Considered one of the most devastating plant–parasitic nematodes worldwide,
Bursaphelenchus xylophilus
(commonly known as pinewood nematode, PWN) is the causal agent of the pine wilt disease in the ...Eurasian coniferous forests. This migratory parasitic nematode is carried by an insect vector (
Monochamus
spp.) into the host tree (
Pinus
species), where it can feed on parenchymal cells and reproduce massively, resulting in the tree wilting. In declining trees, PWN populations are strongly dependent on fungal communities colonizing the host (predominantly ophiostomatoid fungi known to cause sapwood blue-staining, the blue-stain fungi), which not only influence their development and life cycle but also the number of individuals carried by the insect vector into a new host. Our main aim is to understand if PWN-associated mycobiota plays a key role in the development of PWD, in interaction with the PWN and the insect vector, and to what extent it can be targeted to disrupt the disease cycle. For this purpose, we characterized the fungal communities of
Pinus pinaster
trees infected and non-infected with PWN in three collection sites in Continental Portugal with different PWD temporal incidences. Our results showed that non-infected
P. pinaster
mycoflora is more diverse (in terms of abundance and fungal richness) than PWN-infected pine trees in the most recent PWD foci, as opposed to the fungal communities of long-term PWD history sites. Then, due to their ecological importance for PWN survival, representatives of the main ophiostomatoid fungi isolated (
Ophiostoma, Leptographium
, and
Graphilbum
) were characterized for their adaptative response to temperature, competition in-between taxa, and as food source for PWN. Under the conditions studied,
Leptographium
isolates showed promising results for PWN control. They could outcompete the other species, especially
O. ips
, and significantly reduce the development of PWN populations when compared to
Botrytis cinerea
(routinely used for PWN lab culturing), suggesting this to be a natural antagonist not only for the other blue-stain species but also for the PWN.
Soil with excess Mn induces toxicity and impairs crop growth. However, with the development in the soil of an intact extraradical mycelia (ERM) from arbuscular mycorrhizal fungi (AMF) symbiotic to ...native Mn-tolerant plants, wheat growth is promoted due to a stronger AMF colonization and subsequent increased protection against Mn toxicity. To determine the biochemical mechanisms of protection induced by this native ERM under Mn toxicity, wheat grown in soil from previously developed
(LOL) or
(ORN), both strongly mycotrophic plants, was compared to wheat grown in soil from previously developed
(SIL), a non-mycotrophic plant. Wheat grown after LOL or ORN had 60% higher dry weight, ca. two-fold lower Mn levels and almost double P contents. Mn in the shoots was preferentially translocated to the apoplast along with Mg and P. The activity of catalase increased; however, guaiacol peroxidase (GPX) and superoxide dismutase (SOD) showed lower activities. Wheat grown after ORN differed from that grown after LOL by displaying slightly higher Mn levels, higher root Mg and Ca levels and higher GPX and Mn-SOD activities. The AMF consortia established from these native plants can promote distinct biochemical mechanisms for protecting wheat against Mn toxicity.
The impacts of a rapidly changing environment together with the growth in global trade activities has promoted new plant pest pandemic events in forest ecosystems. The pinewood nematode (PWN),
, ...causes strong worldwide economic and ecological impacts. Direct control is performed through trunk injection of powerful nematicides, however many of these (hemi)synthetic compounds have raised ecological and human health concerns for affecting non-target species and accumulating in food products. As sustainable alternatives, essential oils (EOs) have shown very promising results. In this work, available literature on the direct activity of EOs against PWN is reviewed, as a contribution to advance the search for safer and greener biopesticides to be used in sustainable PWD pest management strategies. For the first time, important parameters concerning the bioassays performed, the PWNs bioassayed, and the EOs used are summarized and comparatively analyzed. Ultimately, an overview of the chemical composition of the most active EOs allowed to uncover preliminary guidelines for anti-PWN EO efficiency. The analysis of important information on the volatile phytochemicals composing nematicidal EOs provides a solid basis to engineer sustainable biopesticides capable of controlling the PWN under an integrated pest management framework and contributes to improved forest health.
This paper reports the development of carbon paste electrode (CPE) modified with biochar (BC) and copper(II) 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecafluoro-29H,31 phtalocyanine (CuHPc) used ...for the sensitive and selective detection of glyphosate in different matrices. The characterizations of the materials were performed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Fourier-transform infrared spectroscopy (FTIR). The analytical efficiency of the modified electrodes (CuHPc/CPE and BC-CuHPc/CPE) used for glyphosate detection was evaluated by square-wave voltammetry (SWV). The application of BC-CuHPc/CPE resulted in an improvement in the electron transfer process on the electrode surface, and this led to an outstanding increase of 100% in its current signal compared to CuHPc/CPE. Under optimized conditions, the BC-CuHPc/CPE sensor presented a linear concentration range of 0.3–4 µmol L
−1
and a limit of detection of 0.02 µmol L
−1
. Interference analysis was conducted using different compounds that can be found in the environment including 2,4-D, atrazine, diuron, urea, and caffeine; the results obtained showed that the compounds did not exert any interference in the current peak of the glyphosate. The proposed method was applied for the determination of glyphosate in river water and food samples, where recovery rates of nearly 100% were obtained. The results demonstrate the accuracy and reliability of the proposed modified electrode.
Graphic abstract
Climate change is prompting a shift of tropical pests to locations with a previously lower probability of invasion. This is the case for root-knot nematodes, Meloidogyne sp., particularly of the ...tropical group. Among them, M. ethiopica is now considered a threat to European food security. The development of novel sustainable nematicides can be based on in vitro bioassays of highly active phytochemicals, e.g., volatiles from essential oils. However, a steady supply of nematodes is often very difficult and dependent on environmental conditions. In the present study, an in vitro co-culture system of M. ethiopica parasitizing hairy roots of Solanum lycopersicum was established, for the first time, to easily obtain populations of second-stage juveniles (J2). These were then used to screen the nematicidal activity of 10 volatile compounds characteristic of essential oils. Finally, information on the most successful compounds was reviewed to predict their environmental dispersion and ecotoxicological hazards. The M. ethiopica population obtained from the co-culture was morphologically similar to reported populations in natural conditions and could be accurately used in direct-contact bioassays. The aldehydes citral and citronellal induced complete mortality of the tested J2, at 1 mg/mL, while compounds from other chemical groups were not as successful. In comparison to commonly used commercial nematicides, citral and citronellal were less likely to accumulate in the water environmental compartment and have lower reported toxicities compared to aquatic organisms and to mammals. Overall, in vitro co-cultures showed the potential to expedite the screening and discovery of bioactive compounds as a contribution to the development of sustainable biopesticides, as well as to lower the impacts of modern farming on agroecosystems.
El artículo busca resaltar la relevancia de la fase de planificación para lograr los propósitos de las directivas de contratación pública y examinar las regulaciones que abordan de forma expresa la ...fase de planeación, es decir, las normas relativas a avisos de información previa y consultas preliminares de mercado. El análisis también considera algunas pautas sobre los aspectos principales que deben tenerse en cuenta al abordar la fase de planeación. Se argumenta que el enfoque regulatorio europeo para la fase de planeación es insuficiente para mejorar los impactos positivos que una planificación efectiva puede tener en el resultado de la contratación pública.
In acidic soils with manganese (Mn) toxicity, arbuscular mycorrhizal fungi (AMF) can improve plant host growth by enhancing nutrition and protecting against environmental stress. The intact ...extraradical mycelium (ERM) of AMF is able to survive Mediterranean summer conditions and provide an earlier colonization of winter crops. This study evaluated if summer season conditions hindered the beneficial effects of wheat colonization by the intact ERM associated with a native plant, in acidic soil. Wheat was grown in soil with intact or disrupted ERM associated with Ornithopus compressus (ORN), developed for 7 or 24 weeks, to simulate ERM summer survival. The activity of antioxidant enzymes was determined, and the quantitative analysis of Mn and macronutrients was performed by inductively coupled plasma mass spectrometry (ICP-MS), in wheat shoots and respective subcellular fractions. Wheat colonization by intact ERM decreased shoot Mn concentration but increased the proportion of Mn in the apoplast. Overall, antioxidant enzymatic activity decreased but the proportion of Mn-superoxide dismutase activity over the remaining isoforms increased, suggesting its important role in the AMF-mediated mitigation of Mn toxicity. Summer conditions did not substantially reduce the benefits provided by ORN ERM. A no-till strategy allied to the development of native microbiota can contribute to the sustainable optimization of acidic soil use.
Pine wilt disease (PWD) is a complex disease that severely affects the biodiversity and economy of Eurasian coniferous forests. Three factors are described as the main elements of the disease: the ...pinewood nematode (PWN) Bursaphelenchus xylophilus, the insect-vector Monochamus spp., and the host tree, mainly Pinus spp. Nonetheless, other microbial interactors have also been considered. The study of mycoflora in PWD dates back the late seventies. Culturomic studies have revealed diverse fungal communities associated with all PWD key players, composed frequently of saprophytic fungi (i.e., Aspergillus, Fusarium, Trichoderma) but also of necrotrophic pathogens associated with bark beetles, such as ophiostomatoid or blue-stain fungi. In particular, the ophiostomatoid fungi often recovered from wilted pine trees or insect pupal chambers/tunnels, are considered crucial for nematode multiplication and distribution in the host tree. Naturally occurring mycoflora, reported as possible biocontrol agents of the nematode, are also discussed in this review. This review discloses the contrasting effects of fungal communities in PWD and highlights promising fungal species as sources of PWD biocontrol in the framework of sustainable pest management actions.
Acidic soils can promote the bioavailability of Al, Mn, and Fe to toxic levels, reducing crop growth and productivity. Symptoms of metal excess/deficit are dependent on the chemical composition of ...the soil solution and of plant tissues. In the present study, the concentration and subcellular distribution of Al, Mn, Fe, and Si (known to alleviate metal stress) were quantified through inductively coupled plasma mass spectrometry (ICP-MS) in roots and shoots of wheat grown in acidic soils with rising levels of Mn. In control acidic soil, wheat showed high concentrations of Al, Mn, and Fe. After Mn supplementation, bioavailable Al, Fe, and Si levels increased in the soil solution, but plant uptake ratio decreased. Root Mn levels increased, while those of Al, Fe, and Si decreased. Although elements were increasingly translocated to the shoot, root Al and Fe concentrations were 10-fold higher than those in the shoot. At the highest Mn concentration supplied, Al, Fe, and Si proportions increased in the organelles, while Mn proportion increased in the vacuole. High bioavailable Mn levels disrupt metal homeostasis in wheat grown in acidic soils, influencing element subcellular distribution. Symptoms of metal toxicity result from interactions between several elements, and therefore a comprehensive chemical analysis of soil solution and plant tissues contributes to a more accurate understanding of their uptake dynamics and their agronomic implications.
Plant-parasitic nematodes (PPNs) are highly damaging pests responsible for heavy losses in worldwide productivity in a significant number of important plant crops. Common pest management strategies ...rely on the use of synthetic chemical nematicides, which have led to serious concerns regarding their impacts on human health and the environment. Plant natural products, or phytochemicals, can provide a good source of agents for sustainable control of PPNs, due to their intrinsic characteristics such as higher biodegradability, generally low toxicity for mammals, and lower bioaccumulation in the environment. In this work, the nematicidal activity of 39 phytochemicals was determined against the root-lesion nematode (RLN)
using standard direct and indirect contact methodologies. Overall, the RLN was tolerant to the tested phytochemicals at the highest concentration, 2 mg/mL, seldom reaching full mortality. However, high activities were obtained for benzaldehyde, carvacrol, 3-octanol, and thymol, in comparison to other phytochemicals or the synthetic nematicide oxamyl. These phytochemicals were seen to damage nematode internal tissues but not its cuticle shape. Also, the environmental and (eco)toxicological parameters reported for these compounds suggest lower toxicity and higher safety of use than oxamyl. These compounds appear to be good candidates for the development of biopesticides for a more sustainable pest management strategy.
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