Metabolomic Analysis of Skin Malodor-Associated Compounds and Structure-based Prediction of Acetolactate Synthase Selective Sulfonylurea Inhibitors

Bromhidrosis is characterized as a chronic condition related to malodor from the skin. The underlying etiology is from bacterial decompositions of glandular secretion products. However, specific pathways and metabolites for the disease are yet to be investigated. Here, twenty-eight metabolites, including fifteen major sweat constituents and thirteen compounds emitted from malodor-producing skin bacteria, were subjected to the metabometric analysis using Metaboanalyst. Different pathways in the butanoate metabolism revealed that acetolactate synthase (ALS) in skin Staphylococcus epidermidis (S. epidermidis) bacteria are catalyzing pyruvate to several malodor compounds like diacetyl. In the docking studies of the sulfonylurea-ALS interaction, five selected sulfonylureas, which originally were developed for the treatment of diabetes mellitus type 2, showed different binding free energies (ΔG) from chlorimuron ethyl - a well-known ALS sulfonylurea inhibitor. Amongst five sulfonylureas, gliquidone and glisoxepide were found to have free energy differences that were lower than or equal to chlorimuron ethyl, revealing their high affinities to ALS. In the future, further investigations of gliquidone and glisoxepide against ALS in skin bacteria would be crucial in repurposing these two sulfonylureas as new anti-bromhidrosis drugs.

In Vitro Evaluation of Herbicides on Beneficial and Pathogenic Microorganisms

An experiment was conducted in the laboratory to evaluate the effect of herbicides on beneficial and pathogenic microorganisms. Eighteen treatments included six herbicides at three different doses viz., cyhalofop-butyl (80, 160 and 240 ppm), cyhalofop-butyl + penoxsulam (150, 300 and 450 ppm), bispyribac-sodium (25, 50 and 75 ppm), fenoxaprop-p-ethyl (60, 12 and 180 ppm), carfentrazone-ethyl (20, 40 and 60 ppm) and chlorimuron-ethyl + metsulfuron-methyl (4, 8 and 12 ppm) evaluated on beneficial microbial bioagents (Trichoderma viride and Pseudomonas fluorescens) and pathogenic microorganisms (Rhizoctonia solani, Pyricularia oryzae and Xanthomonas oryzae pv. oryzae). Results revealed that bispyribac-sodium and cyhalofop-butyl + penoxsulam had greatest inhibitory effect on pathogenic microorganisms Rhizoctonia solani (47.76 and 54.40%) and Pyricularia oryzae (49.07 and 61.12%), but showed no effect on Xanthomonasoryzaepv. oryzae, and were less harmful to biocontrol agents Trichoderma viride and Pseudomonas fluorescens at recommended doses, which were effective in control of broad spectrum of weed flora in rice ecosystem.

Experimental design optimization of RP-HPLC method for simultaneous estimation of metsulfuron-methyl, chlorantraniliprole and chlorimuron-ethyl residues in stems of Oryza sativa

Background The study aims to develop a chemometrics optimized D-optimal mixture design approach assisted RP- HPLC method for the determination of pesticide residues of metsulfuron-methyl, chlorantraniliprole, and chlorimuron-ethyl in the stems of Oryza sativa. Chromatographic separation was achieved on a C18 column using a mobile phase consisting of a pH 3.5 phosphate buffer and acetonitrile in the ratio 85:15. Results The optimized HPLC method gave a sharp resolution of metsulfuron-methyl, chlorantraniliprole and chlorimuron-ethyl at a retention time of 2.599 min, 3.805 min and 4.661 min receptively. Linearity was observed in the range 100‒500 µg/mL for metsulfuron-methyl (r2 = 0.999), 4‒20 µg/mL for chlorantraniliprole (r2 = 0.999) and 100‒500 µg/mL for chlorimuron-ethyl (r2 = 0.999). The developed method was validated as per ICH guidelines. Conclusion The proposed chemometrics optimized RP-HPLC method was found to be successful in the resolution of pesticide residues in the stems of O. sativa. The developed method can be applied to routine quantification of metsulfuron-methyl, chlorantraniliprole and chlorimuron-ethyl.

Evaluating Efficacy of Preemergence Soybean Herbicides Using Field Treated Soil in Greenhouse Bioassays

Amidst widespread occurrence of herbicide-resistant weeds in the United States, the use of PRE herbicides and cover crops have resurged once again as important strategies for weed management in cropping systems. The objective of this experiment was to evaluate the length of soil residual weed control from PRE soybean herbicides and the detrimental impact of these herbicides on cover crop species using field treated soil in greenhouse bioassays. Greenhouse bioassays were conducted using soil from field experiments conducted in 2018 and 2019 at Arlington and Lancaster, WI. PRE herbicides consisted of imazethapyr, chlorimuron-ethyl, and cloransulam-methyl (acetolactate synthase [ALS]-inhibitors), metribuzin (photosystem II [PSII]-inhibitor), sulfentrazone, flumioxazin, and saflufenacil (protoporphyrinogen oxidase [PPO]-inhibitors), acetochlor, S-metolachlor, dimethenamid-P, and pyroxasulfone (very long-chain fatty acid [VLCFA]-inhibitors), and a nontreated control. Greenhouse bioassays were conducted using soil (0-10 cm depth) sampled at 0, 10, 20, 30, 40 and 50 d after treatment (DAT). Palmer amaranth and giant foxtail (weeds), and radish and cereal rye (cover crops) were used as bioindicators of herbicide levels in the soil. Bioassay results showed extended soil residual control of Palmer amaranth with sulfentrazone and pyroxasulfone; extended residual control of giant foxtail was observed with pyroxasulfone and S-metolachlor. Chlorimuron-ethyl and metribuzin were the most injurious herbicides to radish and cereal rye shortly after application, respectively, but minimal injury was observed from soil samples collected 50 DAT indicating the use of PRE and fall seeded cover crops in southern Wisconsin can be compatible. These results can support growers and practitioners with selection of effective PRE herbicides for Palmer amaranth and giant foxtail control and reduced impact on fall seeded radish and cereal rye cover crops altogether leading to more effective, diverse and sustainable weed management programs.

Multiple herbicide-resistant Palmer amaranth (Amaranthus palmeri) in Connecticut: confirmation and response to POST herbicides

Palmer amaranth is the latest pigweed species documented in Connecticut; it was identified there in 2019. In a single-dose experiment, the Connecticut Palmer amaranth biotype survived the field-use rates of glyphosate (840 g ae ha−1) and imazaquin (137 g ai ha−1) herbicides applied separately. Additional experiments were conducted to (1) determine the level of resistance to glyphosate and acetolactate synthase (ALS) inhibitors in the Connecticut-resistant (CT-Res) biotype using whole-plant dose-response bioassays, and (2) evaluate the response of the CT-Res biotype to POST herbicides commonly used in Connecticut cropping systems. Based on the effective dose required for 90% control (ED90), the CT-Res biotype was 10-fold resistant to glyphosate when compared with the Kansas-susceptible (KS-Sus) biotype. Furthermore, the CT-Res biotype was highly resistant to ALS-inhibitor herbicides; only 18% control was achieved with 2,196 g ai ha−1 imazaquin. The CT-Res biotype was also cross-resistant to other ALS-inhibitor herbicides, including chlorimuron-ethyl (13.1 g ai ha−1), halosulfuron-methyl (70 g ai ha−1), and sulfometuron-methyl (392 g ai ha−1). The CT-Res Palmer amaranth was controlled 75% to 100% at 21 d after treatment (DAT) with POST applications of 2,4-D (386 g ae ha−1), carfentrazone-ethyl (34 g ai ha−1), clopyralid (280 g ae ha−1), dicamba (280 g ae ha−1), glufosinate (595 g ai ha−1), lactofen (220 g ai ha−1), oxyfluorfen (1,121g ai ha−1), and mesotrione (105 g ai ha−1) herbicides. Atrazine (2,240 g ai ha−1) controlled the CT-Res biotype only 52%, suggesting the biotype is resistant to this herbicide as well. Here we report the first case of Palmer amaranth from Connecticut with multiple resistance to glyphosate and ALS inhibitors. Growers should proactively use all available weed control tactics, including the use of effective PRE and alternative POST herbicides (tested in this study), for effective control of the CT-Res biotype.

MANAGEMENT OF GLYPHOSATE-RESISTANT HAIRY FLEABANE AND CONTRIBUTION OF THE PHYSIOLOGICAL POTENTIAL OF SEEDS TO RESISTANCE

ABSTRACT Hairy fleabane (Conyza bonariensis L.) is a major weed of the conventional crop systems. Therefore, the objectives of the present study were to assess the responses of glyphosate-susceptible (S) and -resistant (R) C. bonariensis at various developmental stages and evaluate the physiological potential of seeds to propose alternative herbicides for the control of this weed. Two experiments were performed in replicates. The first experiment was performed in a greenhouse, arranged in a 2 x 3 x 10 factorial design. Specifically, two hairy fleabane biotypes (S and R) at different developmental stages (I, II, and III) were subjected to various treatments (glyphosate, chlorimuron-ethyl, metsulfuron-methyl, diclosulam, ammonium glufosinate, paraquat, paraquat+diuron, diquat, 2,4-D, and control). Percentage control was evaluated at 7, 14, 21, and 28 days after the application of the treatments (DAT), and shoot dry mass (SDM) was measured at 28 DAT. The second experiment was performed in a laboratory to evaluate the physiological potential of seeds based on the weight of 1000 seeds (TSW); shoot length (SL), radicle length (RL), total length (TL), fresh seedling mass (FSM), dry seedling mass (DSM), accelerated aging (AA) and cold test (CT), and germination (G) in response to cold and accelerated aging. The alternative herbicides tested effectively controlled biotype R up to the stage -I. Seeds of biotype R showed higher physiological potential in terms of all analyzed variables and exhibited greater tolerance to adverse conditions during seedling establishment. Therefore, strategies for the management of glyphosate-resistant hairy fleabane should aim at preventing new seed production.

Selectivity of Pre and Postemergence Herbicides in Single or Combined Applications in Castor Crop

One of the main challenges in castor crop (Ricinus communis L.) production is efficient weed management mainly due to limited options of selective herbicides. This study evaluated the selectivity of herbicides applied alone or in combination in pre- and postemergence applications in castor crop. Two field experiments were carried out under irrigation conditions in a semi-arid region of Northeast Brazil. It was found that the visual symptoms of phytointoxication of the herbicides used on castor were mild in both experiments. Consequently, there were no significant interferences on plant height, number of racemes, and grain (seed) yield. Pre-emergence applications (g ha−1) of trifluralin (1800), pendimethalin (1500), clomazone (750), clomazone + trifluralin (750 + 1800), and clomazone + pendimethalin (750 + 1500) followed by chlorimuron-ethyl in postemergence (15 g ha−1) are selective to castor. The application (g ha−1) of pendimethalin + clomazone (1000 + 500) in pre-emergence, associated with chlorimuron-ethyl (10 and 15), metamitron (2800 and 4200), ethoxysulfuron (60 and 80), or halosulfuron-methyl (75 and 112.5) in one or two applications in postemergence, as single or split applications, in an interval of 14 days, are selective to castor crop.

MANEJO DE Amaranthus hybridus EM ÁREA DE INTEGRAÇÃO LAVOURA-PECUÁRIA NA REGIÃO SUL DO RIO GRANDE DO SUL

A área cultivada com soja aumentou no Brasil nos últimos anos, assim como sua produção total. No Rio Grande do Sul (RS) o cultivo da leguminosa também mostra crescimento, sendo utilizado na sucessão à pecuária de corte no período frio, modelo de produção que contribui para melhor utilização das áreas durante os 12 meses do ano, contribuindo assim para o incremento da renda do produtor, bem como, quando bem manejado, colaborar no manejo integrado de plantas daninhas. Apesar disso, a presença de plantas daninhas dicotiledôneas de difícil controle como Amaranthus hybridus em lavouras de soja do RS vêm aumentando. Assim, o objetivo deste estudo foi avaliar a eficiência de herbicidas pré- e pós-emergentes, e de diferentes programas de manejo para controle de populações de Amaranthus hybridus. O estudo foi composto por quatro experimentos, dois sob condições controladas em casa de vegetação e dois a campo, em uma propriedade rural no município de Cerrito, RS, que integra a produção de soja com pecuária de corte. Os experimentos evidenciaram que alguns biótipos são tolerantes ao glyphosate e aos herbicidas inibidores de ALS (imazethapyr e chlorimuron-ethyl), e que a utilização dos herbicidas pré-emergentes imazethapyr + flumioxazin, metribuzin, s-metolachlor e sulfentrazone + diuron contribui para o manejo destes biótipos. Verificou-se também que a dessecação do azevém e sua complementação com herbicidas de contato e o uso de pré-emergentes são fatores determinantes para o controle de A. hybridus. Ainda, os resultados apontam que em condições de déficit hídrico, a presença de palha prejudica a eficiência de alguns herbicidas pré-emergentes.

Evaluation of intoxication caused by post-emerging herbicides in cassava culture in two times of application

This study aimed to evaluate the selectivity of post-emergent herbicides in cassava in two application times. The experiments were carried out in a greenhouse at the Federal University of Tocantins - UFT, Campus Gurupi. The experimental designed was completely randomized arranged in a 5x2 factorial scheme, composed by the combination of 5 herbicide molecules with different mechanisms of action (mesotrione, carfentrazone-ethyl, chlorimuron-ethyl, nicosulfuron and imazethapyr) applied in two seasons, 30 and 45 days after emergence (DAE), with four repetitions. The cultivar used was “Cacau melhorada”. The visual intoxication of the culture was evaluated. The results obtained were subjected to analysis of variance, by the F test, with the averages analyzed statistically by the LSD mean test, at 5% probability. The treatments based on mesotrione, and chlorimuron-ethyl were not toxic to the culture, promoting results similar to those observed for control. There were differences in the level of tolerance to the studied herbicides, between the times of application of the herbicides.

Control of glyphosate-resistant horseweed and giant ragweed in soybean with halauxifen-methyl applied preplant

Horseweed and giant ragweed are competitive, annual weeds that can negatively impact crop yield. Biotypes of glyphosate-resistant (GR) giant ragweed and horseweed were first reported in 2008 and 2010 in Ontario, respectively. GR horseweed has spread throughout the southern portion of the province. The presence of GR biotypes poses new challenges for soybean producers in Canada and the United States. Halauxifen-methyl is a recently registered selective herbicide for broadleaf weeds, for preplant use in corn and soybean. There is limited literature on the efficacy of halauxifen-methyl on GR horseweed and giant ragweed when combined with currently registered products in Canada. The purpose of the experiment was to determine the effectiveness of halauxifen-methyl applied alone, and tank-mixed for GR giant ragweed and GR horseweed control in glyphosate and dicamba-resistant (GDR) soybean in southwestern Ontario. Six field experiments were conducted separately for each weed species over 2018 and 2019. Halauxifen-methyl applied alone controlled GR horseweed 72% at 8 weeks after application (WAA). Control was improved to >91% when halauxifen-methyl applied in combination with metribuzin, saflufenacil, chlorimuron-ethyl + metribuzin and saflufenacil + metribuzin. At 8 WAA, halauxifen-methyl controlled GR giant ragweed 11%; glyphosate/2,4-D choline, glyphosate/dicamba, glyphosate/2,4-D choline + halauxifen-methyl and glyphosate/dicamba + halauxifen-methyl controlled GR giant ragweed 76 to 88%. This study concluded that halauxifen-methyl applied preplant in a tank-mixture can provide effective control of GR giant ragweed and horseweed in GDR soybean.