Control of the pinewood nematode (PWN), the causal agent of pine wilt disease, can be achieved through the trunk injection of nematicides; however, many pesticides have been linked to environmental ...and human health concerns. Essential oils (EOs) are suitable alternatives due to their biodegradability and low toxicity to mammals. These complex mixtures of plant volatiles often display multiple biological activities and synergistic interactions between their compounds. The present work profiled the toxicity of eight EOs against the PWN in comparison to their 1:1 mixtures, to screen for successful synergistic interactions. Additionally, the main compounds of the most synergistic mixtures were characterized for their predicted environmental fate and toxicity to mammals in comparison to emamectin benzoate, a commercial nematicide used against PWN. The mixtures of
with
and of
with
EOs showed the highest activities, with half-maximal effective concentrations (EC
) of 0.09 and 0.05 µL/mL, respectively. For these, complete PWN mortality was reached after only ca. 15 min or 2 h of direct contact, respectively. Their major compounds had a higher predicted affinity to air and water environmental compartments and are reported to have very low toxicity to mammals, with low acute oral and dermal toxicities. In comparison, emamectin benzoate showed lower nematicidal activity, a higher affinity to the soil and sediments environmental compartments and higher reported oral and dermal toxicity to mammals. Overall, uncovering synergistic activities in combinations of EOs from plants of different families may prove to be a source of biopesticides with optimized toxicity against PWNs.
As a nematotoxics screening biotechnological system, Solanum tuberosum hairy roots (StHR) and S. tuberosum hairy roots with Meloidogyne chitwoodi co-cultures (StHR/CRKN) were evaluated, with and ...without the addition of the essential oils (EOs) of Satureja montana and Ruta graveolens. EOs nematotoxic and phytotoxic effects were followed weekly by evaluating nematode population density in the co-cultures as well as growth and volatile profiles of both in vitro cultures types. Growth, measured by the dissimilation method and by fresh and dry weight determination, was inhibited after EO addition. Nematode population increased in control cultures, while in EO-added cultures numbers were kept stable. In addition to each of the EOs main components, and in vitro cultures constitutive volatiles, new volatiles were detected by gas chromatography and gas chromatography coupled to mass spectrometry in both culture types. StHR with CRKN co-cultures showed to be suitable for preliminary assessment of nematotoxic EOs.
The rice root-knot nematode (RRKN), Meloidogyne graminicola Golden and Birchfield 1965, is a dangerous crop pest that affects rice production on a global scale. The largest rice-producing countries ...struggle with the impacts of RRKN infestation, namely, underdeveloped plants and a reduction in rice grain that can reach up to 70% of crop yield. In addition, the shift to strategies of sustainable pest management is leading to a withdrawal of some of the most effective pesticides, given the dangers they pose to the environment and human health. Volatile metabolites produced by plants can offer safer alternatives. The present study characterized the nematicidal activity of volatile phytochemicals against the RRKN and compared the most active with commercial nematicides concerning their safety to the environment and human health. Rice plants were used to grow large numbers of RRKNs for direct-contact bioassays. Mortality induced by the volatiles was followed for four days on RRKN second-stage juveniles. Of the 18 volatiles tested, carvacrol, eugenol, geraniol, and methyl salicylate showed the highest mortalities (100%) and were compared to traditional nematicides using (eco)toxicological parameters reported on freely available databases. While methyl salicylate had a faster activity, carvacrol had more lasting effects. When compared to synthetic nematicides, these volatile phytochemicals were reported to have higher thresholds of toxicity and beneficial ecotoxicological parameters. Ultimately, finding safer alternatives to traditional pesticides can lower the use of damaging chemicals in farming and leverage the transition to agricultural practices with a lower impact on biodiversity.
Soil acidity can reduce crop growth by increasing bioavailable soil Al, Fe, and/or Mn to toxic levels. The presence of an intact extraradical mycelium (ERM) of arbuscular mycorrhizal fungi (AMF), ...developed by the native Ornithopus compressus in the acidic soil, can increase wheat growth and prevent symptoms of Mn toxicity. To understand the protective effect of the intact ERM of this native plant on wheat element balance and distribution, in the present study, shoot Al, Fe, K, Zn, Na, and Si levels and their subcellular partitioning were determined by inductively coupled plasma mass spectrometry (ICP-MS), for the first time, for this system. In undisturbed soil, where an intact ERM structure is maintained, wheat shoot growth was promoted, probably due to faster root mycorrhizal colonization. The levels of potentially toxic Al and Fe were reduced, the proportions of the macronutrient K and micronutrient Zn were higher in the symplast, and the Na proportion increased in the vacuole, while Si increased in the apoplast. Overall, the undisturbed soil from O. compressus treatment appeared to influence the uptake and distribution of essential and beneficial elements, as a strategy to reduce the negative effect of soil acidity on wheat growth. Understanding the dynamics of element distribution influenced by stress-adapted AMF on wheat growth can provide more sustainable approaches to intensive agriculture.
Display omitted
•Satureja montana and Ruta graveolens essential oils were added to plant/nematode co-cultures.•Essential oils nematotoxicity and phytotoxicity was assessed at 0.5μl/ml culture ...medium.•Pinus pinaster shoots and P. pinaster with Bursaphelenchus xylophilus co-cultures were the test systems.•S. montana essential oil showed phytotoxicity, inducing in vitro shoot chlorosis and drooping.•R. graveolens essential oil induced no detectable morphological changes.
Satureja montana (winter savory) and Ruta graveolens (rue) nematotoxic essential oils (EOs) (0.5μl EO/ml culture medium) were assessed for the first time in Pinus pinaster in vitro shoot cultures (Ppi) and P. pinaster shoots with Bursaphelenchus xylophilus co-cultures (PpiBx). The EOs nematotoxic effect was evaluated on B. xylophilus population density in PpiBx co-cultures and the phytotoxic activity to the host was assessed by evaluating relative water content and volatile profiles both on Ppi cultures and on PpiBx co-cultures. Carvacrol-rich S. montana EO showed phytotoxicity, by inducing shoot chlorosis and drooping, whereas no major morphological changes were detected on R. graveolens EO-added Ppi and PpiBx in vitro cultures. Both EOs maintained the nematotoxicity during all experimental phases. R. graveolens EO proved to be an effective PWN antagonist to be further evaluated for pine wilt disease control, given its less phytotoxicity while maintaining nematoxicity.
Soil acidity is a strong promoter of the bioavailability of Al, Fe, and Mn, whose concentrations can sometimes reach toxic levels for plants. In agricultural soils, the use of arbuscular mycorrhizal ...fungi (AMF) has shown a protective influence on wheat growth under Mn toxicity. The intact extraradical mycelium (ERM) promotes faster AMF colonization, leading to a higher wheat shoot weight, lower Mn uptake, and changes in antioxidant enzyme activity. Its effect on the uptake and distribution of plant nutrients according to the developmental stage of shoot organs has seldomly been analyzed. In the present study, Mn, Mg, Ca, and K were quantified by ICP–MS in leaves and apical meristems of wheat grown in soil with two different ERM consortia, developed from the native plants Lolium rigidum (LOL) and Ornithopus compressus (ORN). The ORN treatment induced the highest wheat shoot weights and the lowest Mn levels. In the leaves, no significant differences were detected for Mg, Ca, or K, but in the apical meristems, the ORN treatment slightly lowered the Ca concentration. The AMF associated with ORN was seen to enhance wheat weight partly by protecting the zones of active growth against high Mn levels in Mn toxic soils. The use of ORN in acidic soils with Mn toxicity provides a sustainable alternative and an efficient complement to current farming practices to lower the negative impacts of farming on the environment.
The biotransformation capacity of Levisticum officinale W.D.J. Koch hairy root cultures was studied by evaluating the effect of the addition of 25 mg/L menthol or geraniol on morphology, growth, and ...volatiles production. L. officinale hairy root cultures were maintained for 7 weeks in SH medium, in darkness at 24 degrees C and 80 r.p.m., and the substrates were added 15 days after inoculation. Growth was evaluated by measuring fresh and dry weight and by using the dissimilation method. Volatiles composition was analyzed by GC and GC-MS. Hairy roots morphology and growth were not influenced by substrate addition. No new volatiles were detected after menthol addition and, as was also the case with the control cultures, volatiles of these hairy roots were dominated by (Z)-falcarinol (1-45%), N-octanal (3-8%), palmitic acid (3-10%), and (Z)-ligustilide (2-9%). The addition of geraniol induced the production of six new volatiles: nerol/citronellol/neral (traces-15%), alpha-terpineol (0.2-3%), linalool (0.1-1.2%), and geranyl acetate (traces-2%). The relative amounts of the substrates and some of their biotransformation products decreased during the course of the experiment. Following the addition of beta-glycosidase to the remaining distillation water, analysis of the extracted volatiles showed that lovage hairy roots were able to convert both substrates and their biotransformation products into glycosidic forms. GC:gas chromatography GC-MS:gas chromatography-mass spectrometry SH:Schenk and Hildebrandt (1972) culture medium.
ABSTRACT Deforestation requests to government decision-makers aim for the legal permission to remove secondary forests for economic reasons. In the State of Rio de Janeiro, Resolução Conama nº ...06/1994 drives the analysis of successional stages of such forests. It does not define which inclusion criterion (diameter at breast height) should be used in forest inventories. We used Floresta da Cicuta as a case study to evaluate the influence of different inclusion criteria on species richness, diversity and structure parameters having Resolução Conama nº 06/1994 as background. Using Hill numbers, we found that the DBH ≥ 2.5 cm highlighted species richness. Species richness is improperly addressed in Resolução Conama nº 06/1994. The use of DBH ≥ 2.5 cm detected 30 individuals of threatened species, while DBH ≥ 10 cm detected only nine. Basal area was the most accurate parameter to identify the successional stage. Mean DBH and mean height misidentified successional stage. We strongly advise environmental authorities to demand the use of DBH ≥ 2.5 cm in forest inventories for deforestation requests. We strongly encourage the review of Resolução Conama nº 06/1994 by environmental authorities in order to reduce the risk of mistaken classification of successional stage of secondary forests.
The Columbia root-knot nematode (CRKN), Meloidogyne chitwoodi, is an EPPO A2 type quarantine pest since 1998. This nematode causes severe damage in economically important crops such as potato and ...tomato, making agricultural products unacceptable for the fresh market and food processing. Commonly used nematicidal synthetic chemicals are often environmentally unsafe. Essential oils (EOs) may constitute safer alternatives against RKN. EOs, isolated from 56 plant samples, were tested against CRKN hatching, in direct contact bioassays. Some of the most successful EOs were fractionated and the hydrocarbon molecules (HM) and oxygen-containing molecules (OCM) fractions tested separately. 24 EOs displayed very strong hatching inhibitions (≥90 %) at 2 µL mL⁻¹ and were further tested at lower concentrations. Dysphania ambrosioides, Filipendula ulmaria, Ruta graveolens, Satureja montana and Thymbra capitata EOs revealed the lowest EC₅₀ values (<0.15 µL mL⁻¹). The main compounds of these EOs, namely 2-undecanone, ascaridol, carvacrol, isoascaridol, methyl salicylate, p-cymene and/or γ-terpinene, were putatively considered responsible for CRKN hatching inhibition. S. montana and T. capitata OCM fractions showed hatching inhibitions higher than HM fractions. The comparison of EO and corresponding fractions EC₅₀ values suggests interactions between OCM and HM fractions against CRKN hatching. These species EOs showed to be potential environmentally friendly CRKN hatching inhibitors; nonetheless, bioactivity should be considered globally, since its HM and OCM fractions may contribute, diversely, to the full anti-hatching activity.
We present a robust, entirely solution-based processing route for the deposition of planar F8BT/TFB poly(9,9-dioctylfluorene- alt -benzothiadiazole)/poly(9,9-dioctylfluorene- alt-N ...-(4-butylphenyl)-diphenylamine) emissive/hole transport bilayers for emission colour tuning in inverted organic–inorganic hybrid light emitting diodes (HyLEDs). Our method allows the facile exploration of TFB thickness for the first time within inverted devices; here we describe the influence of TFB thickness on the device performance. In particular, we demonstrate significant variations in device electroluminescence with highly controlled tunability between green and orange (550 to 610 nm) emission; correlating directly with the thickness of the TFB layer. These changes are in parallel with a 20-fold increase in current efficiency with respect to F8BT-only devices, with our bilayer devices exhibiting luminance values exceeding 11 000 cd m −2 . Additionally, through reflectance and angle-dependent electroluminescence measurements we explore the presence of microcavity effects and their impact on device behaviour. We introduce TFB not only as a charge blocking/transporting layer but also as an optical emission-tuning layer.
PDF
