Abstract Background Gomphrena perennis (Gpe) and G. pulchella (Gpu) are perennial glyphosate-tolerant amaranthaceous weeds of central and northern Argentina where glyphosate-resistant soybeans are grown with no-till. The study of weeds leaves morphoanatomy is important to understand environmental adaptation and could be used to explain herbicide absorption. Leaf surfaces of Gomphrena species were previously described for phylogenetic studies, and morphoanatomy of two Gomphrena perennis populations was characterized for glyphosate tolerance. There are no reports on comparative studies of Gpe and Gpu. We hypothesize that these two species differ in their morpho anatomical characteristics. Objective The aim of this research was to characterize and compare their leaf morphoanatomy throughout their life cycle. Methods Fully developed leaves of the upper middle third were extracted from plants grown in pots in a greenhouse at three phenological stages: eight true leaves (S1), beginning of branching (S2), and full flowering (S3). In both leaf sides, densities of epidermal cells, stomata and trichomes, and ostiole lengths were quantified. In main and secondary bundle anatomic parameters were measured: thickness of total blade, upper and lower epidermis, and mesophyll, and sheath length. Results Both species are amphiestomatic. Gpu had higher stomata densities in lower epidermis than Gpe at S1. Gpu had higher trichome densities than Gpe, whereas the latter presented higher values in anatomic variables mainly in secondary bundle (total blade and total mesophyll) at all stages. Conclusions There were no marked differences in the morphoanatomy between the two species throughout their life cycle.

Abstract Background Phytoremediation is a technique used in soils contaminated with residual herbicides, such as tebuthiuron. However, the herbicide presence in the soil and plant matrices are not generally quantified. Objective This study aimed to select plant species to evaluate the phytoremediation of 14C-tebuthiuron by showy rattlepod (Crotalaria spectabilis), sorghum (Sorghum bicolor), radish (Raphanus sativus), peanut (Arachis hypogaea), and alfalfa (Medicago sativa) in herbicide-contaminated soil. Methods The selection of the five herbicide phytoremediation plants was with the application of five rates of tebuthiuron (300, 600, 1,200, 2,400, and 4,800 g a.i. ha-1) and compared to a control. Peanuts and sorghum (herbicide-tolerant plants) were sown in soil contaminated with tebuthiuron (600 g a.i. ha-1) applied through a working solution containing 17.47 kBq of 14C-tebuthiuron. The total of herbicide was analyzed in the soil and plant at three phenological stages. Results Showy rattlepod, radish, and alfalfa were sensitive to the herbicide even at the lowest application rate. Sorghum was tolerant to the herbicide up to 600 g ha-1 with the application of 1,200 g ha-1, there was 80% injury; peanut was tolerant even at the highest rate (4,800 g ha-1) with only 40% injury. Peanut and sorghum were able to phytoremediate the soil, although, peanut was more efficient in decreasing tebuthiuron contamination by 76%, while sorghum reduced at by 45% at 3rd phenological stage. Conclusions Thus, both plants can be recommended in succession/rotation with crops that had tebuthiuron applied from pre-emergence weed control.

Abstract Background Diversified crop systems provide several advantages for crop production and the agricultural ecosystem. In contrast, growing the same crop for consecutive years increases weeds, insects, and diseases issues, adding further cost to crop production owing to their management. Objective The objective was to evaluate the effects of six different winter cover crops and compare the impacts of a diversified rotation system in contrast to the succession system, combined with three different post-emergence herbicide management looking up to soybean yield, aboveground mass production, and weed density impact. Methods The experiment was performed over 2014 to 2018, using a randomized block design with four replications. Cover crop treatments were 1) fallow 2) wheat 3) rye 4) rye + turnip 5) rye + vetch 6) black oats. At the time of cover crop termination, weed density was counted and aboveground mass was measured. The crop rotation system was an alternated soybean and corn using three different post-emergence herbicide treatments, and the succession system was soybean each year. When a significant effect was observed after test F, the Tukey test (p ≤ 0.05) was applied to compare treatment effects. Results Rye + vetch as a cover crop, rotation system, and herbicide usage showed a higher impact on weed density. Rye + turnip has produced more aboveground biomass. Soybean yield was higher after wheat. Conclusions Cover crops implementation, crop rotation system, and herbicide usage have increased biomass production and crop yield, and reduced weed density showing integrated weed management as a key strategy for production systems.

Abstract Background There is little information on how different soil cover systems influence the residual effect of pre-emergent herbicides used in soybean cultivation in Brazil. Objective The objective was to compare the persistence of different pre-emergent herbicides in a Latosolic Dystrophic Red Nitosol soil in the presence or absence of black oat straw on the soil surface. Methods The herbicides used were chlorimuron-ethyl (40.0 g ai ha-1), diclosulam (70.1 g ai ha-1), flumioxazin (100.0 ai g ha-1) and saflufenacil (70.0 g ai ha-1). Soil samples were collected at 0, 5, 10, 15, 20, 32, 46 and 60 days after herbicide application. The bioavailability of the herbicides was evaluated in a greenhouse using cucumber plants as bioindicators. Results Rainfall was necessary for the herbicides to go through the straw layer and reach the soil. Using straw, the half-life times for chlorimuron, diclosulam, flumioxazin and saflufenacil were 42, 61, 49 and 26 days, while without straw, they were 23, 45, 8 and 10 days, respectively. Conclusion The presence of straw on the soil surface increased the persistence of herbicides in the soil.

Abstract Background Diagnostic bioassays are used to screen the suspected R population. They are conducted at a single herbicide dose and evaluated at a specific time after treatment that can differentiate resistant from susceptible population. Objective Three different bioassays were evaluated to assess the detection of acetyl CoA carboxylase-inhibiting herbicides resistance in D. ciliaris. Method Increasing herbicide rates were used to evaluate the three bioassays for differentiating R from S populations. Results R1 and R2 differed from S in all employed bioassays. In the Agar-based gel box box assay, the S biotype had greater plant damage at the lower herbicide concentration relative to the R biotypes 3 DAT but differences between R and S decreased over time. In the leaf flotation assay, R biotypes floated at the lower concentration on the surface, whereas the leaves of S biotypes failed to float. For the electrical conductivity assay, the S biotype contained high electrical conductivity due to the high leaching of electrolyte into the water across all four herbicides tested than the R biotypes. Conclusion While these assays were able to separate R and S biotypes, the level of resistance difference for any assay was no greater than 40% depending on rating data and exposure dose. While a statistical separation could be achieved using a rate response regression analysis for these bioassays, our data highlights the challenges associated whether these methods could provide an obvious difference at any single rate or rating data to be used as a consistent, effective first-phase resistance screen.

Abstract Background Cutleaf geranium ( Geranium dissectum L) is a weed found in cereals and grasslands. Knowledge about the germination response of weeds under various environmental conditions is critical for their effective management, whereas such study has not been carried out thoroughly on this species. Objective This study was carried out to investigate the effect of some environmental factors on seed germination and emergence of cutleaf geranium. Methods The seeds were subjected to various environmental factors including water potentials, salinity, pH, high temperatures, burial depth and flooding at the temperature resulting in the highest germination (10 °C). All experiments were carried out twice, which were done consecutively. Results Germination percentage was halved at a water potential of -0.6 MPa, and no germination was observed at -2 MPa. Geranium dissectum seeds had negligible germination at 200 mM NaCl concentration. Seeds germinated over a pH range of 5-8, with the highest germination at pH between 6 and 7. Germination of this species reached from 85.0% after treatment at 80 °C but no seeds germinated after exposure to 120 °C. Maximum emergence was estimated 88.8%, which was halved at 2.2 cm depth. No emergence was observed at 4 cm or greater depths. Germination was 88.4% to 0% 15 days after flooding. Conclusions This species may not usually be found in areas with poor environmental conditions, and a semi-deep tillage or inclusion of rice in crop rotation may be used to control this weed.

Abstract Background Crop tolerance to herbicides and the effectiveness of weed control are key considerations of a chemical management program. Crop tolerance levels and the mechanism involved is of great importance in ensuring the safe use of an herbicide. Objective This study aims to evaluate the effect of mefenpyr-diethyl as a safener and metabolic inhibitor (organophosphorus insecticides) on the penoxsulam tolerance of white oat cultivars. Methods We determined the relative tolerance (%) of URS Guará and URS Guria white oat cultivars to different doses of penoxsulam with and without prior application of organophosphorus metabolic inhibitors (malathion + chlorpyrifos). We then determined the relative tolerance (%) of the white oat cultivar URS Guria with and without prior application of a protective metabolization stimulator (mefenpyr-diethyl). Results Increased penoxsulam doses resulted in lower relative tolerance of both cultivars. The application of organophosphorus insecticides reduced the penoxsulam tolerance of white oat cultivars, with a 14.4 and 4.8 fold reduction of C50 in the URS Guará and URS Guria cultivars, respectively. The use of mefenpyr-diethyl increased the penoxsulam tolerance of URS Guria by a factor of 2.62. Conclusions The penoxsulam tolerance of white oat cultivars was reduced by organophosphorus insecticides and increased by mefenpyr-diethyl. Metabolization is the likely mechanism of tolerance of white oats to this herbicide.

Abstract Background Among the weeds in Iran, resistant Lolium rigidum Gaud is considered a troublesome weed in winter cereals due to its tendency to evolve cross (CR) and multiple resistance (MR) to herbicides. Objective This research examined the patterns and mechanisms of L. rigidum resistance to clodinafop-propargyl (CP) and mesosulfuron methyl+iodosulfuron methyl (MI). Methods Experiments were conducted on four putative-resistant L. rigidum biotypes and one susceptible biotype. The dose-response assay was performed on the biotypes with CP and MI. CR and MR were investigated with haloxyfop-R-methyl (HRM), sethoxydim (SD), pinoxaden (PN). and isoproturon+ diflufenican (ID) herbicides. An indirect study of the metabolism of herbicides was carried out using the cytochrome P450 monooxygenase (CYP450) inhibitors 1-aminobenzotriazole (ABT), piperonyl butoxide (PBO) and malathion. Finally, sequencing of ALS and ACCase genes was performed to investigate target-site resistance. Results All putative-resistant L. rigidum biotypes were resistant to CP, MI, and HRM, but susceptible to SD, PN, and ID. The indirect study showed that the P450 enzyme had no role in the evolution of resistance in L. rigidum biotypes. Resistance in this species was due to Ile-1781-Leu and Pro-197-Ser substitutions on ACCase and ALS encoding genes led to resistance, respectively. Conclusions Resistance in the studied L. rigidum biotypes to ALS and ACCase inhibiting was due of target site resistance. If these resistant biotypes are not controlled, they will become a problem for farmers in the region.

Abstract Background Weed interference in the early stages of soybean development can compromise its yield. The use of herbicides with residual effects at the time of sowing is an alternative to reduce weed density and emergence time, consequently, the damage caused by their interference. Therefore, weed development can be reduced, which can result in easier post-emergence control. The combination of herbicide modes of action extends the spectrum of control and delays herbicide resistance evolution. Objective This work aimed to determine the onset of the critical period of weed control (CPWC) from the application of residual herbicides mixtures at soybean sowing. Methods Two experiments were carried out in 2021/2022, the first in a conventional tillage system with increasing periods of soybean/weeds coexistence (14, 28, 42, and 56 days after crop emergence). The second experiment consisted of a no-tillage system with soybean/weeds coexistence for 30, 45, 60, 75, and 90 days after crop emergence. On the day of soybean sowing, mixtures of the herbicides diclosulam + pyroxasulfone, flumioxazin + pyroxasulfone and diuron + sulfentrazone were applied, in addition to the untreated check. Soybean yield was evaluated evaluated upon harvest and data compared by non-linear regressions to CPWC determination. Results The application of residual herbicides can allowing reduces losses relative to the untreated control by up to 57%. CPWC beginning can be extended from eight to forty days, depending on mixes and acceptable losses. Conclusions The use of the mixture of residual herbicides are a good option for weed interference reduction for soybean crop.

Abstract Background Field bindweed (Convolvulus arvensis L.) is a hardy perennial weed currently threatening many agroecosystems and orchard ecosystems in China. It can be spread farther by seed with a long dormancy. Objective This study aimed to evaluate the seasonal changes in germinability, dormancy and viability of field bindweed seeds in the unique arid environment in northwest China. Methods Seeds were subject to burial at various depths in the field, outdoor and indoor storage, or dry- and wet-cold stratification (5 C) treatments for 12 months. Seed germinability was tested at monthly intervals. Results No seed at 0- or 1-cm burial depths germinated in situ. Seeds buried at 3-20 cm started to germinate after 4 months, with steady increase in germination in situ over the next 7-month burial period. Some ungerminated seeds under field conditions released dormancy and could germinate ex situ under optimal laboratory conditions. The rapid dormancy release occurred under outdoor storage conditions and 13%–30% seed germinated ex situ. However, seeds from the indoor storage maintained a high level of dormancy with germination less than 12%. The dry/cold stratification was more effective in breaking seed dormancy than the wet/cold treatment. Most of the seeds (> 87%) retained their viability during the 12-month period. Conclusions Low temperature could partially break seed dormancy of field bindweed. The optimal emergence depth was 3–5 cm and the best time to control this weed species was from April to October. In view of the high seed viability, late season weed control is necessary to stop seedset.

Abstract Herbicide mineralization in the soil is affected by several factors, including the herbicide application history of the soil, soil moisture, and whether the herbicide is co-applied with another herbicide. The objective of this work was to evaluate S-metolachlor mineralization in the soil as affected by soil moisture content, history of herbicide application, and association with glyphosate. 14C-S-metolachlor mineralization increased with increasing soil moisture content. The average cumulative mineralization of S-metolachlor at 63 days of incubation was 0.03, 0.80, and 1.80% in air-dried, field capacity, and saturated soil, respectively. The mineralization rate of S-metolachlor was greater under saturated conditions and affected by the association with glyphosate. Greater mineralization of S-metolachlor occurred in cornfield soil with a history of S-metolachlor application. The average cumulative mineralization was 0.24% in cornfield and 0.89% in non-cultivated area. We can conclude that the higher the soil moisture content the higher S-metolachlor mineralization and that the mixture of this herbicide with glyphosate increased its degradation compared to the application of the herbicide alone. While there is evidence suggesting enhanced degradation of S-metolachlor in soil previously subjected to corn cultivation and S-metolachlor application, drawing a definitive conclusion is challenging due to the influence of sorption observed in our dataset.

Abstract Background Weed control is essential in modern agriculture, though it has become more difficult with the emergence of resistance to most current herbicides and the slow registration process for new compounds. Objective Identify herbicide candidates using an innovative artificial intelligence algorithm that takes into effect biological parameters with the goal of reducing research and development time of new herbicides. Results We describe the discovery of 4-chloro-2-pentenamides as novel inhibitors of protoporphyrinogen oxidase (PPO), a known herbicide target site, by the Agrematch AI. Their herbicidal activity was evaluated in greenhouse assays, with the highest performing compound (AGR001) showing good activity pre-emergent at 150 g ha-1 and post emergent at 50 g ha-1 on the troublesome weed Palmer amaranth (Amaranthus palmeri). A lack of activity is reported on PPO resistant Palmer amaranth carrying the glycine 210 deletion (ΔG210) mutation. Conclusions The mode of action of 4-chloro-2-pentenamides was confirmed by the herbicide-dependent accumulation of protoporphyrin IX, subsequent light-dependent loss of membrane integrity, and direct in vitro inhibition of PPO. Modeling of these inhibitors’ docking in the active site of PPO shows that their flexible side chains can accommodate several binding poses in the catalytic domain.

Background Eucalyptus is the primary cultivated wood species in Brazil, covering 7.5 million hectares. Weed competition in eucalyptus plantations reduces yield and increases operational costs. FuturaGene/Suzano has developed genetically modified (GM) eucalyptus varieties with glyphosate herbicide tolerance (HT) as a modern tool for improving weed management practices in plantations. The first event received regulatory approval for commercial deployment in 2021. However, the introgression of a new GM trait into eucalyptus, a non-isogenic species, cannot be achieved through selfing or backcrossing. To overcome this limitation and expedite the introgression of HT into the breeding population, multiple GM events were generated, in various genetic backgrounds and genomic locations, enabling simultaneous crossing with numerous elite parents. Objective To characterize the newly developed HT GM eucalyptus events and assess their safety for the environment and wood production. Methods HT GM eucalyptus events were subjected to genome sequencing and glyphosate tolerance testing. Biosafety analyses and environmental impact assessments were conducted through field trials in various eucalyptus cultivation regions, comparing the HT GM eucalyptus with conventional clones. Results The new events proved highly tolerant to glyphosate and displayed different genomic insertion sites. No adverse effects on non-target organisms were observed, and there were no significant differences in the soil microbiota or decomposition profile.Conclusions: The HT GM events have been proven to be safe, posing a low risk to the environment, humans, and animals. Consequently, these HT GM eucalyptus varieties can be confidently utilized for wood production.

Abstract Glyphosate-resistant palmer amaranth, Amaranthus palmeri, a difficult to control weed with aggressive growth, capable of causing large yield losses in annual crops, was identified in Brazil, in the state of Mato Grosso, in 2015. After notification, an epidemiological survey was carried out to identify the place of entry and area of dispersion. Containment and eradication measures were quickly established by state and federal phytosanitary authorities through legislative measures. After identification, it was classified as a quarantine weed under official control. The Palmer amaranth Containment and Eradication Committee was established in order to support the phytosanitary defense agencies in the actions to combat the weed. State agricultural inspectors were trained to identify the species and survey the State. Actions aimed at the farmers were also carried out, highlighting the importance of identification, control and awareness. The weed was found in six municipalities in 10 farms in Mato Grosso. The importation of a used cotton harvester from the United States of America and its internal transit were found to be the main route of entry and spread of the weed. The weed spread to the State of Mato Grosso do Sul, in 2022 and was detected in two municipalities and six properties. A detailed survey is on progress. It is necessary to understand movement routes and establish measures to contain it. Effective measures regarding the importation and cleaning of used machinery needs to be adopted to avoid weed seed dispersal, and Federal legislation is needed to contain and eradicate the weed.

Abstract Background Amaranthus palmeri is an economically important plant species worldwide. The rapid growth and competitive potential of crops make A. palmeri a major problem. Studies on the dissemination potential of this weed in Brazil and worldwide are necessary to identify the regions with high climatic potential. Similarly, we analyzed the behavior of the species in the face of predicted climate change. Studies of this type can be performed using ecological niche modeling. Objective This work aimed to determine areas with climatic suitability for A. palmeri in the present and future climates in Brazil and globally. Methods We projected the potential distribution of A. palmeri based on the environmental requirements and stress parameters that limit this species in Brazil. Results For the current climate, our model identified regions with favorable climatic suitability for A. palmeri on most continents. The results showed that the suitability of A. palmeri in the Brazilian territory will decrease owing to predicted climate change. The future model highlighted decreases in the suitable northern, northeastern, and midwestern areas. An annual study of the occurrence of A. palmeri using the weekly growth index predicted by the model showed great potential for the species throughout the year, with a decrease in the driest months (July to August), indicating the preference of the species for moist soils. Tropical and subtropical zones are currently experiencing a reduction in suitable areas because of climate change in northeastern Brazil and western Australia. Temperate zone sites have potential areas of expansion for A. palmeri (northern USA, Russia, and China) under climate change. Conclusions Based on the results of this study, management strategies should be planned to contain the global spread of A. palmeri.