Nematicidal Action Research Articles

Phytochemistry of isolated essential oils from Cautleya spicata (Sm.) Baker for their pesticidal evaluation and in-silico approaches to reveal the mode of nematicidal action

Phytochemistry of isolated essential oils from <i>Cautleya spicata</i> (Sm.) Baker for their pesticidal evaluation and <i>in-silico</i> approaches to reveal the mode of nematicidal action

Evaluation of the nematicidal and enzymatic activity of Pleurotus djamor on Trichostrongylus spp. and Strongyloides papillosus

ABSTRACT Parasitic gastrointestinal nematodes (GINs) cause diseases that are a major challenge to livestock production. Chemical control is the most widely used method, but it has many economic and environmental problems. This study was to evaluate in vitro the nematicidal and enzymatic activity of Pleurotus djamor against Trichostrongylus spp., and Strongyloides papillosus. The fungus was cultivated in a solid medium composed of wheat seeds for 25 days. The enzyme extraction was then performed using distilled water in the ratio of 1:5. Subsequently, by means of filtration and then centrifugation, the cell-free crude extract (CFCE) was obtained. Proteolytic activity was measured at pH 5 using the caseinolytic assay. The nematophagous assay of the P. djamor on the infective larvae (L3) was performed for 6 h. The nematicidal effect of the CFCE (active and denatured) was analysed over a period of 48 h. The CFCE showed proteolytic activity of 8.9 ± 0,5 U mL−1. P. djamor reduced the number of L3 by 75% (p < 0.01). The active CFCE showed a statistical difference compared to the control and the denatured (p < 0.01). On the other hand, there was no significant difference between the denatured group and the control group (without enzymes). The percentage reduction of L3 was 57%. This result suggests that the nematicidal action occurred mainly due to the activity of the proteases present in the CFCE. This study reports for the first time the applicability of proteases produced by P. djamor in the biochemical control of GINs, which could become an alternative biopesticide in the future.

Nematicidal activity and action mode of a methyl-accepting chemotaxis protein from Pseudomonas syringae against Caenorhabditis elegans

The conventional phytopathogen Pseudomonas syringae reportedly possesses several virulence determinants against Caenorhabditis elegans; however, their action mechanisms remain elusive. This study reports the nematicidal activity and action receptor of a methyl-accepting chemotaxis protein (MCP03) of a wild-type P. syringae MB03 against C. elegans. Purified MCP03 exhibited nematicidal toxicity against C. elegans at a half-lethal concentration of 124.4 μg mL−1, alongside detrimental effects on the growth and brood size of C. elegans. Additionally, MCP03-treated worms exhibited severe pathological destruction of the intestine and depressed wrinkles of the cuticle. Yeast two-hybrid assays identified a subunit of COP9 signalosome, namely CSN-5, which functioned as an MCP03 action receptor. In vitro pull-down verified the binding interaction between MCP03 and CSN-5. RNA interference assays confirmed that MCP03 antagonizes CSN-5, thereby adversely affecting the brood size and cuticle integrity of C. elegans. Following MCP03 infection, the expression of genes related to reproduction, growth, and cuticle formation, such as kgb-1, unc-98, and col-117, was considerably downregulated, indicating pathological changes in MCP03-treated nematodes. Therefore, we proposed that MCP03 antagonizes CSN-5, causing lethality as well as detrimental effects on the fertility, growth, and morphogenesis of C. elegans, which can provide new insights into the signaling pathways and mechanisms underlying the nematicidal action of MCP03 toward C. elegans.

Linking the protease activity to the nematicidal action of edible mushroom.

Biological control using edible mushrooms as natural enemies is a sustainable alternative for pest management. Despite the well-established literature on toxins and secondary metabolites produced by these fungi in the biochemical control of nematodes, the nematicidal activity of proteases from different Pleurotus species is yet to be investigated. Therefore, this study aimed to correlate protease to the nematicidal activity of different mushrooms, Pleurotus sp., P. ostreatus (SB), P. ostreatus (Pearl), and P. djamor. For such a purpose, we performed motility assays of Panagrellus sp. at different time intervals, 6, 12, and 24h for each of the mushrooms. In addition, the protease activity was measured using different pH (5, 7, and 9) and fermentation time intervals (45 and 75 days). Furthermore, we also evaluated the effect of this cell-free extract on Panagrellus sp. In response to these experiments, all edible mushrooms showed a reduction over 82% for the nematode-feeding activity (p < 0.01). The cell-free crude extract of each of the fungi studied showed nematocidal activity (p < 0.01). For the 45-day fermentation, P. djamor exhibited statistical significance (p < 0.01) compared with the others, reaching a reduction percentage of 73%. For the 75-day fermentation, Pleurotus sp. and P. ostreatus (Pearl) showed significant differences compared with the other fungi (p < 0.01), with reduction percentages of 64 and 62%, respectively. Herein, protease activity was associated with the nematicidal action of different Pleurotus species in controlling Panagrellus sp.

Enzyme production by the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae and their application in the control of nematodes (Haemonchus spp. and Meloidogyne incognita) in vitro

Brazil is affected by the infection of gastrointestinal nematodes (Haemonchus spp.) because it causes subclinical diseases in small ruminants that directly affect weight and milk production and, in turn, generate a health risk for the animals. In the same way root-knot nematodes (Meloidogyne incognita) is a serious disease, which parasitize the roots of tomato plants causing damage such as poor nutrient absorption leading to significant yield losses. In order to minimize the economic impact of these nematodes, it is important to establish new control strategies. Beauveria bassiana and Metarhizium anisopliae are two main mycoinsecticides used to control many orders of insects, such as Lepidoptera and Hemiptera. These fungi have the ability to produce extracellular enzymes, which play an important role to control in the pest infection process. The aim of this study was to evaluate the production of proteases and chitinases by the entomopathogenic fungi B. bassiana and M. anisopliae on different solid and liquid culture media and their application in vitro to the control of Haemonchus spp and Meloidogyne incognita. To achieve this goal, enzymes were produced under solid and liquid fermentation conditions to determine the highest chitinolytic and proteolytic activity of commercial two strain of B. bassiana (IBCB 66 and ESALQ PL63) and M. anisopliae (IBCB 425 and ESALQ E9) in liquid media: SDY broth, YPG culture medium, synthetic, and soluble starch with yeast extract. The solid media tested were: rice supplemented with whey and chrysalis flour mixed with rice. In addition, the nematicidal action of their extracts (containing concentrated enzymes and without fungal cells) was measured. The results showed that the best culture medium (p< 0.01) for protease was solid serum rice medium, with a value for M. anisopliae IBCB 425 of 52 U/mg, and for B. bassiana ESALQ PL63 the value was 36 U/mg, compared to all the tested media. On the other hand, for chitinase of M. anisopliae strain IBCB 425, the activity value was close to 0.60 U/mg. In contrast, for B. bassiana isolate ESALQ PL63, SDY medium was the best inducer for chitinase production, with a value of 0.90 U/mg. Regarding the nematicidal activity of the crude extracts, the reduction percentages were 58% for ESALQ PL63 and 100% for IBCB 425 in the case of animal parasites. For plant parasites, the reduction percentages were 19% for ESALQ PL63 and 71% for IBCB 425. Thus, the use of enzyme-rich crude extracts presents promising control options for pest control.

METHOD OF ASSESSING THE NEMATOCIDAL EFFECTIVENESS OF A BIOPREPA-RATION BASED ON PREDATORY MICROMYCETE AGAINST THE POTATO STEM NEMATODE

Aim – Studing of methods for determining the effectiveness of Nematophagin BT against potato stem nematode in the laboratory. Materials and methods. For the experiment, potato tubers with signs of damage by the stem nematode Ditylenchus destructor Thorne, 1945 were selected. The method of treatment of cut potato tubers with the preparation was used. It was compared with the method of treatment of whole tubers in the laboratory. The effect of the microbiological nematicidal preparation (Nematofagin BT) developed by ITI Biotechnology of NAAS was determined. The effectiveness of the microbiological preparation of nematicidal action (Nematofagin BT), developed by ITI Biotechnology of NAAS, was determined. The active ingredient of the drug is a microscopic fungus-predator Arthrobotrys oligospora strain 12, the initial culture of which is deposited in the collection of microorganism cultures of the D.K. Zabolotny Institute of Microbiology and Virology of the National Academy of Sciences of Ukraine F100047. Results. The methods of laboratory evaluation of the nematicidal effect of the biological product against potato stem nematode are described. In laboratory conditions, to determine the effectiveness of the drug, it is more informative to use cut tubers that have been infected with stem nematode. This method requires much more time to set up, but the bioagent has bigger accessibility to the pest. The use of whole tubers is less labor-intensive, but there is a possibility of using uninfected material in the experiment. The expediency of using these methods in laboratory conditions for the selection of active strains and determination of their effectiveness is shown. Conclusion. The method of nematicidal treatment of cut tubers with established infection of stem nematode is more informative than the use of whole tubers. It is advisable to analyze for damage to potatoes by nematodes when using pieces of affected potatoes from 3 to 7 days after treatment with a 3% solution of the biological product with an exposure of 5 hours. In laboratory conditions, both methods of treatment of cut and whole tubers with the preparation can be used to test the effect of Nematophagin BT on potato stem nematode. Nematophagin BT showed nematicidal activity against potato stem nematode in laboratory conditions.

Antibacterial peptides from Monochamus alternatus induced oxidative stress and reproductive defects in pine wood nematode through the ERK/MAPK signaling pathway

Pine wilt disease is a devastating disease of pine caused by the pine wood nematode (PWN) Bursaphelenchus xylophilus. Long-term use of chemical nematicides leads to the development of resistance in nematodes and harms the environment. Evaluations for green environmental protection agents, identified the antibacterial peptide, MaltDef1, from Monochamus alternatus which had nematicidal effect. We studied its nematicidal activity and action against PWN. In this study, the antibacterial peptide S-defensin was synthesized from M. alternatus. The results showed that S-defensin caused mortality to the PWN, causing shrinkage, pore, cell membrane dissolution and muscle atrophy. In addition, PWN reproduction was also affected by S-defensin; it decreased in a concentration dependent manner with increasing treatment concentration. By contrast, reactive oxygen species (ROS) in vivo increased in a concentration-dependent manner. We applied transcriptome to analyze the changes in gene expressions in S-defensin treated PWN, and found that the most significantly enriched pathway was the ERK/MAPK signaling pathway. RNAi was used to validate the functions of four differential genes (Let-23, Let-60, Mek-2 and Lin-1) in this pathway. The results showed that knockdown of these genes significantly decreased the survival rate and reproductive yield of, and also increased ROS in PWN. The antibacterial peptide S-defensin had a significant inhibitory effect on the survival and reproduction of PWN, shown by cell membrane damage and intracellular biological oxidative stress via regulating the ERK/MAPK signaling pathway. This indicates that S-defensin has a target in B. xylophilus, against which new green target pesticides can be developed.

Antagonistic Bacteria Bacillus velezensis VB7 Possess Nematicidal Action and Induce an Immune Response to Suppress the Infection of Root-Knot Nematode (RKN) in Tomato.

Meloidogyne incognita, the root-knot nematode (RKN), a devastating plant parasitic nematode, causes considerable damage to agricultural crops worldwide. As a sedentary root parasite, it alters the root's physiology and influences the host's phytohormonal signaling to evade defense. The sustainable management of RKN remains a challenging task. Hence, we made an attempt to investigate the nematicide activity of Bacillus velezensis VB7 to trigger the innate immune response against the infection of RKN. In vitro assay, B. velezensis VB7 inhibited the hatchability of root-knot nematode eggs and juvenile mortality of M. incognita by 87.95% and 96.66%, respectively at 96 hrs. The application of B. velezensis VB7 challenged against RKN induced MAMP-triggered immunity via the expression of transcription factors/defense genes by several folds pertaining to WRKY, LOX, PAL, MYB, and PR in comparison to those RKN-inoculated and healthy control through RT-PCR. Additionally, Cytoscape analysis of defense genes indicated the coordinated expression of various other genes linked to immune response. Thus, the current study clearly demonstrated the effectiveness of B. velezensis VB7 as a potential nematicide and inducer of immune responses against RKN infestation in tomato.

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.

Ipomoea carnea associated phytochemicals and their in silico investigation towards Meloidogyne incognita

ABSTRACT Root-knot nematodes (Meloidogyne spp.) are sedentary endo-parasite that causes severe yield loss in carrot. Chemical nematicides currently used to manage Meloidogyne incognita are being phased out because of rising health and environmental issues. This study aimed to evaluate nematicidal effect of various concentrations, viz., 250, 500, 750, 1000ppm of leaf extract of Ipomoea carnea against M. incognita infecting carrot under in vitro and in pots assays. In our result, all tested concentrations displayed J2s mortality and egg hatching inhibition along with improving growth of carrot and reduced J2s population and root-knot index. Molecular docking performed predicts binding interactions of two major compounds, viz., neophytadiene and 2-amino-2-methyl-1-propanol as shown by GC-MS analysis with targeted protein, odorant response gene-1 of M. incognita, to confirm nematicidal action of I. carnea leaf extract. The obtained results also suggested that neophytadiene interacted more and strongly bound with odorant response gene-3 than 2-amino-2-methyl-1-propanol. The biochemical ligand-target protein interaction described in the present work will be helpful in the logical selection of biomolecules and essential proteins. Therefore, plant extract may be used the best alternative to chemical nematicides to control root-knot nematodes and caused longitudinal growth of the plant as well as reduce environmental risks.

Nematicidal activity of Brazilian honeys

In Brazil, there is a great cultural and social diversity, which leads to the use of several natural products due to their ethnopharmacological properties, incluing honey. Honey is a nutrient-rich food that has several beneficial activities, such as: anti-inflammatory, antioxidant, antimicrobial and nematicidal actions. However, there are no studies regarding the nematicidal effect of honeys from Brazil. Thus, the objective of this study was to evaluate the nematicidal action of honeys of Apis mellifera L. from orange, avocado, eucalyptus, multifloral and honey from Tetragonisca angustula species (known as Jataí) on Panagrellus sp. nematodes. In the nematicidal assays, solutions of these honeys were used in concentrations of 3; 1.5; 0.75 and 0.5% (w/v). The control group contained only distilled water. In assays with a concentration of 0.5% of avocado honey and T. angustula bee honey, a significant reduction was demonstrated, compared to the control group (respectively: 41.4% and 47.2%). The results obtained demonstrated, for the first time, that A. mellifera L. honey from avocado flowering and T. angustula honey showed significant nematicidal activity against juveniles of the free-living nematode model Panagrellus sp. Therefore, further studies on the compositions of these honeys must be developed.

Bacillus VOCs in the Context of Biological Control

A contemporary agricultural production system relying on heavy usage of agrochemicals represents a questionable outlook for sustainable food supply in the future. The visible negative environmental impacts and unforeseen consequences to human and animal health have been requiring a shift towards the novel eco-friendly alternatives for chemical pesticides for a while now. Microbial-based biocontrol agents have shown a promising potential for plant disease management. The bacteria of the genus Bacillus have been among the most exploited microbial active components due to several highly efficient mechanisms of action against plant pathogens, as well as a palette of additional plant-beneficial mechanisms, together with their suitable properties for microbial biopesticide formulations. Among other bioactive metabolites, volatile organic compounds (VOCs) have been investigated for their biocontrol applications, exhibiting the main advantage of long-distance effect without the necessity for direct contact with plants or pathogens. The aim of this study is to give an overview of the state-of-the-art in the field of Bacillus-based VOCs, especially in terms of their antibacterial, antifungal, and nematicidal action as the main segments determining their potential for biocontrol applications in sustainable agriculture.

Phytochemical Screening and Evaluation of Pesticidal Efficacy in the Oleoresins of Globba sessiliflora Sims and In Silico Study.

Globba sessiliflora Sims is an aromatic rhizomatous herb of family Zingiberaceae which is endemic to Peninsular India. This study first reports the phytochemical profile and pesticidal potential of oleoresins obtained from the aerial and rhizome parts of Globba sessiliflora Sims. The oleoresins were prepared by the cold percolation method and were analyzed by a gas chromatography-mass spectrometry (GC-MS) method. Both the oleoresins varied greatly in composition, the major compounds identified in aerial part oleoresin (GSAO) were methyl linoleate, methyl palmitate, and phytol, while the major compounds present in rhizome part oleoresin (GSRO) were γ-sitosterol, 8 (17),12-labdadiene-15, 16-dial, methyl linoleate, and methyl palmitate. In order to evaluate the biological activities, the oleoresins were tested under laboratory conditions for nematicidal action and inhibition of egg hatching potential against root knot nematode, where GSRO was more effective. Insecticidal activity was performed against mustard aphid, Lipaphis erysimi and castor hairy caterpillar, Selepa celtis. In case of mustard aphid, GSRO (LC50 = 154.8 ppm) was more effective than GSAO (LC50 = 263.0 ppm), while GSAO (LC50 = 346.7.0 ppm) was more effective against castor hairy caterpillar than GSRO (LC50 = 398.1 ppm). The herbicidal activity was performed in the receptor species Raphanus raphanistrum subsp. sativus, and the oleoresins showed different intensities for seed germination inhibition and coleoptile and radical length inhibition. Molecular docking studies were conducted to screen the in vitro activities and through molecular docking, it was found that the major oleoresins components were able to interact with the binding pocket of HPPD and AChE with γ-sitosterol showing the best binding affinity.

Elucidation of the nematicidal mode of action of grammicin on Caenorhabditis elegans

Grammicin (Gra) is derived from the endophytic fungus Xylaria grammica EL000614 and shows nematicidal activity against the devastating root-knot nematode Meloidogyne incognita in-vitro, in planta, and in-field experiments. However, the mechanism of the nematicidal action of Gra remains unclear. In this study, Gra exposure to the model genetic organism Caenorhabditis elegans affected its L1, L2/3, L4, and young adult stages. In addition, Gra treatment increased the intracellular reactive oxygen species (ROS) levels of C. elegans and M. incognita. Molecular docking interaction analysis indicated that Gra could bind and interact with GCS-1, GST-4, and DAF-16a in order of low binding energy, followed by SOD-3, SKN-1, and DAF-16b. This implies that the anthelmintic action of Gra is related to the oxidative stress response. To validate this mechanism, we examined the expression of the genes involved in the oxidative stress responses following treatment with Gra using transgenic C. elegans strains such as the TJ356 strain zIs356 [daf-16p::daf-16a/b::GFP + rol-6 (su1006)], LD1 ldIs7 [skn-1p::skn-1b/c::GFP + rol-6 (su1006)], LD1171 ldIs3 [gcs-1p::GFP + rol-6 (su1006)], CL2166 dvIs19 [(pAF15) gst-4p::GFP::NLS], and CF1553 strain muIs84 [(pAD76) sod-3p::GFP + rol-6 (su1006)]. Gra treatment caused nuclear translocation of DAF-16/FoxO and enhanced gst-4::GFP expression, but it had no change in sod-3::GFP expression. These results indicate that Gra induces oxidative stress response via phase II detoxification without reduced cellular redox machinery. Gra treatment also inhibited the nuclear localization of SKN-1::GFP in the intestine, which may lead to a condition in which oxidative stress tolerance is insufficient to protect C. elegans by the inactivation of SKN-1, thus inducing nematode lethality. Furthermore, Gra caused the mortality of two mutant strains of C. elegans, CB113 and DA1316, which are resistant to aldicarb and ivermectin, respectively. This indicates that the mode of action of Gra is different from the traditional nematicides currently in use, suggesting that it could help develop novel approaches to control plant-parasitic nematodes.

MARIGOLD BIOPESTICIDE AS AN ALTERNATIVE TO CONVENTIONAL CHEMICAL PESTICIDES

Marigold (Tagetes spp) which is considered to be a traditional medicinal plant, has significant therapeutic value and is used in treatment of a number of ailments. This review mainly emphasizes on the role of Tagetes as biopesticides especially as insecticide, mosquitocide, nematicide, bactericide and fungicide. The essential oils obtained from the aerial part of Tagetes mainly contain monoterpene hydrocarbons (ocimenes, limonene, terpinene etc) and acyclic monoterpene ketones (tagetones, dihydrotagetone and tagetenone) in addition to lower amount of sesquiterpene and oxygenated compounds. These components are mainly responsible for insecticidal, larvicidal and mosquitocidal property. On the other hand species of Tagetes also show strong nematicidal effect .Thus they can be used to suppress nematode species in the field by different techniques such as crop rotation or intercropping system or by exterting allelopahic effect. Tagetes can show a remarkable biochemical interaction known as allelopathy by producing a potentially bioactive component α-therthienyl that is mainly responsible for nematicidal action. This sulphur containing compound has nematicidal, insecticidal, fungicidal, antiviral and cytotoxic effect. The essential oil of Tagetes also shows strong bactericidal and fungicidal effect against a number of plant pathogenic bacteria and fungi. This review not only discusses the role of marigold as biopesticides especially as insecticides, mosquitocides, nematicides, bactericides and fungicide but also elucidates its ecofriendly potential to be used in the agricultural field as an alternative to chemical synthetic pesticides.

Identification of chemical components from essential oils and aqueous extracts of some medicinal plants and their nematicidal effects on Meloidogyne incognita

BackgroundEssential oils from aerial parts of Achillea wilhelmsii, Tanacetum polycephalum and Teucrium polium were isolated by using Clevenger-type apparatus and tested at different concentrations for their nematicidal activity against the second stage juvenile (J2) of Meloidogyne incognita in vitro condition. The chemical components of the essential oils and seed extracts of each plant (0.2 g) were extracted with maceration with methanol/acetic acid mixture (85:15, v/v). Analysis was done by Gas Chromatography, GC-Mass Spectrometry) and HPLC. Identified chemical components were tested after this on J2 of M. incognitain. Nuclear magnetic resonance spectroscopy was done to investigate the properties of organic molecules by drawing their spectrum using Broker AVANCE AQS-300 MHz.ResultsSignificant difference was achieved on nematicidal activity of essential oils based on the plant species and oil concentrations. GC and GC–MS led to identification of 41, 39 and 45 major compounds from T. polium, T. polycephalum and A. wilhelmsii oils, respectively. A number of 10 components with different ranges of percentage were recorded in all of the tested plants oils. Use of HPLC resulted in identification of 4, 3 and 2 chemical compounds in the extracts of A. wilhelmsii, T. polycephalum and T. polium, respectively. The nematicidal activity of commercial polyphenols at the concentration of 1100 ppm showed 58.3, 48.9, 28.2 and 26.8 percentages J2 mortalities by catechin, coumarin, gallic acid and chlorogenic, respectively. Nematotoxicity test of commercial terpenoids showed the highest J2 mortalities (more than 80%), in concentrations of 100 and 200 ppm limonene, β-pinene and α-pinene. However, it was less than 30% of J2 mortality caused by terpinen-4-ol, α-terpineol and linalool.ConclusionsCompounds such as Limonene, β-pinene and α-pinene were detected in all of the tested plants, A. wilhelmsii, T. polycephalum and T. polium, having an effective nematicidal action versus terpinen-4-ol, α-terpineol and linalool.

Local Bacillus species as potential biocontrol agents for Meloidogyne enterolobii in melon (Cucumis melo L.)

ABSTRACT Biological control is an environmentally safe alternative in the management of nematodes. The selection of new biocontrol agents has focused on the potential of Bacillus species in in vitro and in vivo studies. In this study, twenty-three local Bacillus isolates were characterised and evaluated for metabolisable carbon source, secondary metabolite production and nematicidal action. The in vitro antagonism studies were evaluated after direct confrontation between infecting juveniles of M. enterolobii and bacterial isolates. In a greenhouse, nematicidal activity was evaluated 51 days after nematode inoculation in melon plants previously inoculated with the bacteria and cultivated in pots. The numbers of egg masses, galls, J2 and eggs in the root, J2 in the soil, the reproduction factor and the biomass yield of the plants were evaluated. From the results obtained in the laboratory experiments, it was observed that five carbon sources (D-glucose, N-acetyl-glucosamine, D-maltose, malic acid and trisodium citrate) were common to all isolates, with variation in the production of secondary metabolites. The sum of nematostatic and nematicidal effects was above 90%. In the pot experiment, a significant reduction in the number of galls was observed with the treatments LCB 03, LCB 40, LCB 45, LCB 47, LCB 51, LCB 56 and LCB 5(3) and there was no increase in plant biomass. Root protection may be associated with effective colonisation through biofilm formation and the action of metabolites with nematicide and disorientation action. However, it is necessary to carry out further studies.

Nematicidal and Molecular Docking Investigation of Essential Oils from Pogostemon cablin Ecotypes against Meloidogyne incognita.

Root-knot nematode, Meloidogyne incognita is one of the most destructive nematodes worldwide. Essential oils (EOs) are being extensively utilized as eco-benign bionematicides, although the precise mechanism of action remains unclear. Pogostemon cablin Benth. is well-known as "Patchouli". It is native to South East Asia and known for ethno-pharmacological properties. In this study, chemical composition and potential nematicidal effect of EOs hydrodistilled from the leaves of P. cablin grown at three different locations in India were comprehensively investigated to correlate their mechanism of action for target specific binding affinities toward nematode proteins. Aromatic volatile Pogostemon essential oils (PEO) from Northern India (PEO-NI), Southern India (PEO-SI) and North Eastern India (PEO-NEI) were analyzed by Gas Chromatography-Mass Spectrometry (GC/MS) to characterize forty volatile compounds. Maximum thirty-three components were identified in PEO-NEI. Sesquiterpenes were predominant with higher content of α-guaiene (2.3-24.4 %), patchoulol (6.1-32.7 %) and α-bulnesene (5.9-27.1 %). Patchoulol was the major component in PEO-SI (32.7±1.2 %) and PEO-NEI (29.2±1.1 %), while α-guaiene in PEO-NI (24.4±1.2 %). In vitro nematicidal assay revealed significant nematicidal action (LC50 44.6-87.0 μg mL-1 ) against juveniles of M. incognita within 24 h exposure. Mortality increases with increasing time to 48 h (LC50 33.6-71.6 μg mL-1 ) and 72 h (LC50 27.7-61.2 μg mL-1 ). Molecular modelling and in silico studies revealed multi-modal inhibitive action of α-bulnesene (-22 to -13 kJ mol-1 ) and α-guaiene (-22 to -12 kJ mol-1 ) against three target proteins namely, acetyl cholinesterase (AChE), odorant response gene-1 (ODR1), odorant response gene-3 (ODR3). Most preferable binding mechanism was observed against AChE due to pi-alkyl, pi-sigma, and hydrophobic interactions. Structure nematicidal activity relationship suggested the presence of hydroxy group for nematicidal activity is nonessential, rather highly depends on synergistic composition of sesquiterpene hydrocarbons.

A Comprehensive in vitro and in silico Analysis of Nematicidal Action of Essential Oils.

Nematicidal potential of essential oils (EOs) has been widely reported. Terpenoids present in most of the essential oils have been reported responsible for their bioactivity though very less is known about their modes of action. In the present study, an in vitro screening of nine Eos, namely, Citrus sinensis (OEO), Myrtus communis (MTEO), Eucalyptus citriodora (CEO), Melaleuca alternifolia (TEO), Acorus calamus (AEO), Commiphora myrrha (MREO), Cymbopogon nardus (CNEO), Artemisia absinthium (WEO), and Pogostemon cablin (PEO) against Meloidogyne incognita revealed OEO, CNEO, and TEO as most effective with LC50 39.37, 43.22, and 76.28 μg ml–1 respectively. EOs had varying compositions of mono- and sesquiterpenes determined by gas chromatography-mass spectrometry (GC-MS) analysis. The in silico molecular interactions screening of major EO constituents and the seven selected target proteins of the nematode indicated highest binding affinity of geraniol-ODR1 (odorant response gene 1) complex (ΔG = -36.9 kcal mol–1), due to extensive H-bonding, hydrophobic and π-alkyl interactions. The relative binding affinity followed the order: geraniol-ODR1 > β-terpineol-ODR1 > citronellal-ODR1 > l-limonene-ODR1 > γ-terpinene-ODR1. Taken together, the cumulative in vitro and computational bioefficacy analysis related to the chemoprofiles of EOs provides useful leads on harnessing the potential of EOs as bionematicides. The insight on biochemical ligand–target protein interactions described in the present work will be helpful in logical selection of biomolecules and essential oils for development of practically viable bionematicidal products.

БИОЛОГИЧЕСКИЙ КОНТРОЛЬ ФИТОПАРАЗИТИЧЕСКИХ НЕМАТОД НА ОСНОВЕ МИКРООРГАНИЗМОВ (ОБЗОР)

Phytoparasitic nematodes are dangerous pests of agricultural crops. Annually, yield losses due to damage by phytonematodes are up to 15%, which is estimated at billions of dollars. The aim of the research is to summarize and analyze scientific publications concerning the harmfulness of phytoparasitic nematodes and microorganisms that have an antagonistic effect against them for the further development of biopreparations of nematicidal action based on antagonist bacteria. The study objectives are to identify the most common groups of nematodes, review the information concerning microorganisms that have a nematicidal effect and biological products based on them. The review considers the main representatives of nematodes – plant parasites and notes their habitat, harmfulness, affected crops and symptoms of infection. Brief descriptions of life cycles and systematic affiliation are given. Analysis of scientific publications on the studied topic shows that numerous microorganisms are capable of exhibiting nematicidal activity, directly or indirectly affecting nematodes in the soil. In the course of the analysis of literary sources, it was found that both fungi and bacteria can exhibit an antagonistic effect against phytoparasitic nematodes. It is noted that for both groups of microorganisms, there are several mechanisms of action: predation, parasitism, competition, etc. It has been found that fungi and bacteria synthesize metabolites of various natures with a nematicidal effect: toxins, lytic enzymes, antibiotics, siderophores. It should be noted that microorganisms-antagonist are capable of exhibiting nematicidal activity to nematodes of different stages of the life cycle: eggs, juveniles and adults. Nowadays, some commercial preparations based on antagonist microorganisms are successfully used in agriculture in different countries. During the analysis, it was discovered that to date, few viruses are capable of infecting nematodes; their systematic affiliation has also been established. It is noted that, if compared to bionematicides based on fungi and bacteria, not a single bionematicide based on viruses has been developed. The development of bionematicides based on antagonist microorganisms is a promising area but requires further studies of interactions in the plant-nematode-microorganism system.