Nematode Mortality Research Articles

Bio Efficacy of Different Fungal Bio-agents on Juvenile Mortality of Root Knot Nematode, Meloidogyne incognita under Laboratory Condition

An investigation was carried out in vitro to evaluate the antagonistic effect of fungal bio-control agents i.e., Trichoderma harzianum, T. viride, Purpureocillium lilacinum, Metarhizium anisopliae and Beauveria bassiana on second stage juvenile (J2) mortality of root-knot nematode (RKN) at 106 and 107 dilutions on juvenile mortality of M. incognita after 24, 48, 72, 96 and 120 hrs exposure period as compared to untreated check. Among different dilutions, T. viride at 106 dilutions (86.00 per cent) gave maximum per cent juvenile mortality followed by T. harzianum at 106 dilutions (82.00 per cent), P. lilacinum at 106 dilutions (76.00 per cent) and T. viride at 107 dilutions (72.00 per cent) after 120 hrs. M. anisopliae at 107 dilutions (38.00 per cent) was found least effective at different period of exposure.Further studies need to be conducted in pot and field conditions to evaluate the efficacy of these bio-agents against root knot nematode, M. incognita.

In vitro nematicidal efficacy of brassica-derived isothiocyanates against the root lesion nematode, Pratylenchus penetrans

Summary Brassica plants naturally produce glucosinolates as secondary metabolites hydrolysed to biocidal isothiocyanates (ITCs). As such, they have the potential for nematode management through a strategy known as biofumigation. Pratylenchus penetrans causes significant yield losses in many important crops. Understanding the relative impact of different ITCs on the motility and mortality of this nematode species could provide some insights into the selection of relevant brassica biofumigants. The effects of 3.125, 6.25, 12.5, 25, and 50 μg ml−1 of pure Allyl, 2-Phenylethyl and Benzyl ITCs on the motility and mortality of P. penetrans were evaluated in laboratory in vitro assays. Motility was assessed after incubating the nematodes in ITCs for 24, 48 and 72 h with distilled water as a negative control. Motile and non-motile nematodes were counted. After motility assessment at 72 h, nematodes were rinsed and incubated in water for 48 h, after which live and dead nematodes were counted. Nematodes were considered dead if they remained non-motile after probing with a picking needle. Nematode motility and mortality were significantly affected by the type of ITC, concentration and time of exposure. The number of non-motile nematodes increased with increasing concentration and time of exposure across all tested ITCs. The ED50 values (concentration required to cause 50% non-motility) of Allyl, 2-Phenylethyl and Benzyl were 37.4, 12.8 and 8.6 μg ml−1 after 24 h exposure. The ITC with potentially the greatest nematicidal effect was Benzyl (LD50 = 3.2 μg ml−1), followed by 2-Phenylethyl (LD50 = 5.2 μg ml−1), and Allyl (LD50 = 9.9 μg ml−1). The LD50 of all ITCs were not different from the ED50 after 72 h, meaning the effects of ITCs could be considered irreversible. This study suggests that brassica biofumigants that produce Benzyl, Allyl and 2-Phenylethyl ITCs are promising candidates for biofumigation of P. penetrans.

Characterization of finger millet extracts and evaluation of their nematicidal efficacy and plant growth promotion potential.

Plant-parasitic nematodes pose a significant threat to finger millet crops, potentially causing yield reduction of up to 70%. Extracts derived from finger millet varieties contain potent bioactive compounds that can mitigate nematode damage and promote plant growth. This study aimed at isolating and characterizing bioactive compounds from the finger millet varieties Ikhulule, Okhale-1, and U-15; evaluating the impact of Ikhulule and U-15 extracts on the mortality of the root lesion nematode Pratylenchus vandenbergae; assessing the growth promotion effects of Ikhulule and U-15 extracts on the finger millet variety Okhale-1; and determining the efficacy of these extracts in managing plant-parasitic nematodes under greenhouse conditions. Extracts were obtained from both leaves and roots and tested invitro for nematode mortality and invivo for growth promotion and nematode control. The results showed that finger millet extracts exhibited strong nematicidal properties invitro, achieving a mortality rate of up to 98% against P. vandenbergae nematodes. Applying these extracts to finger millet shoots significantly reduced nematode populations in both soil and roots and decreased the reproductive factor to below one (1), indicating an effective nematode control. The study attributes the enhanced nematicidal effects of finger millet extracts to their bioactive compounds, particularly dodecanoic acid, phytol, 1,1,4a-trimethyl-6-decahydro naphthalene, 2,3-dihydro-benzofuran, 2-methoxy-4-vinylphenol and ethyl ester, and hexadecanoic acid. These findings suggest that finger millet-derived extracts offer a natural solution for nematode management and broader agronomic benefits, ultimately contributing to overall plant health and productivity.

The New Nematicide Cyclobutrifluram Targets the Mitochondrial Succinate Dehydrogenase Complex in Bursaphelenchus xylophilus.

Bursaphelenchus xylophilus is a dangerous quarantine pest that causes extensive damage to pine ecosystems worldwide. Cyclobutrifluram, a succinate dehydrogenase inhibitor (SDHI), is a novel nematicide introduced by Syngenta in 2013. However, the nematocidal effect of cyclobutrifluram against plant-parasitic nematodes remains underexplored. Therefore, here, we aim to address this knowledge gap by evaluating the toxicity, effects, and mode of action of cyclobutrifluram on B. xylophilus. The result shows that cyclobutrifluram is the most effective agent, with an LC50 value of 0.1078 mg·L-1. At an LC20 dose, it significantly reduced the population size to 10.40 × 103 ± 737.56-approximately 1/23 that of the control group. This notable impact may stem from the agent's ability to diminish egg-laying and hatching rates, as well as to impede the nematodes' development. In addition, it has also performed well in the prevention of pine wilt disease, significantly reducing the incidence in greenhouses and in the field. SDH consists of a transmembrane assembly composed of four protein subunits (SDHA to SDHD). Four sdh genes were characterized and proved by RNAi to regulate the spawning capacity, locomotion ability, and body size of B. xylophilus. The mortality of nematodes treated with sdhc-dsRNA significantly decreased upon cyclobutrifluram application. Molecular docking further confirmed that SDHC, a cytochrome-binding protein, is the target. In conclusion, cyclobutrifluram has a good potential for trunk injection against B. xylophilus. This study provides valuable information for the screening and application of effective agents in controlling and preventing PWD in forests.

Anti-aging effect of peptides on Caenorhabditis elegans: a meta-analysis.

Recently, peptides have been studied in Caenorhabditis elegans for anti-aging research. Due to the lack of sufficient evidence, we conducted this meta-analysis focusing on the anti-aging effect of peptides in C. elegans to provide more convincing evidence. A literature search in PubMed, SCOUPUS, and Web of Science databases yielded 2879 articles. After removing duplicates and based on inclusion criteria and STAIR checklist quality assessment, nine articles were selected. Data extraction and analysis showed that, compared to the control group without peptide intervention, peptide supplementation significantly reduced nematode mortality risk [hazard ratio = 0.54, 95% confidence interval (CI) = 0.47, 0.62; P < 0.05], significantly increased the pharyngeal pumping rate [standardized mean difference (SMD) = 1.64, 95% CI = 0.87, 2.41; P < 0.05], bending frequency (SMD = 1.67, 95% CI = 1.16, 2.18; P < 0.05), and significantly decreased the accumulation of lipofuscin levels within nematodes (SMD = -4.48, 95% CI = -6.85, -2.12; P < 0.05). Additionally, subgroup analysis showed that doses ranging from 0.1 to 1 mg/mL (HR = 0.50, 95% CI = 0.38, 0.65; P < 0.05) displayed better anti-aging effects compared to other dose ranges. The findings suggest that peptides can significantly extend the lifespan of C. elegans under normal circumstances and improve three indicators of healthy life. More importantly, subgroup analysis revealed that a dosage of 0.1-1 mg/mL demonstrated superior anti-aging effects. This meta-analysis provides more convincing evidence that peptides can play an anti-aging role in C. elegans. © 2024 Society of Chemical Industry.

Exploiting fly ash as an ecofriendly pesticide/nematicide on Abesmoschus esculuntus: Insights into soil amendment-induced antioxidant fight against nematode mediated ROS

Conventional pest control measures, such as chemical pesticides and nematicides, have limited efficacy and raise environmental concerns, necessitating sustainable and eco-friendly alternatives for pest management. Therefore, to find a complementary eco-friendly pesticide/nematicide, this study investigated the role of fly ash (FA) in managing a notorious pest, Meloidogyne javanica and its impact on the growth and physiology of Abelmoschus esculentus. Molecular characterization using SSU and LSU rDNA gene markers confirmed the identity of Indian M. javanica as belonging to the same species. Biotic stress induced by nematode infection was significantly alleviated (P < 0.05) by FA application at a 20% w/v, regulating of ROS accumulation (44.1% reduction in superoxide anions and 39.7% reduction in hydrogen peroxide content) in the host plant. Moreover, FA enhanced antioxidant defence enzymes like superoxide dismutase (46.6%) and catalase (112%) to combat nematode induced ROS. Furthermore, the application of FA at a 20% concentration significantly improved the biomass and biochemical attributes of okra. Fly ash also upregulated the activity of the important osmo-protectant proline (11.5 μmol/g FW) to mitigate nematode stress in host cells. Suppression of disease indices like gall index and reproduction factor, combined with in-vitro experiments, revealed that FA exhibits strong nematode mortality capacity and thus can be used as a sustainable and eco-friendly control agent against root-knot nematodes.

Comprehensive analysis of Mentha longifolia subsp. himalaiensis essential oil: GC MS profiling and biological properties

Mentha longifolia is a well-known species of medicinal plant for its ethnopharmacological, pharmacological importance, industrial uses etc. This research paper presents a comprehensive study on a new species Mentha longifolia subsp. himalaiensis essential oil, focusing on its GC-MS analysis, nematicidal and antioxidant activities, as well as in-silico PASS prediction. The essential oil was extracted from Mentha longifolia subsp. himalaiensis leaves using steam distillation and subjected to gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) analysis to identify its chemical composition. The in vitro nematicidal activities were accessed via nematode mortality assay and nematode egg hatching assay against Meloidogyne incognita. The essential oil was also tested for its antioxidant activities via DPPH (2,2-diphenyl-2-picrylhydrazyl) radical scavenging activity, H2O2 (Hydrogen peroxide) scavenging activity and Metal chelating activity. The essential oil was also tested for antimicrobial potential against 5 strains of bacteria and two strains of fungus. Furthermore, the major chemical constituents of the essential oils were subjected to in-silico PASS prediction for their biological activities. The GC and GC-MS analysis revealed that piperitenone oxide (31.13 %) and cis-piperitone oxide (51.61 %) were the major components of the essential oil. The essential oil exhibited significant nematicidal activity against M. incognita and notable antioxidant activity. The essential oils also showed significant antibacterial and antifungal activity against targeted microbial strains. In-silico PASS prediction further supported the essential oil's bioactive properties and its potential for diverse applications. These results highlight the potential of Mentha longifolia subsp. himalaiensis essential oil as a natural nematicide, antimicrobial and antioxidant agent.

In vitro Evaluation of Rhizobacteria Isolated from Different Oilseed Growing Areas against Fusarium oxysporum f.sp. ricini and Rotylenchulus reniformis Infesting Castor

A study was conducted to evaluate the efficacy of 108 rhizobacterial isolates collected from different Oilseed rhizospheres against the wilt pathogen, Fusarium oxysporum f.sp. ricini and reniform nematode, Rotylenchulus reniformis under in vitro conditions. Among the 108 isolates tested, four isolates were reported to inhibit the radial growth of Fusarium oxysporum f.sp. ricini by more than 50% and caused more than 80% of juvenile (J4) mortality of reniform nematode. The effective rhizobacterial isolates were subjected to morphological and biochemical characterization for the assessment of plant growth promoting traits and bio-control properties.

Concurrent Infection of Oesophagostomum species in a Slaughtered Goat: A Case Report

The morbidity and mortality of gastrointestinal nematodes in goats made them one of the most significant parasites in the world, causing huge economic loss for farmers. It has been reported that the economic loss due to gastrointestinal parasitism was Rs. 372.35 per goat annually. In the present study, the intestinal sample was collected from a local slaughter house at Izatnagar, Bareilly, Uttar Pradesh, for screening the gastrointestinal nematodes. Initially, the pathological lesions like nodules, cyst and haemorrhagic patches etc. were examined for any parasitic infection. The found worms in the intestinal content were subjected for microscopic examination for the identification of the nematode and identified them as Oesophagostomum spp. based on buccal capsule with cephalic and cervical structures. Interestingly, both Oesophagostomum columbianum and O. asperum species were found in the same sample. The male and female Oesophagostomum species were also differentiated by examining the spicule and gubernacular length, position of the vulva and anus. This study reports the infection of Oesophagostomum spp. in a goat and the first case report of concurrent infection of O. columbianum and O. asperum in the Bareilly region of Uttar Pradesh.

Effects of Silver, Gold, and Platinum Nanoparticles on Selected Nematode Trophic Groups

Abstract As trophic organisms, nematodes play an essential role in the soil environment: they mineralize nutrients into plant-available forms, are a food source for other soil organisms, and feed on pathogenic organisms and plant pests, therefore regulating populations of soil microorganisms. The plant-parasitic nematodes are important pests of crops. Nanoparticles (NP) are increasingly used in agriculture and other production sectors. They are present in the soil, not necessarily in trace amounts, and can affect various soil organisms, including nematodes. In this article, the effects of silver (Ag), gold (Au), and platinum (Pt) nanoparticles on the mortality and reproduction activity of selected nematode species from two trophic groups: entomopathogenic nematodes (EPN) (Heterorhabditis bacteriophora and Steinernema feltiae) and plant parasitic nematodes (PPN) (Xiphinema diversicaudatum, Ditylenchus dipsaci, Heterodera schachtii) were studied under laboratory conditions. All nanoparticles decreased the nematode population to an extent depending on the nematode species, nanoparticle type, and exposure time. AgNP had the greatest nematicidal effect, except for AuNP, which reduced the population of H. schachtii the most. The greatest sensitivity to AgNP was observed in X. diversicaudatum (100% mortality), D. dipsaci (90% mortality), and 37 to 13% mortality in other species. Effect of AuNP and PtNP on entomopathogenic nematodes was comparable to the control, not treated with nanoparticles. AuNP and PtNP similarly influenced nematode mortality. However, the effect of nanoparticles on new generations of entomopathogenic nematodes developing in host larvae Galleria mellonella was inconclusive. All nanoparticles decreased the number of larvae of S. feltiae and increased the number of H. bacteriophora migrating outside the cadavers compared to the control.

Nematicidal Effect of Eupatorium odoratum Linn. Aqueous Extract on Burrowing Nematodes (Radopholus similis) and its Application to Control Toppling Disease on Cavendish Banana (Musa acuminata)

Abstract Radopholus similis (Cobb 1893) (Rhabditida, Pratylenchidae) is a common and destructive pest that causes significant yield losses in Cavendish bananas. The repeated use of synthetic pesticides to control this nematode has raised concerns about toxicity to users and the environment. An alternative approach to managing this harmful species involves the use of nontoxic plant-derived extracts that enhance protection against various biological constraints. In this study, aqueous extract from the leaves and stems of Eupatorium odoratum Linn. (EAEO) was used to control R. similis in banana roots under in vitro and on-plant conditions. Through direct contact and penetration experiments on roots, as well as on-plant trials, concentrations of 12500, 6250, 3120, 1560, and 780 mg DW·L−1 EAEO were used to evaluate nematode mortality rates, infection levels in root segments (in vitro experiment), root infection, root necrosis index, shoot and root fresh weight, and growth parameters such as stem length, diameter, leaf number, and leaf surface area (on-plant experiment). The results showed that the nematode mortality rate due to EAEO ranged from 35.3% to 90.1%, which is statistically significant compared to the mortality rate in the control treatment (16%). Significant nematode inhibition was observed in banana roots infected with R. similis and exposed to EAEO for 48 h. There were no statistically significant differences in root infection, root necrosis, and plant fresh weight between plants treated with fenamiphos and EAEO. Maximum effectiveness was observed at the 12500 mg DW·L−1 EAEO concentration. These findings provide valuable insights into the nematicidal metabolites of EAEO against R. similis. Thus, the potential of EAEO as a biocontrol agent against R. similis has been demonstrated. For future research, investigations will be extended to elucidate the mechanisms of action of the essential compounds in EAEO against nematodes, determine the optimal EAEO dosage for nematode control without harm to banana plants and the environment, assess the long-term effects of EAEO on banana plants and the environment, explore the ecological impact of EAEO use in agricultural ecosystems, study the effectiveness of EAEO on various plant species, and consider the development of commercial products or formulations based on EAEO.

Effect on Hatching and Mortality of Root-knot Nematode (Meloidogyne javanica) by Bio-agents

Investigations were carried out in vitro condition to evaluate the antagonistic effect of fungal and bacterial bio-agents. For effective management of root-knot nematode experiment was conducted in laboratory condition using the culture filtrate (5, 10 and 20 percent concentrate) of bio-agents (viz., Trichoderma viride, Trichoderma harzianum, Purpureocillium lilacinum, Pochonia chlamydosporia and Pseudomonas fluorescens). Experimental results showed that all the tested bio-agents significantly reduced the percent hatched juveniles and increased the percent mortality of juveniles. Among the tested bio-agents T. viride was found most effective treatment with minimum percent hatched juveniles and maximum percent mortality on eggs and juveniles of Meloidogyne javanica.

RICE SEED TREATMENTS BY SOAKING IN WATER AND THREE PESTICIDES (CARBOSULFAN, BENOMYL, AND IMIDACLOPRID) TO CONTROL FOLIAR NEMATODE Aphelenchoides besseyi

Aphelenchoides besseyi is one of the most important parasitic nematodes in rice plants, capable of dormancy in rice seeds. This study aims to determine the effects of soaking rice seeds in water and pesticides (carbosulfan, benomyl, and imidacloprid) on the mortality of A. besseyi, seed viability, and symptoms in rice seedlings. This study specifically used rice seeds infected with A. besseyi. Cold water treatment (cwt) at 5-10˚C for 24 hours followed by hot water treatment (hwt) at 52˚C for 10 minutes caused 51.17% A. besseyi mortality yet reduced the seed viability. Soaking the seed in the water at 25-30˚C for 24 hours followed by hwt at 57˚C for 10 minutes and hwt at 52˚C for 10 minutes could cause 48.67%, 39.18% and 33.05% nematode mortality, respectively. Low nematode mortality in all treatments (less than 60%) showed symptoms of A. besseyi infection in rice seedlings 21 days after planting. Seed dressing with imidacloprid 5WP (2% by seed weight) caused 47.25% A. besseyi mortality, whereas benomyl 50WP (0.2% by seed weight) and carbosulfan 25ST (2% by seed weight) caused only 27.61% and 11.34%. Based on two parameters (nematode mortality and seed viability), the most effective treatments were soaking the rice seeds in the water at 25-30˚C for 24 hours and seed dressing with imidacloprid.

Altitudinal variability in chemical profile and pesticidal properties of Zingiber roseum (Roxb.) Roscoe extracts

Plant extracts are considered as a promising alternative to chemical pest control agents. The chemistry of plant extracts varies with several environmental as well as geographical factors. Zingiber roseum (Roxb.) Roscoe also known as “Rosy Ginger” and “Jangli Adrak” is one of the most important aromatic and medicinal plant of family Zingiberaceae. The present study aimed to investigate the impact of altitude on the chemical composition, nematicidal and herbicidal activity of Z. roseum rhizome and seed extracts. The plants were collected from three different altitudes of Kumaun, Uttarakhand representing different environmental conditions. The extracts were prepared in acetone using cold percolation method. The compositional variation in chemical constituents of the extracts was determined by gas chromatography-mass spectrometry (GC–MS) analysis. The yield and chemical composition of extracts showed a significant altitudinal impact. Nematicidal activity of extracts was performed against Meloidogyneincognita. Results showed that the extracts exhibited significant nematode mortality irrespective of the altitudinal gradients. A significant correlation of altitudinal gradient was observed for the nematode egg hatchability reduction for the rhizome extracts. It was observed that plants growing at higher altitudes had better egg hatchability reduction (86.42 ± 2.30% at 1000 μg/mL after 96 h), compared with those growing at lower elevations. The herbicidal activity of rhizome and seed extracts was performed against radish and chicory seeds and the extracts showed different level of intensity of germination percentage, root and shoot length inhibition. In silico molecular docking was conducted to screen the nematicidal activity of major and potent compounds with the crystalline structure of Glutathione S-transferases (GSTs) of Caenorhabditis elegans and Wuchereria bancrofti, and Glutathione S-transferase-1 (GST-1) of M. incognita. Based on the current study, extract of Z. roseum may be regarded as potential nematicidal and herbicidal agents and may have potential application as botanicals.

Entomopathogenic Nematodes for Field Control of Onion Maggot (Delia antiqua) and Compatibility with Seed Treatments.

Onion maggot (Delia antiqua) is a prominent pest of allium crops in temperate zones worldwide. Management of this pest relies on prophylactic insecticide applications at planting that target the first generation. Because effective options are limited, growers are interested in novel tactics such as deployment of entomopathogenic nematodes. We surveyed muck soils where onions are typically grown to determine if entomopathogenic nematode species were present, and then evaluated the compatibility of entomopathogenic nematode species with the insecticides commonly used to manage D. antiqua. We also evaluated the efficacy of these entomopathogenic nematodes for reducing D. antiqua infestations in the field. No endemic entomopathogenic nematodes were detected in surveys of muck fields in New York. Compatibility assays indicated that, although insecticides such as spinosad and, to some extent, cyromazine did cause mortality of entomopathogenic nematodes, these insecticides did not affect infectivity of the entomopathogenic nematodes. Field trials indicated that applications of entomopathogenic nematodes can reduce the percentage of onion plants killed by D. antiqua from 6% to 30%. Entomopathogenic nematodes reduced D. antiqua damage and increased end of season yield over two field seasons. Applications of entomopathogenic nematodes may be a viable option for reducing D. antiqua populations in conventional and organic systems. Together with other management tactics, like insecticide seed treatments, applications of entomopathogenic nematodes can provide a yield boost and a commercially acceptable level of D. antiqua control.

Management of root-knot nematode [Meloidogyne incognita] in bhendi under pot culture condition using zero cost inputs

Bhendi scientifically known as Abelmoschus esculentus belongs to family Malvaceae and also known as Ladies Finger, Okra, Bhindi . It is the most important vegetable crop of the tropical and subtropical regions of the world. It belongs to the genus Abelmoschus and family Malvaceae. Okra is a multipurpose crop valued for its tender and delicious pods. In West Africa, leaves, buds, and flowers of okra are also consumed. The dried seeds provide oil, protein, vegetable curd, and a coffee additive or substitute. Okra dry seeds contain 18–20% oil and 20–23% crude protein. Foliage can be used for biomass, and the dried stems serve as a source of paper pulp or fuel. To a limited extent, okra is used in canned, dehydrated, or frozen forms. It has an average nutritive value of 3.21. It is commercially grown in India, Turkey, Iran, West Africa, Yugoslavia, Bangladesh, Afghanistan, Pakistan, West Bengal, Burma, Japan, Malaysia, Brazil, Ghana, Ethiopia, Cyprus, and the southern USA. Chitin has been extracted from various sources like prawn shells, crab shells, egg shells, jack fruit peel, garlic peel and onion peel. The efficacy of chitinase amendments on mortality of active juveniles of Meloidogyne incognita was estimated at various concentrations viz, 100%, 75%, 50% and 25% under three replications of 24 hours, 48 hours and 72 hours and assessment of plant morphometric characters, nematode mortality and root knot index under pot culture conditions.All the six chitinases amendments were tested in vitro to study the nematicidal action on Meloidogyne incognita. In treatment – concentration interaction, the highest nematode mortality (79.65 percent) was observed in Egg shell (100percent) followed by Crab shells (58.16 percent) Similar results were observed in 75, 50 and 25 per cent concentration of the amendments.Among the different chitinases amendments tested, Egg shell showed high degree of nematicidal effect against M. incognita in vitro and the lowest nematode mortality was recorded in onion peel (18.40) at 25 per cent concentration.Among the amendments tested, Egg shell treatment showed significant increase in root length and shoot length (40.22 cm 21.30 cm respectively) and the untreated control plants recorded the least root length and shoot length (19.11 cm and 21.30 ).All the treatments were found to reduce nematodes population in roots and highest reduction was noticed in egg shell treated plants (189.54 and 161.20) soil (250g) and root(5g) respectively.Significant reduction in root knot index (1.5) were observed in the treatment egg shell and carbofuran which recorded (1.0) per cent. The untreated control plant roots showed root knot index of 5.00 per cent.

Study on the characterization of pesticide modes of action similarity and the multi-endpoint combined toxicity of pesticide mixtures to Caenorhabditis elegans

With the widespread use of pesticides, the coexistence of multiple low-residue pesticides in environmental media has increased significantly, and the “cocktail” effect caused by this phenomenon has garnered increasing attention. However, owing to the scarcity of information regarding the modes of action (MOAs) of chemicals, the application of concentration addition (CA) models for evaluating and predicting the toxicity of mixture with similar MOAs is limited. Additionally, the joint toxicity laws of complex mixture systems to different toxicity endpoints in organisms remain unclear, and effective methods to test the mixture toxicity on lifespan and reproductive inhibition are lacking. Therefore, in this study, the similarity of pesticide MOAs was characterized using molecular electronegativity-distance vector (MEDV-13) descriptors based on eight pesticides (aldicarb, methomyl, imidacloprid, thiamethoxam, dichlorvos, dimethoate, methamidophos and triazophos). Additionally, the methods of lifespan and reproduction inhibition microplate toxicity analysis of elegans (EL-MTA and ER-MTA) were established to test the lifespan and reproduction inhibition toxicity of Caenorhabditis elegans. Finally, a unified scale synergistic-antagonistic heatmap (SAHscale) method was proposed to explore the combined toxicity of the mixtures on the lifespan, reproduction, and mortality of nematodes. The results showed that the MEDV-13 descriptors could effectively characterize the similarity in MOAs. The lifespan and reproductive ability of Caenorhabditis elegans were significantly inhibited when the pesticide exposure concentration was one order of magnitude lower than the lethal dose. The sensitivity of lifespan and reproductive endpoints to mixtures was dependent on the concentration ratio. The same rays in the mixture had consistent toxicity interactions on the lifespan and reproductive endpoints of Caenorhabditis elegans. In conclusion, we demonstrated the feasibility of MEDV-13 in characterizing the similarity of MOAs, and provided a theoretical basis for exploring the mechanism of chemical mixtures by studying their apparent toxicity of mixtures on nematode lifespan and reproduction endpoints.

Antifungal Properties of Hydrazine-Based Compounds against Candida albicans.

Candida albicans, an opportunistic yeast, is the most common cause of fungal infection. In the past decade, there has been an increase in C. albicans resistance to existing antifungal drugs, which has necessitated the development of new antifungal agents. In the present study, screening 60 compounds from the JUNIA chemical library enabled us to explore an additional 11 hybrid compounds that contain pyrrolidinone rings and hydrazine moieties for their potential antifungal activities. This chemical series was identified with fair to excellent antifungal activities. Among this series, three molecules (Hyd.H, Hyd.OCH3, and Hyd.Cl) significantly reduced C. albicans viability, with rapid fungicidal activity. In addition, these three compounds exhibited significant antifungal activity against clinically isolated fluconazole- or caspofungin-resistant C. albicans strains. Hyd.H, Hyd.OCH3, and Hyd.Cl did not show any cytotoxicity against human cancer cell lines up to a concentration of 50 µg/mL and decreased Candida biofilm formation, with a significant reduction of 60% biofilm formation with Hyd.OCH3. In an infection model of Caenorhabditis elegans with C. albicans, hydrazine-based compounds significantly reduced nematode mortality. Overall, fungicidal activity was observed for Hyd.H, Hyd.OCH3, and Hyd.Cl against C. albicans, and these compounds protected C. elegans from C. albicans infection.

Glucosinolate-extracts from residues of conventional and organic cultivated broccoli leaves (Brassica oleracea var. italica) as potential industrially-scalable efficient biopesticides against fungi, oomycetes and plant parasitic nematodes

This study aimed to standarize a protocol for obtaining a bioactive extract from broccoli (Brassica oleracea var. italica) crop residues, that is suitable for application on an industrial scale and effective in reducing plant disease incidence. For this purpose, the influence of several extraction factors in the glucosinolate (GSL) content was studied with leaves collected from two conventional broccoli fields and two organic broccoli fields. The analysis showed that lyophilization had no influence on the GSL content. Storage of plant material under two different temperatures (− 20ºC and − 80ºC) had no influence on the GSLs content of the extracts. Phytotoxicity of the extracts was studied with six different plant seeds, and also cytotoxicity was determined with human liver cells in vitro. The extracts were phytotoxic at dilutions above 10%, while cell toxicity was low. Extracts concentrations of 0.1%, 1% and 2% were tested in vitro against eight plant pathogenic fungi and two oomycetes in solid and in liquid media. The extracts reduced the growth of several plant pathogenic fungi at 2% dilution by up to 38.37% against Alternaria alternata and up to 46.55% against Sclerotinia sclerotiorum. When combined with myrosinase enzyme the effect of the extracts was enhanced, reaching inhibition values of 67.06% against A. alternata in solid medium and 68.52% against Rhizoctonia solani in liquid medium. In contrast, the same extracts increased the growth of the plant pathogenic oomycetes Pythium ultimum and Phytophthora cactorum. The effect of the same extracts in the free leaving larvae, J2s, of the plant-parasitic nematode (PPN) Meloidogyne javanica was not obvious. Minor significant differences were obtained but with no clear dose-response in nematode mortality, and no inhibition of eggs hatching was observed. These results show the industrial potential of using broccoli residues to obtain extracts with biopesticide activity against plant pathogenic fungi.

Nematocidal and Bactericidal Activities of Green Synthesized Silver Nanoparticles Mediated by Ficus sycomorus Leaf Extract.

Nanoparticles effectively control most plant pathogens, although research has focused more on their antimicrobial than their nematocidal properties. This study synthesized silver nanoparticles (Ag-NPs) through a green biosynthesis method using an aqueous extract of Ficus sycomorus leaves (FS-Ag-NPs). The nanoparticles were characterized using SEM, TEM, EDX, zeta sizer, and FTIR. The TEM results showed that the synthesized NPs were nanoscale and had an average particle size of 33 ± 1 nm. The elemental silver signal at 3 keV confirmed the formation of Ag-NPs from an aqueous leaf extract of F. sycomorus. The FTIR analysis revealed the existence of several functional groups in the prepared Ag-NPs. The strong-broad band detected at 3430 cm-1 indicated the stretching vibration of -OH (hydroxyl) and -NH2 (amine) groups. The nematocidal activity of biosynthesized FS-Ag-NPs has been evaluated in vitro against the root-knot nematode Meloidogyne incognita at 24, 48, and 72 h. The FS-Ag-NPs at a 200 µg/mL concentration applied for 48 h showed the highest effectiveness, with 57.62% nematode mortality. Moreover, the biosynthesized FS-Ag-NPs were also tested for their antibacterial activity against Pectobacterium carotovorum, P. atrosepticum, and Ralstonia solanacearum. With the application of nanoparticles, the reduction in bacterial growth gradually increased. The most potent activity at all concentrations was found in R. solanacearum, with values of 14.00 ± 2.16, 17.33 ± 2.05, 19.00 ± 1.41, 24.00 ± 1.41, and 26.00 ± 2.83 at concentrations of 5, 10, 15, 20, and 25 µg/mL, respectively, when compared with the positive control (Amoxicillin 25 µg) with a value of 16.33 ± 0.94. At the same time, the nanoparticles showed the lowest reduction values against P. atrosepticum when compared to the control. This study is the first report on the nematocidal activity of Ag-NPs using F. sycomorus aqueous extract, which could be a recommended treatment for managing plant-parasitic nematodes due to its simplicity, stability, cost-effectiveness, and environmentally safe nature.