Combinatorial in vitro RNAi of two neuropeptide genes and a pharyngeal gland gene on Meloidogyne incognita

Root-knot nematodes are the most economically important group of plant-parasitic nematodes. In the present study, functional validation using in vitro RNAi was carried out on Meloidogyne incognita with two FMRFamide-like peptide genes, flp-14 and flp-18, and a subventral pharyngeal gland specific gene, 16D10. It was found that RNAi silencing of each gene reduced the attraction of M. incognita at different time intervals both in combination and individually. Silencing of the genes reduced nematode infection by 23-30% and development as indicated by a reduction in the number of females by 26-62%. Reproduction was decreased by 27-73% and fecundity was decreased by 19-51%. In situ hybridisation revealed the expression of flp-18 in cells associated with the ventral and retro vesicular ganglia of the central nervous system. qRT-PCR supported the correlation between phenotypic effects of silencing with that of transcript quantification.

Download Full-text

Activity of Saponins from Medicago Species against Phytoparasitic Nematodes

Plants ◽

10.3390/plants9040443 ◽

2020 ◽

Vol 9 (4) ◽

pp. 443 ◽

Cited By ~ 2

Author(s):

Trifone D’Addabbo ◽

Maria Pia Argentieri ◽

Jerzy Żuchowski ◽

Elisa Biazzi ◽

Aldo Tava ◽

...

Keyword(s):

Meloidogyne Incognita ◽

In Vitro Assays ◽

Parasitic Nematodes ◽

Plant Parasitic Nematodes ◽

Phytoparasitic Nematodes ◽

Phytochemical Profile ◽

Medicago Species ◽

Phytoparasitic Nematode ◽

Plant Parasitic

Content of bioactive saponins of Medicago species suggests that they may also exert, as previously demonstrated on M. sativa, nematicidal properties exploitable for the formulation of new products for sustainable phytoparasitic nematode management. This study was addressed to highlight the bioactivity of saponins from five different Medicago species still poorly known for their biological efficacy, i.e., M. heyniana, M. hybrida, M. lupulina, M. murex and M. truncatula, against the plant parasitic nematodes Meloidogyne incognita, Xiphinema index and Globodera rostochiensis. The bioactivity of the extracts from the five Medicago species was assessed by in vitro assays on the juveniles (J2) and eggs of M. incognita and G. rostochiensis and the adult females of X. index. The suppressiveness to M. incognita of soil treatments with the Medicago plant biomasses was also investigated in a tomato experiment. The nematicidal activity of the five Medicago species was reported and discussed in relation to their phytochemical profile.

Download Full-text

Toxicity of ethanol solutions and vapours against Meloidogyne incognita

Nematology ◽

10.1163/15685411-00003046 ◽

2017 ◽

Vol 19 (3) ◽

pp. 271-280 ◽

Cited By ~ 6

Author(s):

Julio C.P. Silva ◽

Vicente P. Campos ◽

Eduardo S. Freire ◽

Willian C. Terra ◽

Liliana E. Lopez

Keyword(s):

Root System ◽

Meloidogyne Incognita ◽

Parasitic Nematodes ◽

Infested Soil ◽

Large Reduction ◽

Plant Parasitic Nematodes ◽

Second Stage ◽

Plant Parasitic

Ethanol (EtOH) is less harmful to humans than currently available nematicide molecules. This study evaluated the efficacy of EtOH in controlling Meloidogyne incognita in vitro and in lettuce plants under glasshouse conditions. Aqueous EtOH solutions (5-70% volume) and their vapours caused an acute nematicidal effect in vitro in second-stage juveniles (J2) of M. incognita and reduced hatching of J2. There was a large reduction of galls and eggs in the root system when 40 ml of EtOH was applied to M. incognita-infested soil at concentrations of 40 and 70%. Water exposed to EtOH vapours for 1 h became toxic, and a 12-h exposure caused 100% J2 mortality. Use of a plastic cover did not increase the efficiency of EtOH in controlling M. incognita in lettuce plants. The observed EtOH effects indicate its prospective use in controlling plant-parasitic nematodes, especially in glasshouses.

Download Full-text

Identification and in situ and in vitro characterization of secreted proteins produced by plant-parasitic nematodes

Parasitology ◽

10.1017/s0031182000067640 ◽

1996 ◽

Vol 113 (6) ◽

pp. 589-597 ◽

Cited By ~ 17

Author(s):

R. H. C. Curtis

Keyword(s):

Parasitic Nematodes ◽

Plant Parasitic Nematodes ◽

Root Cells ◽

Feeding Site ◽

In Vitro Characterization ◽

Plant Nematode ◽

Plant Parasitic

SUMMARYSecretions of plant-parasitic nematodes which are released into plant tissue may play critical roles in plant-nematode interactions. The identification and characterization of these molecules are of fundamental importance and may help to facilitate the development of novel strategies to interfere with nematode infection of plants and thereby decrease nematode-induced damage to crops. An antibody-based approach was used to isolate molecules present on the nematode surface and in nematode secretions. Monoclonal antibodies (MAbs) were produced to secretions and to whole Heterodera avenue 2nd-stage juveniles; several of these MAbs recognized molecules present in nematode secretions produced in vitro. Three of these molecules have been partly characterized in H. avenae, Globodera rostochiensis, G. pallida and Meloidogyne incognita. A MAb reacting with the surfaces of these nematodes recognized antigens of different molecular weight in each of the species tested. This difference in antigenicity might be related to specific functions in these nematodes. Preliminary results show that this antibody also localized the antigen in root cells surrounding the feeding site induced by M. incognita in Arabidopsis thaliana.

Download Full-text

Behavioural response of Meloidogyne incognita to benzyl isothiocyanate

Nematology ◽

10.1163/138855409x12465362560674 ◽

2009 ◽

Vol 11 (4) ◽

pp. 603-610 ◽

Cited By ~ 7

Author(s):

Inga A. Zasada ◽

Edward P. Masler ◽

John M. Halbrendt ◽

Stephen T. Rogers

Keyword(s):

Meloidogyne Incognita ◽

Plant Material ◽

Egg Production ◽

Parasitic Nematodes ◽

Plant Parasitic Nematodes ◽

Benzyl Isothiocyanate ◽

Treatment Groups ◽

Dose Dependent ◽

Sublethal Concentrations

Abstract The breakdown of brassicaceous plant material produces nematotoxic isothiocyanates (ITCs). However, after the incorporation of brassicaceous plant material into soil, many nematodes are likely to be exposed only to sublethal concentrations of these compounds. Although unknown, the effect of these low ITC concentrations on the behaviour of plant-parasitic nematodes could play a role in nematode suppression. To address this question, the behaviour of infective second-stage juveniles (J2) of Meloidogyne incognita was evaluated following in vitro exposure to sublethal concentrations of benzyl isothiocyanate (BITC). Behaviour was qualitatively and quantitatively affected. Overall nematode activity in treatment groups scored visually, and individual nematode movement frequencies, quantified by video assay, were each significantly reduced within 2 h of exposure to 0.01 mM BITC. All responses were dose dependent. Infectivity of BITC-treated J2 of M. incognita on soybean (Glycine max) was measured directly by root staining and gall rating, and indirectly by egg production. All experiments showed significantly reduced infectivity after treatment of J2 with 0.01 mM BITC. In addition, egg production was almost completely eliminated (<5% of control) by 0.03 mM BITC. The correlation between the effect of BITC concentrations on J2 activity and infectivity was positive, with decreased J2 activity and infectivity resulting in decreased egg production. BITC concentrations that do not cause mortality significantly affect the behaviour of M. incognita J2, indicating that sublethal concentrations contribute to the overall nematode suppression by brassicaceous green manures.

Download Full-text

Nematicidal activity of the tropane alkaloids hyoscyamine and scopolamine against the root-knot nematode Meloidogyne incognita

Nematology ◽

10.1163/15685411-bja10074 ◽

2021 ◽

pp. 1-9

Author(s):

Djaafar Babaali ◽

Johannes Roeb ◽

Sabri Zaidat ◽

Bouchra Reguige ◽

Miloud Hammache ◽

...

Keyword(s):

Meloidogyne Incognita ◽

Tropane Alkaloids ◽

Datura Stramonium ◽

Nematicidal Activity ◽

Crop Damage ◽

Parasitic Nematodes ◽

Plant Parasitic Nematodes ◽

Root Knot Nematode ◽

Hyoscyamine And Scopolamine

Summary Alkaloids and alkaloid-producing plants have the potential to reduce crop damage by plant-parasitic nematodes. In a series of in vitro experiments, the nematicidal activity of the tropane alkaloids, hyoscyamine and scopolamine, and a mixture of both on the root-knot nematode, Meloidogyne incognita, was tested. Solutions of 16 mg of compound per ml of solvent were used in concentrations of 80-1280 μg ml−1 of water. Inactivity of second-stage juveniles of M. incognita increased with increasing concentration and exposure time. Lethal concentrations (LC50) after 120 min of exposure ranged from 182.4 μg ml−1 for scopolamine to 318.4 μg ml−1 for hyoscyamine and 332.8 μg ml−1 for the combination of both alkaloids. Similarly, the same concentrations of scopolamine inhibited hatching of M. incognita to a greater extent than hyoscyamine. In a glasshouse experiment, M. incognita was not able to penetrate the roots, induce galls and reproduce on Datura stramonium, D. innoxia and D. tatula. Results indicate that the tropane alkaloids hyoscyamine and scopolamine contained in Datura plants express a strong nematicidal activity against M. incognita and could possibly be used for an alternative and sustainable nematode management.

Download Full-text

Activities of essential oils from three Brazilian plants and benzaldehyde analogues against Meloidogyne incognita

Nematology ◽

10.1163/15685411-00003276 ◽

2019 ◽

Vol 21 (10) ◽

pp. 1081-1089 ◽

Cited By ~ 1

Author(s):

Aline Ferreira Barros ◽

Vicente Paulo Campos ◽

Denilson Ferreira de Oliveira ◽

Fabiola de Jesus Silva ◽

Iselino Nogueira Jardim ◽

...

Keyword(s):

Essential Oils ◽

Meloidogyne Incognita ◽

Parasitic Nematodes ◽

Plant Parasitic Nematodes ◽

Plant Essential Oils ◽

Hyptis Suaveolens ◽

Stage Juvenile ◽

Main Component

Summary There is a demand for novel products for the control of plant-parasitic nematodes, so we characterised the effectiveness of some plant essential oils against Meloidogyne incognita and verified the efficiency of the major component from the most toxic oils and their analogues using in vitro and in vivo assays. In this study, the essential oils from Piptadenia viridiflora, Hyptis suaveolens and Astronium graveolens against M. incognita were evaluated, but only P. viridiflora oil showed toxicity toward M. incognita. Benzaldehyde was its main component according to GC-MS analysis. In in vitro assays, benzaldehyde (100 and 200 μg ml−1) and its oxime (400 μg ml−1) caused a higher rate of M. incognita second-stage juvenile (J2) mortality than the nematicide carbofuran (170 μg ml−1). Reductions of more than 90% in the number of galls and eggs, even greater than that observed with carbofuran, were observed in the assay where the J2 were placed in solutions of benzaldehyde and its oxime 48 h prior to tomato plant inoculation. Application of benzaldehyde together with M. incognita J2 to the substrate resulted only in a reduction in the number of eggs (42-65%); however, its oxime reduced both the number of galls (43-84%) and eggs (23-89%). Therefore, the P. viridiflora oil, its major component benzaldehyde, and the analogue benzaldehyde oxime are toxic to M. incognita. In two different in vivo assays, benzaldehyde oxime was confirmed as toxic to M. incognita with a greater efficacy than benzaldehyde.

Download Full-text

Activity of Hydroxamic Acids from Secale cereale Against the Plant-Parasitic Nematodes Meloidogyne incognita and Xiphinema americanum

Phytopathology ◽

10.1094/phyto-95-1116 ◽

2005 ◽

Vol 95 (10) ◽

pp. 1116-1121 ◽

Cited By ~ 20

Author(s):

I. A. Zasada ◽

S. L. F. Meyer ◽

J. M. Halbrendt ◽

C. Rice

Keyword(s):

Secale Cereale ◽

Meloidogyne Incognita ◽

Degradation Products ◽

Hydroxamic Acids ◽

Parasitic Nematodes ◽

Plant Parasitic Nematodes ◽

Egg Hatch ◽

Starting Point ◽

Plant Parasitic

Cyclic hydroxamic acids are secondary metabolites found in the family Poaceae and have been implicated in the allelopathy of rye (Secale cereale). The toxicity of these compounds against plant-parasitic nematodes is unknown. DIBOA (2,4-dihydroxy-(2H)-1,4-benzoxazin-3(4H)-one), DIMBOA (2,4-hydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one), and their degradation products BOA (benzoxazolin-2(3H)-one) and MBOA (6-methoxy-benzoxazolin-2(3H)-one) were screened in vitro against Meloidogyne incognita second-stage juveniles (J2) and eggs and mixed-stages of Xiphinema americanum. Xiphinema americanum was more sensitive to DIBOA and DIMBOA than M. incognita J2, with a maximum apparent mortality of 96 and 92% compared to 73 and 72% at 90 μg/ml. Eggs of M. incognita were less sensitive to the hydroxamic acids than J2; only DIBOA resulted in a 50% reduction in egg hatch, with a lethal concentration (LC50) of 74 μg/ml compared to 21 μg/ml for J2. When M. incognita J2 were exposed to DIBOA for 48 h and the compound was removed and replaced with water, the LC50 value increased from 21.0 to 40.7 μg/ml. MBOA was not toxic to X. americanum or M. incognita eggs, but was toxic to M. incognita J2, with LC50 values of 44 and 20 μg/ml before and after the compound was removed and replaced with water. BOA was the least toxic hydroxamic acid tested; it did not reduce M. incognita egg hatch after 1 week of exposure or increase X. americanum mortality after 24 h of exposure. While in vitro studies provide a valuable starting point in determining the toxicity of the chemical component of rye, the relevance of the data to soil remains to be determined.

Download Full-text

Allelopathy: a possible mechanism of suppression of plant-parasitic nematodes by entomopathogenic nematodes

Nematology ◽

10.1163/156854199508766 ◽

1999 ◽

Vol 1 (7) ◽

pp. 735-743 ◽

Cited By ~ 32

Author(s):

Parwinder S. Grewal ◽

Edwin E. Lewis ◽

Sudha Venkatachari

Keyword(s):

Meloidogyne Incognita ◽

Entomopathogenic Nematodes ◽

Galleria Mellonella ◽

Steinernema Feltiae ◽

Symbiotic Bacteria ◽

Parasitic Nematodes ◽

Plant Parasitic Nematodes ◽

Tomato Roots ◽

Xenorhabdus Nematophilus ◽

Plant Parasitic

Abstract A possible mechanism of suppression of a plant-parasitic nematode Meloidogyne incognita by entomopathogenic nematodes is described. Heat-killed entomopathogenic nematodes Steinernema feltiae and S. riobrave temporarily suppressed penetration of the root-knot nematode M. incognita into tomato roots, but live nematodes had no effect. Infective juvenile M. incognita were repelled from all entomopathogenic nematode treatments that included their symbiotic bacteria. They were repelled by Galleria mellonella cadavers infected with S. carpocapsae, S. feltiae, and S. riobrave and from cell-free culture filtrates of the symbiotic bacteria Xenorhabdus nematophilus, X. bovienii, and Xenorhabdus sp. "R" from the three nematode species, respectively. Cell-free filtrates from all three Xenorhabdus spp. were toxic to M. incognita infective juveniles causing 98-100% mortality at 15% concentration. Cell-free filtrate of Xenorhabdus sp. "R" also reduced the hatch of M. incognita eggs. Application of formulated bacterial cell-free filtrates temporarily suppressed M. incognita penetration into tomato roots in a greenhouse trial. The short-term effects of cell-free bacterial filtrates, namely toxicity and repellency, were almost entirely due to ammonium. These results demonstrate allelopathic interactions between plant-parasitic nematodes, entomopathogenic nematodes and their symbiotic bacteria. The likely role of allelopathy in the suppression of plant-parasitic nematodes by innundative applications of entomopathogenic nematodes is discussed. Allelopathie: Ein moglicher Mechanismus zur Unterdruckung pflanzenparasitarer Nematoden durch insektenpathogene Nematoden - Es wird ein moglicher Mechanismus zur Unterdruckung des pflanzenparasitaren Nematoden Meloidogyne incognita durch insektenpathogene Nematoden beschrieben. Durch Hitze abgetotete insektenpathogene Nematoden Steinernema feltiae und S. riobrave underdruckten das Eindringen des Wurzelgallenalchens M. incognita in Tomatenwurzeln, lebende Nematoden hatten keine Wirkung. Infektionsjuvenile von M. incognita wurden von allen Behandlungen mit insektenpathogenen Nematoden abgestossen, die auch die symbiontischen Bakterien einschlossen. Sie wurden durch die Kadaver von Galleria mellonella abgestossen, die mit S. carpocapsae, S. feltiae und S. riobrave infiziert waren sowie durch zellfreie Kultursubstrate der symbiontischen Bakterien Xenorhabdus nematophilus, X. bovienii und Xenorhabdus sp. "R" aus den drei genannten Nematodenarten. Zellfreie Kultursubstrate von allen drei Xenorhabdus spp. waren giftig fur die Infektionsjuvenilen von M. incognita und verursachten in einer Konzentration von 15% Abtotungsraten von 98-100%. Zellfreie Kultursubstrate von Xenorhabdus sp. "R" vermiderten ausserdem das Schlupfen von M. incognita-Eiern. In einem Gewachshausversuch unterdruckten formulierte zellfreie Bakterienfiltrate vorubergehend das Eindringen von M. incognita in Tomatenwurzeln. Die Kurzzeitwirkungen von zellfreien Bakterien filtraten, namentlich Giftigkeit und Abstossung, waren nahezu ganz bedingt durch Ammoniak. Diese Ergebnisse zeigen das Vorhandensein von allelopathischen Wechselwirkungen zwischen pflanzenparasitaren Nematoden, insektenpathogenen Nematoden und deren symbiontischen Bakterien. Die wahrscheinliche Rolle von Allelopathie bei der Unterdruckung pflanzenparasitarer Nematoden durch eine Massenanwendung insektenpathogener Nematoden wird diskutiert.

Download Full-text

Short-Term Effects of Sublethal Doses of Nematicides on Meloidogyne incognita

Phytopathology ◽

10.1094/phyto-11-18-0420-r ◽

2019 ◽

Vol 109 (9) ◽

pp. 1605-1613 ◽

Cited By ~ 10

Author(s):

Catherine L. Wram ◽

Inga A. Zasada

Keyword(s):

Population Density ◽

Meloidogyne Incognita ◽

Cultivated Plants ◽

Parasitic Nematodes ◽

Initial Population ◽

Plant Parasitic Nematodes ◽

Water Control ◽

Effective Doses ◽

Sublethal Doses ◽

Plant Parasitic

Meloidogyne species are one of the most important groups of plant-parasitic nematodes globally because of their ability to damage most cultivated plants. Although they are widespread and economically important, there are limited control measures to combat these nematodes. New nonfumigant nematicides have been discovered that have the potential to be widely utilized for the management of plant-parasitic nematodes. Because of the longer half-lives in soil and lower toxicity of new nematicides compared with traditional fumigant and nonfumigant nematicides, understanding how nematodes respond to sublethal doses of nematicides is imperative to understanding whether nematicide resistance has the potential to develop. Characterizing responses of nematodes to sublethal doses will provide the foundation for future work, such as gene expression studies. In this study, the nematicides oxamyl (Vydate), fluazaindolizine (Salibro), fluensulfone (Nimitz), and fluopyram (Velum), were evaluated to understand how sublethal doses affect the fecundity and mobility of Meloidogyne incognita second-stage juveniles (J2). Using a microwell assay system, dose-response curves for each nematicide were established for M. incognita J2. Fluopyram was the most toxic nematicide, with effective doses up to 230 times lower than that of other nematicides. The other nematicides had predicted ED50 values (effective doses that resulted in 50% of the population becoming inactive) of 89.4, 131.7, and 180.6 ppm for oxamyl, fluensulfone, and fluazaindolizine, respectively. The 24-h ED50 of each nematicide was then used in both motility and infectivity assays. The motility and activity of M. incognita J2 exposed to ED50 doses of fluazaindolizine and fluensulfone was significantly reduced, with nematodes initially being motile but eventually becoming inactive. However, the motility of M. incognita J2 exposed to ED50 doses of fluopyram and oxamyl was not different from a water control. In a pot assay, M. incognita J2 exposed to ED50 doses of fluazaindolizine, oxamyl, and fluensulfone were unable to reproduce on tomato, with reproduction factors (RF = final population density/initial population density) of 0 to 0.03. Fluopyram did not reduce reproduction of M. incognita, with a mean RF of 38.7 ± 4.5, which was similar to the RF of 46.3 ± 4.6 for the water control. This study is the first comprehensive evaluation of M. incognita activity, motility, and fecundity after exposure to the traditional nematicide, oxamyl, as well as three new nematicides, fluazaindolizine, fluopyram, and fluensulfone.

Download Full-text

Biological attributes of Salibro™, a novel sulfonamide nematicide. Part 2: Impact on the fitness of various non-target nematodes

Nematology ◽

10.1163/15685411-bja10041 ◽

2020 ◽

pp. 1-17 ◽

Cited By ~ 1

Author(s):

Tim C. Thoden ◽

Mariam A. Alkader ◽

John A. Wiles

Keyword(s):

Negative Impact ◽

Soil Health ◽

Agar Plate ◽

Parasitic Nematodes ◽

Published Data ◽

Plant Parasitic Nematodes ◽

Free Living ◽

Plant Parasitic ◽

Novel Products

Summary Currently a renaissance in chemical nematicides is taking place with novel products like Nimitz® (a.s. fluensulfone), Velum Prime® (a.s. fluopyram) and Salibro™ (a.s. fluazaindolizine – Reklemel™ active) entering the marketplace. Although a considerable amount of published data is already available on their laboratory and field impact on plant-parasitic nematodes, little is understood of their compatibility with the beneficial or free-living nematodes that are part of the soil health network. In a range of laboratory studies, the effects of these nematicides on the vitality and reproduction of several species was tested, including both cosmopolitan free-living nematodes (Acrobeloides, Cruznema, Panagrobelus) as well as commercially applied entomopathogenic nematodes (Steinernema, Heterorhabditis). Within aqueous exposure and agar plate in vitro assays, species sensitivity to those nematicides differed significantly but their fitness (vitality and reproduction; infectivity to insect hosts) was generally not adversely impacted by concentrations of 5-50 ppm (a.s.) of Salibro. Even at 250 ppm (a.s.) of Salibro only some species of the bacterial-feeding species showed some negative impact. By contrast, both Nimitz at 50 ppm (a.s.) and Velum at 5 ppm (a.s.) consistently demonstrated stronger adverse impacts. In second level soil drenching assays, either no, or occasionally slight, adverse effects on the natural community of free-living nematodes were observed if soils were drenched with different volumes of Salibro at 5-50 ppm (a.s.), while relatively stronger reductions were measured within the plant-parasitic species (especially root-knot nematodes). Both Nimitz and Vydate (a.s. oxamyl) showed some degree of compatibility at 5 and 25 ppm (a.s.), respectively, which was generally higher than for Velum Prime at 5 ppm (a.s.). Overall, these data indicate that, when used at common field rates, Salibro will be one of the best options as part of integrated nematode management programmes where the use of chemical nematicides is required.

Download Full-text