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Abiotic stresses such as herbicides can affect plant growth and yield. Using herbicide-resistant plant growth-promoting bacteria is a new approach to mitigate these side effects. This study was conducted to evaluate the effect of three native plant growth-promoting bacteria isolated from the Medicago sativa rhizosphere, including Serratia rubidaea (A) and Pseudomonas putida (B), Serratia sp. (C) plus Synorhizobium meliloti (R) and their combinations (AB, AC, BC, ABC, AR, BR, CR, ABR, ACR, BCR, and ABCR) on microbial population, plant biomass, antioxidant enzymes (CAT, APX, and GPX) activities, and hydrogen peroxide and malondialdehyde contents at the presence and absence of imazethapyr herbicide. The results indicated that herbicide application decreased plant biomass but increased microbial population, antioxidant enzymes activities, and the concentrations of hydrogen peroxide and malondialdehyde of all inoculated and non-inoculated plants. Bacterial inoculation in most cases increased microbial population, plant biomass, and antioxidant activities. These increases were more evident under herbicide application. The highest increase in these attributes was achieved by AB, AR, and ABR inoculums in the presence and absence of the herbicide. The microbial population, plant biomass and antioxidant activities were decreased under BC, CR, BCR, and ABCR inoculations. It can be concluded that in addition to growth promotion, these bacteria increase resistance against herbicide stress by controlling free-radical induced oxidative stress and lipid peroxidation through antioxidant enzymes. These findings create new visions in biofertilizer preparation for reducing environmental stresses.

Weeds are one of the greatest threats to faba bean (Vicia faba L.) production and herbicide application is known to be the most efficient weed control method. However, the susceptibility of the current cultivars to post emergence herbicide applications impose a limitation for weed control in faba bean. Therefore, the deployment of postemergence herbicide tolerance is desirable in faba bean. To address this, a set of 130 faba bean accessions were screened for their response to the recommended dosages of two herbicides, metribuzin at 250 g a.i. ha−1 and imazethapyr at 75 g a.i. ha−1 at Marchouch and Terbol stations during four seasons between 2014 and 2018. The herbicide damage score along with other phenological and yield related traits were recorded and analyzed to evaluate the effects of post emergence herbicide application on the tested accessions and to select the herbicide tolerant ones. Tolerance to metribuzin and imazethapyr in eight faba bean accessions was confirmed as no significant reduction in grain yield resulted from the herbicide application. Moreover, in the aim to identify superior and broad adapted herbicide tolerant faba bean genotypes and to identify the most discriminating environments for herbicide screening, 37 accessions with different levels of tolerance to the recommended dosages of metribuzin and imazethapyr were selected to further evaluate the performance and stability of their plant height and grain yield across different environments (location x season x herbicide treatment). Data collected at Marchouch and Terbol during four seasons between 2014 and 2019 were used and the evaluation was based on the following stability parameters: cultivar superiority, static stability, Wricke’s eco-valence and Finlay and Wilkinson’s regression model. Differences observed in the genotypes ranking suggest that the evaluation of performance and stability of herbicide tolerant faba beans should be based on a combination of stability parameters. Genotype * environment biplot analysis indicated that the environments representing the metribuzin treatment at Marchouch 2014–2015 and the non-treated treatment at Terbol 2018–2019 are the ideal environments for evaluating faba bean genotypes. Biplots showed also that the metribuzin and imazethapyr tolerant accession IG12983 is the ideal genotype as he showed good and stable plant height and grain yield performance across the environments. Finally, to identify molecular markers associated with key genes imparting tolerance to herbicides the same set of accessions phenotyped before was genotyped using genotyping by sequencing (GBS). The GBS yield 10,794 high quality single nucleotide polymorphisms (SNPs). 10 and 14 SNPs highly associated with phenological and yield related traits under herbicide treatments were identified after conducting Single-trait and Multi-trait Genome Wide Association Studies (GWAS) respectively. Genomic sequences containing herbicide tolerance associated SNPs were aligned against the NCBI database using BLASTX tool and default parameters to annotate candidate genes underlying the causal variants. SNPs from acidic endochitinase, LRR receptor-like serine/threonine-protein kinase RCH1, probable serine/threonine-protein kinase NAK, malate dehydrogenase, photosystem I core protein PsaA and MYB-related protein P-like were significantly associated with herbicide tolerance traits. The identified SNPs will facilitate and fasten the efficient and effective development of herbicide tolerant cultivars and can be used for introgressing herbicide tolerance into desired agronomic background. Las malas hierbas se consideran como mayor amenaza para la producción de las habas (Vicia faba L.) ya que no se dispone de métodos efectivos de control adecuados particularmente en el estado de postemergencia. En un intento de mejorar la tolerancia a los herbicidas de postemergencia más comunes, se evaluó durante cuatro años la respuesta de una colección de 130 accesiones de habas a las dosis recomendadas de metribuzin (250 g i.a. ha−1) e imazetapir (75 g i.a. ha−1) en condiciones de campo en las estaciones experimentales de Marchouch (Marruecos) y Terbol (Líbano). Estos trabajos han permitido confirmar la tolerancia de ocho accesiones a metribuzin y a imazetapir. Asimismo, se ha estudiado la estabilidad de componentes del rendimiento de 37 accesiones de habas con diferentes niveles de tolerancia a las dosis recomendadas de ambos herbicidas en diferentes ambientes (localidad x año x tratamiento con herbicida). Los resultados mostraron que la estabilidad de la respuesta en habas tolerantes a herbicidas se basa en una combinación de efectos. Los análisis de interacción Genotipo*Ambiente mostraron el tratamiento con metribuzin en Marchouch 2014-2015 y el control sin herbicida en Terbol 2018-2019 son los ideales para evaluar los genotipos de habas con tolerancia a herbicidas. La accesión IG12983 tolerante a ambos herbicidas mostró una altura de planta y rendimiento de grano altos y estables en todos los ambientes. Finalmente, la colección de habas fue genotipada por secuenciación (Genotyping by Sequencing “GBS”), resultando en la identificación de 10.794 polimorfismos de un solo nucleótido (SNP) de alta calidad. El análisis de asociación (Genome Wide Association “GWAS”) permitió la identificación de 10 y 14 SNP altamente asociados con tolerancia a los herbicidas, según se analizara por un solo o por múltiples caracteres, respectivamente. Las secuencias genómicas que contenían SNP asociados con la tolerancia a los herbicidas se alinearon con la base de datos del NCBI utilizando y la herramienta BLASTX y parámetros predeterminados para anotar los genes candidatos subyacentes a las variantes causales. Los SNP de la endoquitinasa ácida, la serina/treonina-proteína quinasa RCH1 similar al receptor LRR, la probable serina/treonina-proteína quinasa NAK, la malato deshidrogenasa, la proteína PsaA del núcleo del fotosistema I y la “MYB”- relacionada con proteína “P-like” se asociaron significativamente con los caracteres de a tolerancia a herbicidas. Estos SNP identificados permitirán acelerar el desarrollo eficiente y eficaz de cultivares tolerantes a herbicidas.

Assessing the adaptability and stability of herbicide-tolerant lentil accessions to two broad-spectrum post-emergence herbicides in multi-environment trials has become a must in a breeding program to improve its selection. The adaptability and stability of 42 herbicide-tolerant lentil accessions were investigated using five stability parameters under eight different environments. Significant Genotype–Environment (GE) interaction was found for days to flowering (DFLR), days to maturity (DMAT), and seed yield per plant (SY). The analyzed stability parameters such as Cultivar superiority, Finlay–Wilkinson, Shukla, Static Stability, and Wricke’s Ecovalence ranked the tested accessions differently, confirming the importance of using a combination of stability parameters when evaluating the performance of a group of accessions. GGE biplot of the SY trait accounted for 60.79% of sums of squares of the GE interaction and showed that cool and high rainfall environments are ideal for testing the agronomic performance of tolerant accessions. The GGE biplot of SY showed that IG4605(19), IG195(6), and IG156635(12) were specifically adapted to one mega environment, whereas IG70056(38) was identified as a superior line having a high and stable yield. These lines should be included in lentil crossing programs to develop herbicide-tolerant cultivars adapted to diverse environments.

Herbicide resistance is broadly recognized as the adaptive evolution of weed populations to the intense selection pressure imposed by the herbicide applications. Here, we tested whether transcriptional gene silencing (TGS) and RNA-directed DNA Methylation (RdDM) pathways modulate resistance to commonly applied herbicides. Using Arabidopsis thaliana wild-type plants exposed to sublethal doses of glyphosate, imazethapyr, and 2,4-D, we found a partial loss of TGS and increased susceptibility to herbicides in six out of 11 tested TGS/RdDM mutants. Mutation in REPRESSOR OF SILENCING 1 (ROS1), that plays an important role in DNA demethylation, leading to strongly increased susceptibility to all applied herbicides, and imazethapyr in particular. Transcriptomic analysis of the imazethapyr-treated wild type and ros1 plants revealed a relation of the herbicide upregulated genes to chemical stimulus, secondary metabolism, stress condition, flavonoid biosynthesis, and epigenetic processes. Hypersensitivity to imazethapyr of the flavonoid biosynthesis component TRANSPARENT TESTA 4 (TT4) mutant plants strongly suggests that ROS1-dependent accumulation of flavonoids is an important mechanism for herbicide stress response in A. thaliana. In summary, our study shows that herbicide treatment affects transcriptional gene silencing pathways and that misregulation of these pathways makes Arabidopsis plants more sensitive to herbicide treatment.

Los girasoles Imisun son cultivares resistentes a imidazolinonas en los cuales coexisten dos mecanismos de resistencia: (i) una mutación puntual en el sitio blanco del herbicida (resistencia relacionada al sitio de acción) y (ii) resistencia no relacionada al sitio de acción (NTSR). En la tecnología Imisun, NTSR podría estar relacionada con el metabolismo del herbicida y podría resultar de una sobreexpresión constitutiva de los genes detoxificadores, o inducida luego del tratamiento con herbicida. El objetivo de este trabajo fue caracterizar NTSR en girasoles Imisun en respuesta al tratamiento de imazetapir mediante RNA-seq, y determinar si estos mecanismos son constitutivo o inducidos por el herbicida. Las cipselas fueron germinadas en multimacetas, regadas por capilaridad y se mantuvieron en una cámara bajo condiciones controladas. Plantas de 7 días fueron tratadas con imazetapir 0 (control) y 1 μM por 12 h. Luego de la purificación del RNA de hoja, se construyeron bibliotecas de cDNA stranded y paired-end. La secuenciación se llevó a cabo en Illumina HiSeq2000. Se realizaron dos tipos de estrategias de mapeo local contra el transcriptoma de referencia HaT13l, incluyendo y filtrando multihits, respectivamente y se realizó el análisis de la expresión diferencial. Se identificaron 61 y 47 contigs (de acuerdo a la estrategia de mapeo) relacionados a metabolismo de xenobióticos: citocromos P450, transportadores ABC, glicosiltransferasas, UDPglucuronosil/glucosiltransferasas y glutatión S-transferasas. No se encontró expresión diferencial entre las plantas tratadas y sin tratar con imazetapir para ninguno de los contigs. La expresión de 17 contigs de interés fue validada mediante qRT-PCR. Estos resultados sugieren que mecanismos NTSR constitutivos estarían involucrados con la resistencia a imidazolinonas en girasol. Imisun sunflowers (Helianthus annuus L.) are imidazolinone-resistant cultivars in which the two mechanisms of herbicide resistance coexist: (i) mutation in herbicide target-site (target-site resistance) and (ii) non-target-site resistance (NTSR). In Imisun technology, NTSR could be related to herbicide metabolism and might occur as a result of a constitutive up-regulation of resistance genes, or it can appear only after herbicide treatment. The objective of this study was to characterize NTSR in Imisun sunflower in response to imazethapyr using RNA-Seq and to determine whether these mechanisms are constitutive or herbicide-induced. Cypsels were germinated in plastic pots, watered by capillarity and growth in chamber under controlled conditions. Seven-day-old plants were treated with 0 (control) and 1 μM imazethapyr for 12 h. After leaf RNA purification, stranded, paired-end cDNA libraries were constructed. Sequencing was performed with Illumina HiSeq2000. Local mapping, with and without multihits, was carried out over the reference transcriptome HaT13l and differential expression was analysed. Sixty one and 47 contigs (according to mapping strategy) related to xenobiotic metabolism were found: cytochromes P450s, ABC transporters, glycosyltransferases, UDPglucuronosyl/glucosyltransferases and glutathione S-transferases. None of these contigs showed differential expression between control and imazethapyr-treated plants. Seventeen interesting contigs were verified by qRT-PCR. These results suggest that constitutive NTSR mechanisms may account for imidazolinone resistance in Imisun sunflower. Fil: Gil, Mercedes. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Investigaciones en Ciencias Agrarias de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Instituto de Investigaciones en Ciencias Agrarias de Rosario; Argentina Fil: Vega Tessandori, María Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Investigaciones en Ciencias Agrarias de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Instituto de Investigaciones en Ciencias Agrarias de Rosario; Argentina Fil: Felitti, Silvina Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Investigaciones en Ciencias Agrarias de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Instituto de Investigaciones en Ciencias Agrarias de Rosario; Argentina Fil: Picardi, Liliana Amelia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Investigaciones en Ciencias Agrarias de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Instituto de Investigaciones en Ciencias Agrarias de Rosario; Argentina Fil: Balzergue, Sandrine. Institut National de la Recherche Agronomique; Francia. Centre National de la Recherche Scientifique; Francia Fil: Nestares, Graciela María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Investigaciones en Ciencias Agrarias de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Instituto de Investigaciones en Ciencias Agrarias de Rosario; Argentina

Imidazolinone resistance found in a wild sunflower (Helianthus annuus L.) population was successfully transferred to a cultivated inbred line developing ‘Imisun’ sunflowers. Genetic regulation of this trait has been reported to involve two genes: Imr1, an allelic variant of ahasl1 locus that codes for acetohydroxyacid synthase catalytic subunit, and the modifier Imr2, whose identity remains unknown, but it could be related to non-target-site resistance such as xenobiotic metabolism. The aim of the present study was to characterize the gene expression of resistant and susceptible sunflower lines in response to imazethapyr herbicide by complementary DNA amplified fragment-length polymorphism (cDNA-AFLP). Three assays were performed to determine (i) optimal herbicide treatment concentration, (ii) duration of herbicide treatment, and (iii) in vitro acetohydroxyacid synthase activity to assess enzyme inhibition levels. An important number of genes related to metabolism of xeno-biotics and stress was found: cytochrome P450 monooxygenases, UDP-glucuronosyl/UDP-glucosyltransferases, glycosyltransferases, and ATP-binding cassette transporters, among others. These results suggest that non-target-site resistance mechanisms may contribute to herbicide resistance in Imisun sunflower and could be related to the modifier gene Imr2. Using cDNA-AFLP, we were able to detect candidate detoxification-related genes potentially involved in imidazolinone resistance in sunflower. Fil: Gil, Mercedes. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Investigaciones en Ciencias Agrarias de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Instituto de Investigaciones en Ciencias Agrarias de Rosario; Argentina Fil: Ochogavía, Ana Claudia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Investigaciones en Ciencias Agrarias de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Instituto de Investigaciones en Ciencias Agrarias de Rosario; Argentina Fil: Vega, Tatiana Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Investigaciones en Ciencias Agrarias de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Instituto de Investigaciones en Ciencias Agrarias de Rosario; Argentina Fil: Felitti, Silvina Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Investigaciones en Ciencias Agrarias de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Instituto de Investigaciones en Ciencias Agrarias de Rosario; Argentina Fil: Nestares, Graciela María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Investigaciones en Ciencias Agrarias de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Instituto de Investigaciones en Ciencias Agrarias de Rosario; Argentina

Field experiments were conducted during two years at Srem region to investigate the influence of meteorological conditions, time and rate of application on soil persistence of imazethapyr in sandy loam type of soil. Imazethapyr was applied PRE- and POST-EM and in both cases in three application rates: 80, 120 and 160g a.i./ha. Soil samples were collected from the day of herbicide application in predetermined intervals up to one year after application and residual concentrations were determined with a white mustard root bioassay. Imazetapyr persistence was significantly influenced by meteorological conditions with average half-life being 6days longer in season with lower precipitation level. Time of application induced slower imazethapyr dissipation resulting in higher average t(1/2) (seven and nine days in first and second year of examination, respectively). Application rates had no consistent effect on imazethapyr persistence. Imazethapyr residue level one year after application caused no visible injuries on white mustard shoots, while root growth reduction ranged from 4.6 to 27.7%. Obtained residue levels were further compared with known data on crop sensitivity in order to assess possibility of crop injuries one year after imazethapyr application.

Silky windgrass is a serious weed in central and northern Europe. Its importance has escalated in recent years because of its growing resistance to acetolactate synthase (ALS)-inhibiting herbicides. This study investigated the resistance level for three herbicide sites of action in eight silky windgrass populations, collected in fields neighboring a field where iodosulfuron sodium salt–resistant silky windgrass had previously been found. Target site resistance (TSR) and non–target site resistance (NTSR) mechanisms were identified, and a spatial gradient distribution hypothesis of ALS resistance was tested. Populations showed large variations in ED50values to iodosulfuron, with resistance indices (RIs) ranging from 0.1 to 372. No cross-resistance was found to other herbicide groups with the same site of action as iodosulfuron. In contrast, resistance was observed to the acetyl-CoA carboxylase inhibitor, fenoxaprop ethyl ester (RI from 0.7 to 776), while the activity of prosulfocarb, an inhibitor of long-chain fatty-acid synthesis, was unaffected. Iodosulfuron-resistant phenotypes were associated with NTSR, while fenoxaprop ethyl ester resistance was caused by both NTSR and TSR (Ile-1781-Leu mutation). A large-scale trend in the spatial distribution of resistance to ALS indicated a decreasing resistance with increased distance from an epicenter. After finer-scale analysis, less than 0.05% of the residual variation could be attributed to spatial autocorrelation. The spatial resistance pattern was not correlated with the dominant wind direction, while there was a correlation between the resistant phenotype and type of crop. This study underlines that NTSR mechanisms do not always confer broad resistance to different herbicide subclasses and site of action, hence the complex relationship to resistant phenotype. NTSR mechanisms, in particular detoxification, were present at different levels for the herbicides tested in the silky windgrass populations of this study. The factors contributing to the spatial distribution of resistance remain elusive.

Studies of herbicide efficacy in the control of field dodder in alfalfa (glyphosate, propyzamide, and imazethapyr) and sugar beet (propyzamide) were conducted under controlled conditions. The herbicides were applied when alfalfa plants were 10-12 cm high and sugar beet plants in the 2-3 true leaf growth stage, with dodder plants fixed to the hosts. The trial included two controls: noninfested (N) alfalfa and sugar beet plants and alfalfa and sugar beet plants infested (Z) with field dodder, but with no herbicide application. The efficacy of herbicides in the control of field dodder was assessed in two ways: visually on a 0-100 scale (0 denoting no damage at all, and 100 denoting plant death), and by measuring the weight of fresh biomass. These parameters were recorded: prior to herbicide treatment (0 assessment), then 7, 14, 21, 28 and 35 days after the aplication (DAA). The results have shown that two glyphosate application rates (384 and 480 g ai ha-1) have demonstrated the highest efficacy of 95% and 97.5%, respectively. Both application rates of propyzamide (1500 and 2000 g ai ha-1) had weak efficacy (85% and 87%, respectively), while imazethapyr (150 g ai ha-1) was the weakest herbicide, with an 80% efficacy. Finally, two propyzamide application rates (1500 and 2000 g ai ha-1) in sugar beet have demonstrated the efficacy of 85% and 90%, respectively. Ispitivanje efikasnosti herbicida u suzbijanju viline kosice u lucerki (glifosat, propizamid i imazetapir) i u šećernoj repi (propizamid) rađeno je u ogledu u saksijama. Primena herbicida je obavljena kada su biljke lucerke bile visine 10-12 cm, a biljke šećerne repe u fazi dva razvijena lista i začetka trećeg, pri čemu je vilina kosica bila vezana za domaćina. Kontrolne varijante: zaražene biljke lucerke i šećerne repe (Z) i nezaražene biljke lucerke i šećerne repe (N) nisu tretirane. Vizuelna ocena efekata na vilinoj kosici, kao i merenje sveže mase lucerke i šećerne repe su obavljeni pre primene herbicida (0 ocena), potom, 7, 14, 21, 28 i 35 dana nakon primene herbicida. Vizuelna procena oštećenja biljaka viline kosice je iskazana skalom od 0 (nema oštećenja) do 100 (biljke potpuno propale). Kod lucerke je najbolju efikasnost ispoljio glifosat u obe primenjene količine (384 i 480 g a.s. ha-1) i to 95% odnosno 97,5%. Efikasnost koju je postigao propizamid u obe količine primene (1500 i 2000 g a.s. ha-1) je bila slabija (85%, odnosno 87%), dok je najslabiju efikasnost ispoljio imazetapir (150 g a.s. ha-1) i ona je iznosila 80%. Primena propizamida u količinima 1500 i 2000 g a.s. ha-1 kod šećerne repe je ispoljila efikasnost od 85%, odnosno 90%.

Several studies have expressed concerns about the effects of gene flow from transgenic herbicide‐resistant crops to their wild relatives, but no major problems have been observed. This review describes a case study in which what has been feared in transgenics regarding gene flow has actually changed biodiversity and people's lives. Nontransgenic imidazolinone‐resistant rice (IMI‐rice) cultivars increased the rice grain yield by 50% in southern Brazil. This increase was beneficial for life quality of the farmers and also improved the regional economy. However, weedy rice resistant to imidazolinone herbicides started to evolve three years after the first use of IMI‐rice cultivars. Population genetic studies indicate that the herbicide‐resistant weedy rice was mainly originated from gene flow from resistant cultivars and distributed by seed migration. The problems related with herbicide‐resistant weedy rice increased the production costs of rice that forced farmers to sell or rent their land. Gene flow from cultivated rice to weedy rice has proven to be a large agricultural, economic, and social constraint in the use of herbicide‐resistant technologies in rice. This problem must be taken into account for the development of new transgenic or nontransgenic rice technologies.

The rises of toxic effects caused by pesticides are of concern. However, Brazilian legislation still needs scientific subsides to improve the water quality requirements. This can be attributed in part to the few existing studies showing the occurrence and levels of multi-residue pesticides. Therefore, the objective of this study was to investigate the presence and the residue-levels of pesticides in surface, ground and drinking water of Tibagi River micro-basin in Paraná State, Brazil. Data obtained over a year for the physical-chemical parameters, screening and quantification, made by liquid chromatography-tandem mass spectrometry (LC-MS/MS), confirmed the contamination by several pesticides. Alarming concentrations of diuron and imazethapyr in a permanent preservation area and in groundwater were observed. The absence of legislation for most pesticides under study makes difficult the prohibition of their use and the control of their residue-levels on the environment. The results draw attention to further discussion and engagement around the pesticide regulations.

O presente experimento teve por objetivo avaliar a seletividade de herbicidas e o controle de plantas daninhas, na pós-emergência da cultura do feijoeiro. Foram testados os herbicidas cloransulam e imazethapyr, isoladamente e em associação com bentazon e comparados com uma testemunha capinada e uma infestada, nas cultivares de feijão Agronorte (Anfc9) e IPR Uirapuru. O experimento foi conduzido a campo, em delineamento de blocos casualizados, com quatro repetições. Foram analisadas: fitotoxidez, controle de plantas daninhas, altura de inserção de primeiro legume, número de legumes por planta, peso de mil grãos e produtividade. Cada cultivar possui nível de tolerância diferente aos herbicidas cloransulam e imazethapyr. A cultivar ANfc9 foi, em geral, mais tolerante aos herbicidas que a IPR Uirapuru. A adição de bentazon aos herbicidas cloransulam ou imazethapyr, diminui a fitotoxidez causada à cultura do feijão, cultivares Agronorte (Anfc9) e IPR Uirapuru e não altera o controle de plantas daninhas, demonstrando não haver antagonismo na mistura.

The resistance of barnyardgrass (Echinochloa crus-galli) to imidazolinone herbicides is a worldwide problem in paddy fields. A rapid diagnosis is required for the selection of adequate prevention and control practices. The objectives of this study were to develop expedite bioassays to identify the resistance to imidazolinone herbicides in barnyardgrass and to evaluate the efficacy of alternative herbicides for the post-emergence control of resistant biotypes. Three experiments were conducted to develop methods for diagnosis of resistance to imazethapyr and imazapyr + imazapic in barnyardgrass at the seed, seedling and tiller stages, and to carry out a pot experiment to determine the efficacy of six herbicides applied at post-emergence in 13 biotypes of barnyardgrass resistant to imidazolinones. The seed soaking bioassay was not able to differentiate the resistant and susceptible biotypes. The resistance of barnyardgrass to imidazolinones was effectively discriminated in the seedlings and tiller bioassays seven days after incubation at the concentrations of 0.001 and 0.0001 mM, respectively, for both imazethapyr and imazapyr + imazapic. The biotypes identified as resistant to imidazolinones showed different patterns of susceptibility to penoxsulam, bispyribac-sodium and pyrazosulfuron-ethyl, and were all controlled with profoxydim and cyhalofop-butyl. The seedling and tiller bioassays are effective in the diagnosis of barnyardgrass resistance to imidazolinone herbicides, providing an on-season opportunity to identify the need to use alternative herbicides to be applied at post-emergence for the control of the resistant biotypes. A resistência de capim-arroz (Echinochloa crus-galli) aos herbicidas imidazolinonas é um problema crescente na cultura do arroz em diversas regiões do mundo, sendo necessário o seu diagnóstico rápido para a determinação de práticas de prevenção e controle. Os objetivos deste trabalho foram desenvolver métodos de identificação expedita da resistência de biótipos de capim-arroz aos herbicidas imidazolinonas e avaliar a eficácia de herbicidas alternativos para o seu controle em pós-emergência. Para isso, foram conduzidos três experimentos visando o desenvolvimento de métodos de diagnóstico da resistência aos herbicidas imazethapyr e imazapyr + imazapic em plantas de capim-arroz nos estádios de semente, plântula e perfilhos, bem como um experimento para determinar a eficácia de seis herbicidas em pós-emergência no controle de 13 biótipos de capim-arroz resistentes às imidazolinonas. A resistência de capim-arroz a imidazolinonas foi discriminada de forma eficiente nos experimentos com plântulas e perfilhos aos sete dias após a incubação nas concentrações de 0,001 e 0,0001 mM, respectivamente, para os herbicidas imazethapyr e imazapyr + imazapic. Os biótipos identificados como resistentes a imidazolinonas apresentaram diferentes padrões de suscetibilidade aos herbicidas penoxsulam, bispyribac-sodium e pyrazosulfuron-ethyl e somente foram controlados de modo eficaz com os herbicidas profoxydim e cyhalofop-butyl. Os bioensaios de plântulas e perfilhos são eficientes para o diagnóstico de capim-arroz resistente a imidazolinonas na mesma safra de desenvolvimento da cultura do arroz e proporcionam a identificação da necessidade de uso de herbicidas alternativos a serem aplicados em pós-emergência para o controle de biótipos resistentes.

A similaridade botânica do capim-annoni com as espécies forrageiras nativas ou cultivadas dificultam o seu controle em pastagens naturais. O objetivo deste trabalho foi avaliar o efeito de associações entre herbicidas e protetores sobre o controle de capim-annoni e a seletividade em pastagem natural. Foram realizados dois experimentos a campo em área de pastagem natural típica do Bioma Pampa avaliando-se herbicidas aplicados em pré e pós-emergência. Outro experimento foi conduzido em casa de vegetação com as espécies capim-annoni e grama forquilha onde foram avaliados os herbicidas glufosinate-ammonium e imazethapyr. Em ambos os experimentos os herbicidas foram avaliados isolados ou em associação com os protetores anidrido naftálico, dietholate e fluxofenim. Os experimentos a campo demonstraram que os herbicidas aplicados em pré ou pós-emergência em interação com os protetores não proporcionaram controle satisfatório do capim-annoni e nem aumento da seletividade à pastagem natural. Por outro lado, o experimento em condições controladas indicou a ocorrência de sinergismo do herbicida glufosinate-ammonium em interação com os protetores anidrido naftálico, dietholate e fluxofenim sobre o capimannoni. As diferenças relacionadas a estádio de desenvolvimento e densidade de infestação estão relacionadas as variações das respostas nos estudos a campo e em condições controladas. A utilização de herbicidas em associações com protetores apresenta potencialidade de controle seletivo de capim-annoni quando aplicado em plantas em estádios iniciais de desenvolvimento. The botanical similarity of the invasive weed Eragrostis plana Nees (South African lovegrass) difficult its selective control in natural pastures. The aim of this study was to evaluate the effect of the association between herbicides and safeners on the control of E. plana and on the selectivity to the natural pastures. Two experiments were conducted at field conditions in area of natural grassland of the Biome Pampa where several herbicides were evaluated in pre and postemergence. A third experiment was carried out in greenhouse evaluating the herbicides glufosinate-ammonium and imazethapyr and the species E. plana and Paspalum notatum. In both experiments, the herbicides were evaluated isolated and in association with the safeners anhydride naphtalic, dietholate and fluxofenim. The field experiments indicated that the evaluated safeners did not increase E. plana control and native grassland selectively. The greenhouse experiment indicated the occurrence of synergism on E. plana for the herbicide glufosinate-ammonium in mixture with the safeners anhydride naphtalic, dietholate and fluxofenim. The different results in the field and greenhouse experiments are related to the plant stage and density. The use of herbicides in association with safeners indicated a potentiality for selective control of E. plana when applied to plants in the early stages of development.

The interaction between imazethapyr (IMA) and bovine serum albumin (BSA) was investigated by fluorescence spectroscopy. The Stern-Volmer quenching constant (K SV) at three temperatures was evaluated in order to determine the quenching mechanism. The dependence of fluorescence quenching on viscosity was also evaluated for this purpose. The results showed that IMA quenches the fluorescence intensity of BSA through a static quenching process. The values of the binding constant for the formed BSA-IMA complex and the number of binding sites were found to be 1.51×10 5 M -1 and 0.77, respectively, at room temperature. Based on the calculated thermodynamic parameters, the forces that dominate the binding process are hydrogen bonds and van der Waals forces, and the binding process is spontaneous and exothermic. The quenching of protein fluorescence by iodide ion was used to probe the accessibility of tryptophan residues in BSA and the change in accessibility induced by the presence of IMA. According to the obtained results, the BSA-IMA complex is formed in the site where the Trp-134 is located, causing it to become less exposed to the solvent. © 2012 Elsevier B.V. All rights reserved. Fil: Pacheco, Maria Emilia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Química; Argentina Fil: Bruzzone, Liliana. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Química; Argentina

O objetivo deste trabalho foi avaliar o efeito residual dos herbicidas imazaquin, imazethapyr e diclosulam aplicados na cultura da soja sobre o girassol em sucessão. Nas parcelas, foi semeado o girassol aos 60 e 90 dias após a aplicação (DAA) do imazaquin e do diclosulam e 45 e 75 DAA do imazethapyr. As subparcelas foram compostas pelos herbicidas imazaquin (150 g/ha), imazethapyr (70 g/ha) e diclosulam (33,6 g/ha) aplicados na cultura da soja, além da testemunha (sem aplicação). O girassol, semeado aos 90 e aos 75 dias após a aplicação do imazaquin e do imazethapyr na cultura da soja, respectivamente, não apresenta sintomas de fitotoxicidade. O diclosulam causa redução total do estande de girassol nas duas épocas de semeadura. A lesão causada pelos herbicidas ao girassol, observada na produtividade da cultura, é maior em ordem decrescente de fitotoxicidade: diclosulam > imazaquin > imazethapyr.

Broomrape is a severe problem in the continuous cropping of bidi tobacco in India. Fifteen herbicides were evaluated for postemergence control, at different dates and rates, in field experiments in Nipani, Karnataka State. The effects of the herbicides onOrobanchecontrol and growth and yield of tobacco were compared to the effects of handweeding and an untreated check. Following this screening experiment, four herbicides were selected for further testing. Glyphosate at 500 g ai/ha applied at 60 days after transplanting (DAT) and imazaquin at 10 g ai/ha applied at 30 DAT reduced the number of aboveground broomrape spikes by 75 to 80% and increased the tobacco yields by 80 to > 100% compared to the untreated plots. Imazethapyr and EPTC were found to be less effective for broomrape control, but they still led to substantially higher tobacco yield. None of the herbicide treatments resulted in yields higher than those in the hand-weeded plots. These plots probably did not yet reflect the potential yield of tobacco under broomrape-free conditions, due to nonemerged spikes. Toxicity to tobacco of all herbicides was higher for the higher rates tested. It was lowest with imazaquin.

Imazethapyr herbicide [5-ethyl-2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl) nicotinic acid] is widely used on agricultural field crops in Morocco. It is reported that soil properties largely enhance the sorption of the herbicide in soils, however understanding their impact in soils of Morocco is needed. The present article investigates the sorption behavior of imazethapyr herbicide toward six agricultural soils from Morocco in batch equilibrium experiments at pH 5 and evaluates the effect of the organic matter, the clay content, and the cation exchange capacity (CEC) on the sorption by applying simple and multiple linear regressions. Freundlich isotherm model described well the dynamic of imazethapyr sorption in all studied soils under the experimental conditions. The linear regressions showed significant differences between the soil properties and their impact on the sorption. While simple regression revealed strong positive correlations between the sorption and both the soil clay content ( R 2 = 0.91) and CEC ( R 2 = 0.92), the multiple regression revealed a noteworthy influence of soil organic matter when combined with clays. Our findings showed a weak adsorption of imazethapyr on the selected Moroccan soils, in addition to a potential role of clay minerals and CEC in the retention of the herbicide compared to the organic matter. The low adsorptive capacity of the Moroccan soils urges the necessity of minimizing herbicide application rates in agricultural regions to prevent environmental detrimental impacts.

SUMMARY The response of RIMI [imazethapyr-tolerant (T)] sunflower (Helianthus annuus L.) hybrid and the local imazethapyr-sensitive hybrid "Zoltan" (S) was investigated under controlled conditions. Hybrids grown in pots were treated post-emergence with imazethapyr at the two pairs of leaves stage. Visual injury evaluation and vegetative parameters were recorded. ALS (acetolactate synthase) enzyme activity was estimated in vivo 24 h after imazethapyr application. Tolerance level was determined based on the resistance ratio index (ED50 - herbicide dose causing 50% growth inhibition of T hybrid/ ED50 of S hybrid). Significant differences were noted between the hybrids in the in vivo ALS activity and vegetative parameters. Indexes of resistance ranged between 5 and 452 for vegetative parameters, whereas the index for ALS activity was 210. The data confirmed the high level of tolerance of the hybrid Rimi as compared with the hybrid Zoltan.

The objective of the study was to analyze the suspectibility of three different types of hybrid maize to carryover potential of imazethapyr. Herbicide toxicity was analyzed using the bioassay, by determining the inhibition of root and shoot lenght and fresh weight. In addition, using the bioassay imazethapyr persistence in the leached chernozem soil type was studied. The aim was to determine the residues of imazethapyr based on the most sensitive parameter tested with regard to rate and time of application. Herbicide degradation was monitored over a period of one year following application during two trial years. The hybrids tested showed a significant susceptibility to herbicide tested. The doses analyzed inhibited root lenght and fresh weight to a greater extent. Regression analysis was used to determine I50 values for the parameter tested, thus proving root fresh weight reduction to be the most susceptible and accuretly computed parameter. Hybrid ZPTC 125 was the most susceptible (with regard to the parameters tested) Higher herbicide doses and post-em treatment provoked slower degradation of imazethapyr as confirmed by calculated DT-50 values. Imazethapyr residues (applied at the rate of 80 and 120 g a.i./ha pre-emergence) provoked no damage to ground parts (in both trial years). Shoot growth and fresh weight were reduced by 10 % in the post-emergence treatment (which was more prominent in the first trial year). Root lenght and fresh weight inhibition was more prominent, especially with the application of higher doses even in post-emergence treatments (for the most susceptible hybrid a little bit less than 20 % and aprox. 30 % in the first and second trial year, respectively). U radu je ispitivana osetljivost tri hibrida kukuruza na imazetapir. Metodom biotesta utvrđivana je inhibicija dužine i sveže mase korena i izdanka, kao pokazatelj fitotoksičnosti herbicida. Osim navedenog, biotest metodom je praćena i degradacija imazetapira u zemljištu tipa degradirani černozem, da bi se, na osnovu prethodno određenog najosetljivijeg merenog paramétra utvrdio nivo ostataka godinu dana nakon primene, a u zavisnosti od količine i vremena primene. Ova ispitivanja vršena su tokom dve uzastopne godine. Ispitivani hibridi ispoljili su značajnu osetljivost, pri čemu je inhibicija dužine i sveže mase korena bila mnogo izraženija za sve ispitivane koncentracije. Regresionom analizom utvrđene su I5o vrednosti za sve merene parametre, koje su potvrdile da je redukcija sveže mase korena najosetljiviji i najprecizniji mereni parametar. Najveću osetljivost ispoljio je hibrid ZPTC 125. Ispitivanja perzistentnosti pokazala su da veća količina i kasnije vreme primene herbicida uslovljavaju nešto sporiju degradaciju, a što je potvrđeno izračunatim DT-50 vrednostima. Godinu dana nakon primene ostaci imazetapira (primenjenog u količini od 80 i 120 g a.m./ha, nisu izazvali oštećenja nadzemnog dela (u obe godine ispitivanja). U post-em tretmanu redukcije rasta i sveže mase izdanka bile su do 10% (i izraženije u prvoj godini). Inhibicije dužine i sveže mase korena bile su izraženije, i uvek veće pri većoj količini primene i u post-em tretmanu, tako da su za najosetljiviji hibrid iznosile nešto manje od 20 % u prvoj, odnosno približno 30 % u drugoj godini ispitivanja.

Trials were conducted during 2000 and 2001 to determine efficacy of new herbicide azafenidin (Evolus 80WG) and imidazolinone herbicides imazamox (Bolero), imazamox + imazapyr (Euro-Lightning), imazamox + pendimethalin (Escort) in weed control in imidazolinone-tolerant sunflower. Mixtures with azafenidin provided better control of Datura stramonium than other herbicide mixtures of standard herbicides. Imidazolinone herbicides in imidazolinone- tolerant sunflower provided successful control of Abutilon theophrasti, Ambrosia artemisiifolia, Xanthium strumarium, Datura stramonium, a number of narrow-leaved weeds, and Orobanche cumana. Tokom 2000. i 2001. godine ispitivane su nove mogućnosti hemijskog suzbijanja korova u suncokretu, uključujući novi herbicid azafenidin (Evolus 80WG) i novu tehnologiju suzbijanja korova u suncokretu tolerantnom prema imidazolinonima. Ovo podrazumeva zajedničko korišćenje tolerantnog suncokreta prema herbicidima iz grupe imidazolinona i herbicida imazamoks (Bolero) i njegovih kombinacija sa pendimetalinom (Escort) i imazapirom (Euro-Lightning). Kombinacije sa preparatom Evolus 80WG ostvarile su bolju efikasnost u suzbijanju Datura stramonium. Dobijeni rezultati pokazuju napredak u suzbijanju ekonomski najznačajnijih korova u suncokretu, a posebno Abutilon theophrasti, Ambrosia artemisiifolia, Xanthium strumarium i Datura stramonium primenom herbicida iz grupe imidazolinona.

16 pages, 10 figures, 23 references., Adsorption of the imidazolinone herbicides imazapyr, imazethapyr and imazaquin was studied on two binary systems (ferrihydrite-humic acid) prepared by treating ferrihydrite (Fh) immediately after its precipitation with a soil humic acid (HA) at different loadings (4% and 8% HA content), and on a blank ferrihydrite sample prepared in the same way, but without HA addition. Imidazolinone adsorption on pure Fh and on the 4% Fh-HA decreased with increasing of the herbicide hydrophobicity (imazaquin imazethapyr imazapyr), whereas on the 8% Fh-HA system the order of adsorption was nearly the same, indicating that higher amounts of HA on Fh increase the hydrophobicity of the surface and thus increases its affinity for the herbicides, specially for imazaquin. Adsorption was also enhanced by low pH values and slight changes in pH enhanced the contribution of each component in adsorption. Both the nature of the surface exposed and its ability to interact with herbicides are greatly altered by the mutual interaction of Fh and HA. The results show that albeit artificial polyphasic associations are more representative of the real situation than single model components and are thus better indicators of the behaviour of a given herbicide in the soil.

8 pages, 2 tables, 2 figures, [14C]-Imazethapyr was applied as a seed treatment and at plant pre-emergence and post-emergence to peas (Pisum sativum L.) parasitized by Orobanche crenata Forsk. Herbicide uptake increased with time regardless of the application method. Uptake reached about 98%, 89%, 81% and 94% of the total herbicide applied for the seed coating, seed soaking, pre-emergence and post-emergence treatments respectively. Herbicide translocation within the host plants consistently differed between O. crenata-infected and non-infected plants. High levels of 14C activity were accumulated by parasitic plants from the host. In non-infected pea plants, pods were stronger sinks for imazethapyr than the other parts of the plant, regardless of the application method. The herbicide distribution in the pea plant: O. crenata complex showed the same pattern regardless of the application methods. However, accumulation of radioactivity in the parasite was lower with pre-emergence and post-emergence application than with the seed treatments. In addition, radioactivity concentration in O. crenata plants was slightly higher when [14C]-imazethapyr was applied to pea seeds by coating than by soaking.

A contaminação de águas subsuperficiais por agrotóxicos decorre principalmente da lixiviação de seus resíduos. Neste trabalho, estudou-se a lixiviação dos herbicidas imazamox e imazethapyr por meio de bioensaio. Areia lavada e quatro tipos de solo foram colocados em tubos de PVC em posição vertical que, após a aplicação dos herbicidas, receberam lâmina d’água de 60 mm. O delineamento experimental foi o de blocos ao acaso, com quatro repetições e com os tratamentos dispostos no esquema fatorial 2x5. Em cada coluna de solo, coletou-se a solução lixiviada que foi transferida para vasos contendo areia lavada, especificando-se o tratamento recebido. Nos vasos com a solução lixiviada, semeou-se sorgo; aos 17 dias, coletaram-se as partes aérea e do sistema radicular das plantas de sorgo, que foram secadas e analisadas estatisticamente. Nas doses testadas, o imazamox mostrou-se menos lixiviável que o imazethapyr. Ao estudar a lixiviação nos diversos tipos de solo, não se verificou diferença entre eles no que se refere ao peso da matéria seca da parte aérea das plantas, indicando que os solos não influenciaram no comportamento dos herbicidas estudados. PALAVRAS-CHAVE: Imazamox; imazethapyr; lixiviação; bioensaio. The lixiviation of herbicides is the most common cause of contamination of subsuperficial water. The objective of this paper was to study the lixiviation of the herbicides imazamox and imazethapyr by means of bioessay. The herbicides were applied to several types of soil into PVC tubes, followed by the addition of 60 mm of water. In each column of soil, leached material was collected and transferred to vases filled with washed sand. Sorghum was sowed in these vases. After seventeen days, the aerial parts and the roots were collected, dried and submitted to a statistic investigation. The lixiviation of imazamox was smaller than that of imazethapyr. As far as types of soil were concerned, there was no difference among them concerning to dry matter weight of the aerial parts. KEY-WORDS: Imazamox; imazethapyr; lixiviation; bioessay.

O objetivo do presente trabalho foi o de avaliar os efeitos da utilização de glyphosate e herbicidas imidazolinonas, em aplicações isoladas ou associadas, sobre o controle de arroz-vermelho (Oryza sativa) e produtividade de grãos de arroz Clearfield®. O experimento foi conduzido a campo na safra 2007/08, em Cachoeirinha, RS, Brasil, com delineamento em blocos ao acaso e tratamentos dispostos em arranjo fatorial (2x6), usando-se quatro repetições. O fator A constou de dois níveis do herbicida glyphosate, aplicados no subperíodo semeadura-emergência da cultura por ocasião do início da emissão do coleóptilo do arroz (ponto de agulha); o fator B constou de seis tratamentos com imazethapyr+imazapic, aplicados em associação ao glyphosate ou quando a cultura atingiu o estádio de três folhas expandidas. As três variáveis explicativas analisadas foram a população de plantas de arroz e arroz-vermelho, a eficácia do controle de arroz-vermelho e a produtividade de grãos da cultura. O uso de glyphosate no ponto de agulha reduziu em 75% a população do arroz-vermelho e aumentou em 40% a produtividade de grãos de arroz, em relação à testemunha. O uso isolado de herbicidas imidazolinonas e sua associação com o dessecante proporcionou controle eficaz do arroz-vermelho e incrementou a produtividade de grãos, em comparação à situação sem controle da infestante, independente da dose e do sistema de aplicação. The objective of this research was to evaluate the effects of the utilization of glyphosate and imidazolinones herbicides, in isolated or associated applications, on the effectiveness of red rice (Oryza sativa) control and grain yield of Clearfield-rice. The experiment was conducted under field conditions in 2007/08, in Cachoeirinha, RS, Brazil, using a randomized block design in a two-factorial design 2x6, with four replicates. The factor A was composed by two levels of glyphosate, applied during the subperiod between sowing and crop emergence at the early coleoptile stage of the rice plants; and the factor B consisted of six treatments with imazethapyr+imazapic, applied in association with glyphosate or when the rice crop plants had three expanded leaves. The crop and weed populations, red rice control and grain yield of crop were evaluated. The results show that the glyphosate application at the early coleoptile stage of the crop reduced 75% the red rice population and increased 40% the grain yield, in relation to the situation without weed control. The use of imidazolinones and their association with glyphosate provided effective control of red rice and increased the grain yield, independent of rates and application system.