Characterization of the Phytochemical Composition and Bioactivities of Anacyclus maroccanus Ball. and Anacyclus radiatus Loisel Aerial Parts: Preliminary Evidence for the Possible Development of Moroccan Plants.

In the present study, the phytochemical composition and bioactivities of A. maroccanus (AM) and A. radiatus (AR), two ecotypes collected in the Demnate road and Essaouira regions, respectively, were studied to highlight a pharmacological interest and to enable possible pharmaceutical development. To this end, methanolic and ethyl acetate extracts were prepared for each ecotype by fractionation; next, their phytochemical composition was evaluated by spectrophotometric and chromatographic analysis. Moreover, in line with the available evidence for Anacyclus spp. and their traditional use, a screening of bioactivities, including antioxidant, hypoglycemic, antiglycative, chelating, and antibacterial activities, was performed. The extracts were characterized by high amounts of polyphenols, tannins, and flavonoids, especially in the methanolic extracts; these samples were also enriched in carotenoids despite a lower chlorophyll content. Chlorogenic acid and rutin were the major identified compounds. The extracts also showed interesting hypoglycemic, antiglycative, and antibacterial properties, although with differences in efficacy and potency. Present results provide more scientific basis to the ethnopharmacological uses of Anacyclus spp. and suggest a further interest in AM and AR ecotypes as natural sources of bioactive compounds and/or phytocomplexes for possible pharmaceutical and nutraceutical developments.

Bioefficacy of Epaltes divaricata (L.) n-Hexane Extracts and Their Major Metabolites against the Lepidopteran Pests Spodoptera litura (fab.) and Dengue Mosquito Aedes aegypti (Linn.).

The present research investigated the chemical characterization and insecticidal activity of n-Hexane extracts of Epaltes divaricata (NH-EDx) along with their chief derivatives n-Hexadecanoic acid (n-HDa) and n-Octadecanoic acid (n-ODa) against the dengue vector Aedes aegypti and lepidopteran pest Spodoptera litura. Chemical screening of NH-EDx through GC-MS analysis delivered nine major derivatives, and the maximum peak area percentage was observed in n-Hexadecanoic acid (14.63%) followed by n-Octadecadienoic acid (6.73%). The larvicidal activity of NH-EDx (1000 ppm), n-HDa (5 ppm), and n-ODa (5 ppm) against the A. aegypti and S. litura larvae showed significant mortality rate in a dose-dependent way across all the instars. The larvicidal activity was profound in the A. aegypti as compared to the S. litura across all the larval instars. The sublethal dosages of NH-EDx (500 ppm), n-HDa (2.5 ppm), and n-ODa (2.5 ppm) also showed alterations in the larval/pupal durations and adult longevity in both the insect pests. The enzyme activity revealed that the α- and ß-carboxylesterase levels were decreased significantly in both the insect pests, whereas the levels of GST and CYP450 uplifted in a dose-dependent manner of NH-EDx, n-HDa, and n-ODa. Correspondingly, midgut tissues such as the epithelial layer (EL), gut lumen (GL), peritrophic matrix (Pm), and brush border membrane (BBM) were significantly altered in their morphology across both A. aegypti and S. litura against the NH-EDx and their bioactive metabolites. NH-EDx and their bioactive metabolites n-HDa and n-ODa showed significant larvicidal, growth retardant, enzyme inhibition, and midgut toxicity effects against two crucial agriculturally and medically challenging insect pest of ecological importance.

Pre-harvest spray of GABA and spermine delays postharvest senescence and alleviates chilling injury of gerbera cut flowers during cold storage.

Short vase life, capitulum wilting, neck bending, and postharvest chilling injury (CI) are major disorders have negative impact on quality and marketing of gerbera cut flowers. Low storage temperatures prolonging the vase life, but on the other hand leads serious CI which decreases the quality and consumer preferences. Spermine (SPER) and γ-aminobutyric acid (GABA) were identified as anti-aging factors delay the senescence and elevate the chilling tolerance in many species. Greenhouse-grown gerbera cv. 'Stanza' sprayed with 2 mM SPER and 1 mM GABA twice (2 T) or thrice (3 T). Cut flowers were stored at 1.5 °C and 8 °C postharvest to study the effects of GABA and SPER on senescence and CI. Vase life, CI and quality of cut flowers were improved by GABA and SPER treatments. No CI was observed in GABA-treated flowers at 1.5 °C; while, flowers sprayed with water showed severe CI. GABA treatments efficiently prolonged the vase life for 6-7 days more than the control (15 days). GABA and SPER increased the fresh weight, solution uptake, protein and proline contents, catalase, peroxidase, and superoxide dismutase activities, while decreased the electrolyte leakage, H2O2, and malondialdehyde contents, polyphenol oxidase, lipoxygenase, and phospholipase D activities. GABA and SPER significantly prolonged the vase life and prevented degradation of proteins and chilling damage and increased capacity of detoxifying and scavenging of H2O2 and reactive oxygen species (ROS), led to alleviate the negative consequences of the senescence and CI.

Characterization of clopyralid resistance in lawn burweed (Soliva sessilis).

Soliva sessilis is a troublesome annual weed species in New Zealand turfgrass. This weed has been controlled selectively in New Zealand turfgrass for many years using pyridine herbicides such as clopyralid. However, in some golf courses, the continuous application of pyridine herbicides has resulted in the selection of S. sessilis populations that are resistant to these herbicides. This study focuses on a clopyralid-resistant population of S. sessilis collected from a golf course with a long history of clopyralid applications. The resistant phenotype of S. sessilis was highly resistant to clopyralid (over 225-fold). It was also cross-resistant to dicamba, MCPA and picloram but not mecoprop. The level of resistance to dicamba was high (7-14-fold) but much lower (2-3-fold) for both MCPA and picloram. The phenotype was morphologically distinct from its susceptible counterpart. Individuals of the clopyralid-resistant phenotype had fewer lobes on their leaves and were slightly larger compared to the susceptible phenotype. Resistant individuals also had a larger leaf area and greater root dry weight than the susceptible plants. An evaluation of internal transcribed spacer (ITS) regions confirmed that clopyralid-resistant phenotypes are conspecific with S. sessilis. In summary, the cross-resistance to several auxinic herbicides in this S. sessilis phenotype greatly reduces chemical options for controlling it; thus, other integrated management practices may be needed such as using turfgrass competition to reduce weed germination. However, the morphological differences between resistant and susceptible plants make it easy to see, which will help with its management.

Compact shoot architecture of Osteospermum fruticosum transformed with Rhizobium rhizogenes.

KEY MESSAGE: Improved compact shoot architecture of Osteospermum fruticosum Ri lines obtained through Rhizobium rhizogenes transformation reduces the need for chemical growth retardants. Compactness is for many ornamental crops an important commercial trait that is usually obtained through the application of growth retardants. Here, we have adopted a genetic strategy to introduce compactness in the perennial shrub Cape daisy (Osteospermum fruticosum Norl.). To this end, O. fruticosum was transformed using six different wild type Rhizobium rhizogenes strains. The most effective R. rhizogenes strains Arqua1 and ATCC15834 were used to create hairy root cultures from six Cape daisy genotypes. These root cultures were regenerated to produce transgenic Ri lines, which were analyzed for compactness. Ri lines displayed the characteristic Ri phenotype, i.e., reduced plant height, increased branching, shortened internodes, shortened peduncles, and smaller flowers. Evaluation of the Ri lines under commercial production conditions showed that similar compactness was obtained as the original Cape daisy genotypes treated with growth retardant. The results suggest that the use of chemical growth retardants may be omitted or reduced in commercial production systems of Cape daisy through implementation of Ri lines in future breeding programs.

Application of methyl jasmonate and salicylic acid lead to contrasting effects on the plant's metabolome and herbivory.

Phytohormone applications are used to mimic herbivory and can induce plant defences. This study investigated (i) metabolomic changes in leaf tissues of Jacobaea vulgaris and J. aquatica after methyl jasmonate (MeJA) and salicylic acid (SA) applications and (ii) the effects on a leaf-chewing, a leaf-mining and a piercing-sucking herbivore. MeJA treated leaves showed clearly different metabolomic profiles than control leaves, while the differences in metabolomic profiles between SA treated leaves and control leaves were less clear. More NMR peaks increased than decreased after MeJA treatment while this pattern was reversed after SA treatment. The leaf-chewing (Mamestra brassicae) and the leaf-mining herbivores (Liriomyza trifolii) fed less on MeJA-treated leaves compared to control and SA-treated leaves while they fed equally on the latter two. In J. aquatica but not in J. vulgaris, SA treatment reduced feeding damage by the piercing-sucking herbivore (Frankliniella occidentalis). Based on the herbivory and metabolomic data after phytohormone application, we made speculations as follows: For all three herbivore species, plants with high levels of threonine and citric acid showed less herbivory while plants with high levels of glucose showed more herbivory. Herbivory by thrips was lower on plants with high levels of alanine while it was higher on plants with high levels of 3,5-dicaffeoylquinic acid. The plant compounds that related to feeding of piercing-sucking herbivore were further verified with previous independent experiments.

Effect of antimony in soils of an Sb mine on the photosynthetic pigments and antioxidant system of Dittrichia viscosa leaves.

Antimony is a toxic element whose concentration in soil and water has been rising due to anthropogenic activities. This study focuses on its accumulation in leaves of Dittrichia viscosa growing in soils of an abandoned Sb mine, and the effect on oxidant/antioxidant systems and photosynthetic efficiency. The results showed leaves to have a high Sb accumulation capacity. The amount of total chlorophyll decreased depending on Sb concentration and of carotenoids increased slightly, with a consequent increase in carotenoid/chlorophyll ratio. Photosynthetic efficiency was unaffected. The amount of O 2 .- rose, although there was no increase in cell membrane damage, with lipid peroxidation levels being similar to normal. This response may be due to considerable increases that were observed in total phenolics, PPO activity, and enzymatic antioxidant system. SOD, POX, and DHAR activities increased in response to increased Sb amounts in leaves. The ascorbate/glutathione cycle was also affected, with strong increases observed in all of its components, and consequent increases in total contents of the ascorbate and glutathione pools. However, the ratio between reduced and oxidized forms declined, reflecting an imbalance between the two, especially that between GSH and GSSG. Efficient detoxification of Sb may take place either through increases in phenolics, carotenoids, and components of the glutathione-ascorbate cycle or through the enzymatic antioxidant system. Since Dittrichia viscosa accumulates large amounts of Sb without suffering oxidative damage, it could be used for phytoremediation.

Natural products for the management of hyperuricaemia and gout: a review.

Hyperuricaemia is characterised by a high level of urate in the blood. The crystallisation of urate is considered a critical risk factor for the development of gout. Allopurinol and febuxostat have been commonly used medications to decrease the circulating urate levels. However, the use of these drugs is associated with undesired side effects. Therefore, the development of a new active, safety anti-hyperuricaemic and anti-inflammatory drug could be useful in gout therapy and is highly justified. Natural products have become a source of new pharmaceuticals due to their strong efficacy with less side effects, which relies on the comprising of complex bioactive compounds. There are a growing number of studies purporting decreasing serum urate with traditional medicines. This article was aimed to review these studies and identify which extracts promote urate reduction, along with their different mechanisms.

Shoot organogenesis and somatic embryogenesis from leaf and root explants of Scaevola sericea.

An efficient regeneration system via shoot organogenesis and somatic embryogenesis from in vitro leaf and root explants was established for Scaevola sericea for the first time. The highest axillary shoot proliferation coefficient (4.8) was obtained on Murashige and Skoog (MS) medium supplemented with 1.0 mg/L 6-benzyladenine (BA) and 0.1 mg/L α-naphthaleneacetic acid (NAA) every 45 days. Young in vitro leaves and roots, which were used as explants, were cultured onto medium supplemented with different plant growth regulators. Our results showed that only cytokinins BA and thidiazuron (TDZ), could induce adventitious shoots and somatic embryos from leaf and root explants. The optimal medium to achieve this was MS medium supplemented with 2.5 mg/L BA and which induced most adventitious shoots (2.7) and somatic embryos (17.3) from leaf explants within 30 days. From root explants, 1.1 adventitious shoots and 7.6 somatic embryos could be induced on MS medium supplemented with 2.5 mg/L TDZ. Histological observation showed that both somatic embryos and adventitious shoots were originated from homogeneous parenchyma and the development of somatic embryos was visible. Maximum rooting percentage (99.0%) was achieved on half-strength MS medium supplemented with 2.5 mg/L NAA. Well-rooted plantlets, which were transplanted into a substrate of pure river sand, displayed a high survival percentage of 91.7% after transplanting for 45 days while the best substrate for plantlet growth was river sand: coral sand (1:1).

Tolerance of Facultative Metallophyte Carlina acaulis to Cadmium Relies on Chelating and Antioxidative Metabolites.

The impact of long-term chronic cadmium stress (ChS, 0.1 µM Cd, 85 days) or short-term acute cadmium stress (AS, 10 µM Cd, 4 days) on Carlina acaulis (Asteraceae) metabolites was compared to identify specific traits. The content of Cd was higher under AS in all organs in comparison with ChS (130 vs. 16 µg·g-1 DW, 7.9 vs. 3.2 µg·g-1 DW, and 11.5 vs. 2.4 µg·g-1 DW in roots, leaves, and trichomes, respectively) while shoot bioaccumulation factor under ChS (ca. 280) indicates efficient Cd accumulation. High content of Cd in the trichomes from the AS treatment may be an anatomical adaptation mechanism. ChS evoked an increase in root biomass (hormesis), while the impact on shoot biomass was not significant in any treatment. The amounts of ascorbic acid and sum of phytochelatins were higher in the shoots but organic (malic and citric) acids dominated in the roots of plants from the ChS treatment. Chlorogenic acid, but not ursolic and oleanolic acids, was elevated by ChS. These data indicate that both chelation and enhancement of antioxidative power contribute to protection of plants exposed to long-term (chronic) Cd presence with subsequent hormetic effect.

The presence of zinc reduced cadmium uptake and translocation in Cosmos bipinnatus seedlings under cadmium/zinc combined stress.

Cadmium (Cd) and zinc (Zn) coexist in the environment but interact differently in plants. Cosmos bipinnatus has been potentially considered as a Cd-accumulator. Thus, this study investigated the detoxification mechanism in C. bipinnatus seedlings under Cd, Zn and Cd + Zn stresses. In the present study, the presence of Zn inhibited Cd uptake and translocation, whereas Cd merely hindered Zn uptake. The concentration of Cd in soluble fraction significantly decreased and Cd was bounded to the cell wall in root under Cd + Zn stress. Meanwhile, Zn and Cd mutually decreased their concentrations in the ethanol extractable form (FE) and water extractable form (FW) in roots and shoots. Furthermore, Cd + Zn stress enhanced the activities of superoxide dismutase (SOD, EC 1.15.1.1), peroxidase (POD, EC 1.11.1.7) and catalase (CAT, EC 1.11.1.6) compared to Cd stress alone. These results suggested that Zn effectively decreased Cd uptake and translocation, changed their subcellular distributions, regulated their chemical forms composition and increased antioxidative enzyme activities, thereby enhancing the tolerance to Cd in C. bipinnatus. This study physiologically revealed the interactive effect of Cd and Zn on the detoxification mechanism of Cd in C. bipinnatus and provided new information on phytoremediation of the heavy metal contaminated soils.

Cellular alteration and differential protein profile explain effects of GA3 and ABA and their inhibitor on Trichocline catharinensis (Asteraceae) seed germination.

Seed physiology of wild species has not been studied as deeply as that of domesticated crop species. Trichocline catharinensis (Asteraceae) is an endemic wildflower species from the high-altitude fields of southern Brazil. This species is of interest as a source of genes to improve cultivated Asteraceae because of its ornamental features, disease resistance and ability to tolerate drought and poor soil conditions. We studied the effects of abscisic acid (ABA) and gibberellic acid (GA3 ) and their inhibitors, fluridone (FLU) and paclobutrazol (PAC), on seed germination. We individually assessed ultrastructural changes and differential protein accumulation. The principal component analysis explained 69.66% of differential accumulation for 32 proteins at phase II of seed germination in response to hormone and inhibitor treatment. GA3 -imbibed seed germination (98.75%) resulted in increased protein accumulation to meet energy demand, redox regulation, and reserve metabolism activation. FLU-imbibed seeds showed a higher germination speed index as a consequence of metabolism activation. ABA-imbibed seeds (58.75%) showed osmotolerance and flattened cells in the hypocotyl-radicular axis, suggesting that ABA inhibits cell expansion. PAC-imbibed seeds remained at phase II for 300 h, and germination was suppressed (7.5%) because of the increased signaling proteins and halted reserve mobilization. Therefore, our findings provide insight into the behavior of Asteraceae non-dormant seed germination, which broadens our knowledge of seed germination in a wild and endemic plant species from a threatened ecosystem.

Multiple Resistance to Synthetic Auxin Herbicides and Glyphosate in Parthenium hysterophorus Occurring in Citrus Orchards.

Dominican farmers have started to apply synthetic auxin herbicides (SAHs) as the main alternative to mitigate the impacts of the occurrence of glyphosate-resistant (GR) Parthenium hysterophorus populations in citrus orchards. A GR P. hysterophorus population survived field labeled rates of glyphosate, 2,4-dichlorophenoxyacetic acid (2,4-D), dicamba, and picloram, which showed poor control (<50%). In in vivo assays, resistance levels were high for glyphosate and moderate for picloram, dicamba, and 2,4-D. Sequencing the 5-enolpyruvylshikimate-3-phosphate synthase gene revealed the double Thr-102-Ile and Pro-106-Ser amino acid substitution, conferring resistance to glyphosate. Additionally, reduced absorption and impaired translocation contributed to this resistance. Regarding SAH, impaired 2,4-D transport and enhanced metabolism were confirmed in resistant plants. The application of malathion improved the efficacy of SAHs (control >50%), showing that metabolism of these herbicides was mediated by cytochrome P450 enzymes. This study reports, for the first time, multiple resistance to SAHs and glyphosate in P. hysterophorus.

Self-rooted grafting influences the growth and cadmium accumulation characteristics in the post generation of Cosmos sulphureus.

To determine whether self-rooted grafting increases the cadmium (Cd) accumulation in post generations of hyperaccumulator or accumulator plants, a pot experiment was conducted to study the effects of self-rooted grafting on growth and Cd accumulation in the post generation of the accumulator plant Cosmos sulphureus. Four treatments were applied in the experiment with soil Cd concentration of 5 mg kg-1: ungrafted (UG), self-rooted grafting of the same C. sulphureus seedling (SG), self-rooted grafting of two C. sulphureus seedlings at the same growth stage (TG), and self-rooted grafting of two C. sulphureus seedlings at different developmental stages (DG). Compared with those of UG plants, the SG, TG, and DG treatments increased the root, stem, leaf, and shoot biomasses of plants in the post-grafting generation, consistent with the rank order DG > TG > SG > UG. The SG, TG, and DG treatments decreased the Cd contents in different organs of the post-grafting generation compared with those of UG plants. Only DG increased Cd extraction by the shoots in the post-grafting generation, which was increased by 6.28% compared with that of the UG treatment. In addition, SG, TG, and DG increased the photosynthetic pigment contents and enhanced antioxidant enzyme activities in the post-grafting generation compared with those of the UG treatment. Thus, self-rooted grafting promoted growth of C. sulphureus plants in the post generation. The DG treatment increased Cd extraction by C. sulphureus plants in the post-grafting generation, which may be exploited for phytoremediation of urban Cd-contaminated soil.

Effect of elevated carbon dioxide concentration on growth, productivity and glyphosate response of parthenium weed (Parthenium hysterophorus L.).

BACKGROUND: The rise in atmospheric CO2 has huge impacts on the biology and management of invasive weed species such as Parthenium hysterophorus. This study evaluated the effect of ambient (400 ppm) and elevated (700 ppm) CO2 concentrations on P. hysterophorus growth, reproductive output and response to glyphosate applied at several doses including the recommended dose (800 g a.e. ha-1 ). RESULTS: The plants in control treatment (no herbicide) grew taller (41%), produced a larger number of leaves (13%) and flowers (39%), and higher dry biomass (34%) at elevated CO2 as compared to the ambient CO2 . Glyphosate caused significant reduction in chlorophyll content of P. hysterophorus plants grown at both CO2 concentrations in a dose-dependent manner. The percentage herbicide injury was relatively less at elevated CO2 as compared to the ambient CO2 at 7 and 14 days after glyphosate application but it was almost similar at 21 days after application. This shows that elevated CO2 might have slowed the translocation of glyphosate initially, but most plants were killed eventually close to 21 days after application. The survival rate was higher under elevated as compared to the ambient CO2 at recommended and lower doses of glyphosate. There was a negligible difference between the two CO2 concentrations for the plant dry biomass reduction over the control treatment. CONCLUSIONS: P. hysterophorus growth and reproductive potential (indicated by number of flowers) improved significantly by CO2 enrichment but there was little effect on the overall efficacy of glyphosate applied to control this species. © 2019 Society of Chemical Industry.

Tolerance strategies of two Mediterranean native xerophytes under fluoride pollution in Tunisia.

A field study was conducted along a fluorine gradient of soil pollution in Tunisia from Gabes, the most polluted site, to Smara, the reference site. Variations of fluoride (F) concentrations in soils were detected over 1 year in Gabes, Skhira, and Smara. F concentrations in the aerial part of two native plant species, i.e., Erodium glaucophyllum and Rhanterium suaveolens, were above the usual background concentrations. Bioaccumulation factors ranged from 0.08 to 1.3. With F concentrations in aerial parts up to 355 mg kg-1, both species may be described as F accumulators. Both species showed an earlier vegetative growth in Gabes than in Smara. However, some difference between their strategies could be observed, i.e., E. glaucophyllum shortening the period of its vegetative growth with an escape strategy and R. suaveolens decreasing its ratio of alive/dead parts potentially lowering the F toxicity by storage in dead cells. However, at a tissue level, mechanisms of tolerance were similar. Leaf section micrographs of both species showed a higher calcium accumulation in leaf midveins at Gabes than at Smara, confirming the role of calcium in plant F tolerance strategies.

Turn bane into a boon: Application of invasive plant species to remedy soil cadmium contamination.

Cadmium (Cd) is one of the mostly hazardous soil pollutants and has threatened human health by accumulating in grains of crops. Phytoremediation is a promising technique to remedy soil Cd contamination, but reported Cd hyperaccumulators remain limited. In this study, we explored potential applicability of three invasive plant species (Chromolaena odorata, Bidens pilosa and Praxelis clematidea) to remove soil Cd using greenhouse experiment. Results showed that the three species grew well with Cd treatments compared to the controlled individuals, suggesting that the species had high Cd tolerance by physiological adjustments such as up-regulating the antioxidant enzyme activities. The only exception was that the height of P. clematidea in the 60 mg kg-1 Cd treatment was less than that in the control. Within the tested Cd concentration range, the C. odorata exhibited high bioaccumulation characteristics that meet the recommended standards to identify as a hyperaccumulator (shoot Cd concentration > 100 mg kg-1 with bioconcentration and transfer factors > 1). The other two species had also the shoot bioconcentration factor and transfer factor greater than one, while the shoot Cd concentration was relatively lower. Our results highlight a potential applicability of the invasive species used in this study for remediation of the soil Cd contamination, which turns bane into a boon.

In situ phytoremediation of dyes from textile wastewater using garden ornamental plants, effect on soil quality and plant growth.

In situ phytoremediation of dyes from textile wastewater was carried out in a high rate transpiration system ridges (91.4 m × 1.0 m) cultivated independently with Tagetes patula, Aster amellus, Portulaca grandiflora and Gaillardia grandiflora which reduced American Dye Manufacturers Institute color value by 59, 50, 46 and 73%, respectively within 30 d compared to dye accumulated in unplanted ridges. Significant increase in microbial count and electric conductivity of soil was observed during phytoremediation. Reduction in the contents of macro (N, P, K and C), micro (B, Cu, Fe and Mn) elements and heavy metals (Cd, As, Pb and Cr) was observed in the soil from planted ridges due to phyto-treatment. Root tissues of these plants showed significant increase in the specific activities of oxido-reductive enzymes such as lignin peroxidase, laccase, veratryl alcohol oxidase, tyrosinase and azo reductase during decolorization of textile dyes from soil. Anatomical studies of plants roots revealed the occurrence of textile dyes in tissues and subsequent degradation. A minor decrease in plant growth was also observed. Overall surveillance suggests that the use of garden ornamental plants on the ridges of constructed wetland for the treatment of dyes from wastewater along with the consortia of soil microbial flora is a wise and aesthetically pleasant strategy.

Ammonium 2,2'-thiodiacetates - Selective and environmentally safe herbicides.

2,2'-Thiodiacetic acid derivatives have a wide application potential, mainly in coordination chemistry. This research indicates that quaternary ammonium 2,2'-thiodiacetate salts may also be potent herbicidal agents used in agriculture. To provide a rationale for this statement, the toxic effect by a alkyl and aryl quaternary ammonium salts (QASs) on plant growth was investigated. The phytotoxicity of these compounds was tested against cultivated monocotyledonous (spring barley) and dicotyledonous (common radish) plants, whereas herbicidal activity was investigated in relation to popular weeds species (white goosefoot, sorrel and gallant-soldier). The results showed that aliphatic QASs possessed a low phytotoxicity to food crops and that some of them (in particular triethylammonium salt) had potent and selective herbicidal properties against common weeds, such as sorrel and gallant-soldier. However, the investigated compounds appeared to be ineffective herbicides against white goosefoot.

Glyphosate Resistance in Tridax procumbens via a Novel EPSPS Thr-102-Ser Substitution.

This study confirmed the first case of glyphosate resistance in Tridax procumbens and investigated the glyphosate-resistance mechanisms. Sequencing and cloning of the full 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) coding sequences revealed a point mutation (ACC to TCC) at amino acid position 102, resulting in a novel Thr-102-Ser substitution. Other possible resistance mechanisms (i.e., target-site EPSPS-gene overexpression, nontarget-site differential glyphosate uptake and translocation) were also examined and were unlikely to be involved in resistance in this population. Structural modeling of the wild-type and mutant EPSPS in complex with glyphosate and phosphoenolpyruvate (PEP) revealed that the Thr-102-Ser substitution weakly decreased EPSPS affinity to glyphosate, but sharply increased EPSPS affinity to the natural substrate, PEP. Therefore, this novel mutation is very likely responsible for the observed glyphosate resistance in this tetraploid weed species via dual mechanisms of reducing glyphosate binding and favoring PEP binding to EPSPS.