Field and greenhouse research was conducted in 2009 and 2010 on herbicide applications enabled by the integration of Optimum GAT crop traits providing for resistance to glyphosate and certain ALS-inhibiting herbicides. The herbicide concepts were evaluated for control of several winter and summer annual weed species, as well as the effect of the resulting weed control on grain yield of Optimum GAT soybean. The combination of chlorimuron + rimsulfuron did not provide sufficient efficacy on the winter annual grass species little barley and annual bluegrass. Factors contributing the sub-lethal activity include: 1) a relatively low inherent sensitivity of the species to these herbicides, 2) a significant reduction in herbicide efficacy with increases in weed plant height, and 3) a lack of herbicide enhancement with more aggressive foliar adjuvants. The tank-mixture of glyphosate with chlorimuron + rimsulfuron was frequently necessary to achieve a maximum herbicide activity above 90% on annual bluegrass and little barley. Optimum GAT herbicide treatments including chlorimuron + rimsulfuron + flumioxazin in field experiments provided the greatest control of horseweed and common waterhemp in glyphosate-susceptible and -resistant populations. The addition of chlorimuron + rimsulfuron to glyphosate and 2,4-D improved horseweed control above glyphosate and 2,4-D applied alone even as weed height increased with applications made closer to soybean planting. However, removal of competitive vegetation with herbicide combinations including chlorimuron + rimsulfuron selected for emergence of ALS-resistant common waterhemp. Inclusion of flumioxazin with chlorimuron + rimsulfuron was beneficial for control of common waterhemp when applied 7 days before planting. However, chlorimuron + rimsulfuron + flumioxazin provided only 80% control of common waterhemp in a glyphosate-resistant population which demonstrates opportunity for improvement in herbicide concepts enabled by Optimum GAT. Grain yield of Optimum GAT soybean was greatest for herbicide treatments which provided effective weed management throughout the growing season which were the herbicide treatments applied the closest to soybean planting (7 days before planting). Optimum GAT herbicide concepts for corn include chlorimuron + thifensulfruon + tribenuron, chlorimuron + rimsulfuron, and rimsulfuron + tribenuron + mesotrione. These herbicides provided similar to slightly increased control of annual morningglory (Ipomoea spp.) in comparison to glyphosate alone. The addition of atrazine increased the consistency of control of annual morningglory for any herbicide treatment with additional residual activity at 28 days after treatment. Optimum GAT enabled herbicide concepts can improve control of some problematic weed species, including some glyphosate-resistant weed populations, compared to current herbicide tactics that rely primarily on glyphosate for weed control in commercial glyphosate-resistant soybean and corn. However, the integration of postemergence soybean herbicides beyond the ALS chemistry is necessary to provide a broader spectrum of weed control when considering the challenges of managing both glyphosate- and ALS-resistant weed species that are becoming more frequent in commercial fields.

La toxicité cellulaire potentielle de la sulcotrione 2-(2-chloro-4-(methylsulfonyl)benzoyl)-1,3-cyclohexanedione, un herbicide sélectif tricétonique a été évaluée sur Vicia faba et Allium cepa. La génotoxicité a été étudiée sur une culture hydroponique pour des traitements à différentes concentrations de sulcotrione 10-5, 10-4 et 2.10-4 M pendant 45 h. Nos résultats ont montré que la sulcotrione provoque une augmentation dose-dépendante de la fréquence des micronoyaux dans les cellules méristèmatiques des racines. Elle induit des altérations chromosomiques à la concentration la plus faible (10-5M) mais aussi une baisse de l’indice mitotique, ce qui indique l'effet mutagène puissant de cette molécule. C’est le premier travail montrant une génotoxicité de la sulcotrione. Les signes d’intoxication se manifestent par les perturbations de la croissance foliaire et racinaires accompagnées d’un brunissement des racines traitées de Vicia faba. Sulcotrione, Mikado®, marc de raisin et des mélanges de sulcotrione ou Mikado® et de marc de raisin induisent la mort cellulaire. La présence des herbicides ainsi que celle des cocktails ont entrainé l’installation d’un état de stress oxydant caractérisé par une production accrue d’H2O2. La production de radicaux d’oxygène actif s’accompagne d’une augmentation de la production de MDA et un accroissement de la mort cellulaire. L’ajout de l’extrait de raisin aux herbicides, soit à la sulcotrione ou au Mikado®, modifie l'expression des gènes habituellement associés au stress cellulaire. Les cocktails et les herbicides modifient l’expression des gènes hsp70.1, cat, ubiquitin, APX, CuZnSOD cy et CuZnSOD ch. Des mécanismes de défense, d’induction de gènes associés au stress et de génotoxicité sont discutés. / Potential cell toxicity of sulcotrione 2-(2-Chloro-4-(methylsulfonyl)benzoyl)-1,3 cyclohexanedione), a selective triketonic herbicide was evaluated on Vicia faba and Allium cepa . Genotoxicity was studied in hydroponic culture conditions for treatment at different pesticide concentrations 10-5, 10-4 and 2.10-4 M for 45 h. Our results showed that sulcotrione treatments caused a dose dependent increase of micronucleus frequencies in root meristematic cells. Sulcotrione induced chromosomal alterations at the lowest concentration used (10-5M) when incubated for 42 h. We have shown a decrease in mitotic index, indicating a potent mutagenic effect of this element. This is the first report for the genotoxicity of such a sulcotrione herbicide. It induced a growth inhibition in both leaves and roots and a brownish color in treated roots. Sulcotrione, trade mark Mikado®, grape marc and mixtures of sulcotrione or Mikado® and grape marc induce cell death. The herbicides, cocktails of products with sulcotrione, such as adjuvant in commercial product, induced several changes for antioxidant cell state characterized by an overproduction of H2O2. Production of harmful radicals was accompanied by increased production of MDA and increase of the cell death rate. Addition of grape extracts to herbicides, either sulcotrione or Mikado®, had different effects and results in different expression of genes usually associated to cell stress. Mixture of grape marc and herbicides enhanced transcript accumulation for different effects and results in different expression of some stress-related genes like hsp70.1, cat, ubiquitin, APX, CuZnSOD cy et CuZnSOD ch. Mechanisms which could be associated to gene expression, cell defense and genotoxidity are discussed.

Tomato is a major horticulture crop grown across the globe. Unfortunately, its yield is reduced by 25% because of auxin herbicides and glyphosate drift. In this present study, wild germplasm of tomato was screened for herbicide tolerance. From the greenhouse study nine accessions for glyphosate and 2,4-D, eleven accessions for dicamba, five accessions for quinclorac, eight accessions for aminocyclopyrachlor, and two accessions for picloram and aminopyralid were identified to be tolerant. A few accessions were selected from each herbicide tolerant group for field trials at two locations in Mississippi in 2016 and 2017. Results indicated that TOM18 was most tolerant to dicamba herbicide, while TOM87 and TOM129 to glyphosate and quinclorac herbicide, respectively, on the basis of yield and injury. Molecular experiments were conducted to measure the genetic diversity among diverse germplasm. Genetic diversity analysis showed wild accessions to be highly diverse as compared to cultivated tomato.

Advancements in cold tolerance of seeded bermudagrass and introduction of sulfonylurea herbicides have given turf managers new tools. Seedling bermudagrass response to sulfonylurea herbicides applied before or soon after seeding has not been characterized. Field observations have indicated that variability exists among sulfonylurea herbicides used for perennial ryegrass control. Objectives of the conducted research were to evaluate sulfonylurea herbicides for safety and utility while establishing seeded bermudagrass, and to elucidate variability in perennial ryegrass control with foramsulfuron. Field experiments were conducted in Blacksburg, VA to assess turfgrass and smooth crabgrass response to flazasulfuron, foramsulfuron, metsulfuron, rimsulfuron, sulfosulfuron, and trifloxysulfuron-sodium, applied 1 and 3 weeks after and before seeding. Herbicides applied 3 weeks after seeding (WAS) were generally more injurious than when applied 1 WAS. Foramsulfuron, metsulfuron, and sulfosulfuron are safe to apply 1 and 3 WAS, causing no reduction in turf cover. Herbicides applied before or after seeding injured bermudagrass in the following order from most to least injurious: flazasulfuron = trifloxysulfuron > rimsulfuron > metsulfuron = sulfosulfuron > foramsulfuron. Flazasulfuron and trifloxysulfuron-sodium are not safe to use within 3 weeks of seeding, while foramsulfuron and metsulfuron can be used anytime before or after seeding bermudagrass. Flazasulfuron, foramsulfuron, and trifloxysulfuron-sodium were evaluated for perennial ryegrass control as affected by environment. Among environmental variables collected soil temperature averaged 7 DAT correlated best with perennial ryegrass response of the three tested products. Soil temperatures below 18 C perennial ryegrass reduced control 9 WAT from 78 to 31% for foramsulfuron while flazasulfuron and trifloxysulfuron-sodium efficacy were not significantly affected. Temperature dependence on perennial ryegrass control can be ranked from most to least as follows; foramsulfuron > trifloxysulfuron-sodium > flazasulfuron. Studies were conducted to determine absorption and translocation of 14C flazasulfuron when applied to perennial ryegrass roots or foliage. Roots treated with 14C flazasulfuron absorbed 41% of recovered 14C while 25% of 14C moved from treated roots to foliage. It appears root absorption is an important component of flazasulfuron efficacy since most of the absorbed 14C remained in treated leaves and root absorbed 14C moved rapidly to foliage. / Ph. D.

Silvery threadmoss is a problematic weed of golf putting greens, growing interspersed with turf, decreasing aesthetic quality and playability.  Moss is typically controlled postemergence and currently only one herbicide, carfentrazone, is registered for silvery threadmoss control on greens.  Carfentrazone controls moss up to 75% applied at a three week interval throughout the growing season.  Alternatives providing longer residual or more effective control are desirable.  Studies were conducted to examine the growth of moss gametophytes from spores and bulbils and to evaluate turf protection products for pre and postemergence moss control.  Moss gametophytes develop best from spores at 30"aC and from bulbils at 23"aC.  Products which control moss equivalent to carfentrazone (>70%) both pre and postemergent include sulfentrazone, saflufenacil, flumioxazin, oxadiazon, and oxyfluorfen.  Fosamine and fosetyl-Al alone controlled moss equivalent to carfentrazone post-, but not preemergent.  14C glyphosate absorption and translocation through moss colonies was examined from 12 to 192 hours after treatment (HAT) to understand how herbicides are absorbed by silvery threadmoss.  It appears that 14C reaches equilibrium by 24 HAT in capillary water of the moss colony and inside moss tissues.  Subsequently, 14C is lost to the system presumably through microorganism degradation of 14C glyphosate in capillary water.  The final objective of this work was to identify and evaluate two fungal organisms observed to cause disease of silvery threadmoss on putting greens in efforts to develop a biological control.  The organisms were identified by morphology and ITS sequence as Alternaria sp. and Sclerotium rolfsii.  Alternaria sp. causes a leaf disease of silvery threadmoss and Sclerotium rolfsii causes Southern blight of silvery threadmoss.  Host specificity testing demonstrated moderate pathogenicity of S. rolfsii to annual bluegrass but not to "¥Penn A4"" creeping bentgrass.  Both organisms have potential to be effective biological controls for silvery threadmoss; however, host specificity indicates Alternaria sp. may be a better choice.  Data from these experiments suggest herbicides in two chemical classes control mosses both pre and postemergence, and sulfentrazone, fosetyl-Al, and Alternaria sp. may be new alternatives to carfentrazone for use on golf putting greens. / Ph. D.

Safeners protect crops by enhancing their ability to metabolize various compounds, including herbicides. They primarily work by increasing the crop's tolerance to herbicide damage, activating herbicide-metabolizing proteins, and aiding in their detoxification. This study aimed to investigate the chemical effects of safeners in tomato cultivation and focus on injury reduction and tissue protection. The experiment followed a randomized factorial design (5x4) with four replications repeated twice. We evaluated the effects of herbicides (dicamba, 2,4-D, metribuzin, and sulfentrazone at 1/100) and safeners (benoxacor, fenclorim, melatonin, 2,4,6-T, and an untreated control). Safeners were applied to the seeds before sowing, and herbicides were used as a foliar spray 25 days after sowing (DAS). Visual injury was evaluated 7, 14, and 21 days after application (DAA). Biomass measurements were taken 21 DAA. Results showed that preconditioning tomato seeds with 2,4,6-T, melatonin, and fenclorim 7 DAA significantly decreased injury by 25, 25, and 23%, respectively. Moreover, applying melatonin, benoxacor, and 2,4,6-T 21 DAA led to significantly greater dry biomass, which increased by 1.5, 1.42, and 1.44 times, respectively, compared to the control. This research provides valuable insights into the chemical effects of benoxacor, fenclorim, 2,4,6-T, and melatonin safeners in tomato cultivation. The findings demonstrate the potential for preconditional tomato plants with 2,4,6-T, melatonin, and fenclorim to reduce injury while applying melatonin, benoxacor, and 2,4,6-T can increase dry biomass. Understanding plant defense mechanisms and the protective effects of safeners against herbicide damage contributes to developing effective weed management strategies.

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No description available.

No description available.

Glutathione transferases, also known as Glutathione S-transferases (GSTs), are a diverse group of enzymes that catalyse the conjugation of the tri-peptide glutathione to a wide range of electrophilic substrates. Their biological function in endogenous metabolism in plants is not well characterised, although their role in herbicide metabolism and herbicide selectivity is well documented. Many herbicides used in soybean. Glycine max (L.) Merr., are selective against weeds due to their rapid detoxification in the crop through conjugation with homoglutathione (γ-glu-cys-β-ala), the predominant free thiol in many legumes. However, an in depth characterisation of the GSTs which can potentially catalyse these reactions in soybean has never been performed. This work describes the biochemical and molecular characterisation of GSTs in soybean with emphasis on the identification of specific isoenzymes involved in herbicide metabolism. GST activity toward the chloroacetanilide herbicides acetochlor and metolachlor, the diphenyl ethers acifluorfen and fomesafen and the sulphonyl urea chlorimuron-ethyl were all detected in crude protein extracts from five-day-old suspension cultured soybean cells. GST activity was also determined in five-day-old soybean seedlings, though this activity was significantly lower than that observed with the cell suspension cultures. Treatment of soybean plants with herbicides and herbicide safeners resulted in increased GST activity toward the model substrate l-chloro-2,4-dinitrobenzene (CDNB), but no change in activity toward herbicide substrates. In both plant and cell cultures GST-catalysed conjugation of the diphenyl ethers acifluorfen and fomesafen was over five-fold greater in the presence of homoglutathione as compared with glutathione. The preferential detoxification of these herbicides in the presence of homoglutathione appeared to be an important determinant of their rapid detoxification in soybean and an important factor in herbicide selectivity. GSTs were purified from five-day-old soybean cell cultures using S-hexylglutathione affinity chromatography and anion-exchange chromatography. A combination of reversed-phase HPLC, SDS-PAGE and MALDI-TOF mass spectrometry of the purified fractions indicated the presence of nine putative GST subunits, each with a molecular mass between 25 and 29 kDa. Soybean GST cDNA clones were obtained using a combination of RT-PCR, utilising degenerate oligonucleotides designed to conserved regions within plant GSTs, and screening of cDNA libraries prepared from soybean plants and cell cultures. This process failed to identify any theta-type GSTs, the class associated with herbicide detoxification in maize. In contrast, seven distinct tau-type GSTs were isolated together with a number of clones showing minor variations in individual sequences. Expression of these cDNAs in Escherichia coli showed the purified recombinant GSTs were active toward a diverse range of substrates, and possessed additional glutathione peroxidase activity. GST activities for each recombinant enzyme varied with substrate and thiol type, with a marked preference for homoglutathione with selected substrates. From the work reported in this study it would appear that the tau-type GSTs of soybean are at least as complex as those previously reported in cereals and have an important role in determining herbicide metabolism and selectivity in this major crop.