergence herbicide band application (sprayed area 50% of total field; herbicide dose 50% of that recommended, application with an inter-row cultivator prototype) was compared with pre-emergence band application (sprayed area 33% of total field; herbicide dose 33% of that recommended, application with a seeder) and pre-emergence broadcast application (sprayed area 100% of total field; full recommended herbicide dose, application with a boom sprayer) that is standard management for maize. Weed density and composition were evaluated before and after post-emergence herbicide application and at crop harvest. Crop yield was also recorded. Weed density in untreated areas ranged between 5 and 15 plants m−2 in the different experiments. Optimal weed control and good yields were achieved without significant differences between all treatments. Herbicide band application can provide optimal weed control in silage maize, at the same time allowing a relevant reduction of herbicide input. [ABSTRACT FROM AUTHOR]