Morphological, Molecular and Ecological Characterization of a Native Isolate of Steinernema Feltiae (Rhabditida: Steinernematidae) From Southern Chile

Abstract Background: Steinernema feltiae is an entomopathogenic nematode used in biological control programs with a global distribution. It has been shown that populations of S. feltiae may have phenotypic plasticity derived from local adaptation and may vary in different traits, such as location and penetration of the host. This is the first time that a Chilean isolate has been described in detail, taking into account morphological, molecular and ecological characteristics. Methods: S. fealtiae was detected a few years ago in southern regions of Chile in the town Lican Ray and was morphologically and morphometrically described, along with a molecular description based on the ITS and D2-D3 regions. Some ecological characteristics were determined, including the temperature requirements for completion of its life cycle and the effect of three water levels in soil for optimal reproduction. Results: Morphometric characteristics of different life stages show large intraspecific variability in averages and ranks compared with isolates from different geographical origins. The molecular data also show intraspecific variability with respect to other isolates. The lower, optimal and higher temperatures found to limit the infestation and reproduction of Galleria mellonella were 10, 20 and 30 °C respectively, and emergence from the host larvae occurred approximately ten days after inoculation. Differences were observed in offspring emerging from the host, and the 120 infective juveniles (IJ)/larvae dose was the most prolific at 20 °C. The water content of the soil did not affect the number of infective juvenile invaders, penetration efficacy (%), and time of emergence of the IJ or offspring per larvae, but it caused a delay in achieving full mortality at the permanent wilting point with respect to saturation and field capacity.Conclusions: Data obtained in this study are valuable since they outline some environmental requirements of this strain to perform optimally in the event of being used as a soil pest bioantagonist.

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Sex and the dynamics of infection in the entomopathogenic nematode Steinernema feltiae

Journal of Helminthology ◽

10.1017/s0022149x00015911 ◽

1997 ◽

Vol 71 (3) ◽

pp. 197-202 ◽

Cited By ~ 12

Author(s):

D.A. Bohan ◽

W.M. Hominick

Keyword(s):

Sex Ratio ◽

Entomopathogenic Nematodes ◽

Galleria Mellonella ◽

Entomopathogenic Nematode ◽

Steinernema Feltiae ◽

Infective Juvenile ◽

Infective Stage ◽

Male And Female ◽

Per Capita ◽

Infection Interaction

AbstractAn infection experiment was conducted to assess the change in the proportions of Steinernema feltiae Filipjev (Site 76 strain) infective juveniles becoming male or female on exposure to the test host Galleria mellonella L. Using a mathematical model for the infection interaction, the per capita probability of penetration per unit time (transmission coefficient), for those juveniles becoming male or female, and the magnitude of the male and female classes in the infective juvenile pool were estimated. The results show that S. feltiae infective juveniles which subsequently become female have a greater probability of invasion into test hosts than their male counterparts, which leads to markedly female biased sex ratios during the initial stages of the infection interaction. As the infection progresses, however, it was found that the sex ratio became balanced. This was because the underlying sex ratio in the infective stage pool was balanced. The implications of this dynamism in the sex ratio of the entomopathogenic nematodes are discussed with respect to the infection interaction, transmission and the likely environment in which the infective juveniles reside.

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Long-term dynamics of infectiousness within the infective-stage pool of the entomopathogenic nematode Steinernema feltiae (Site 76 strain) Filipjev

Parasitology ◽

10.1017/s0031182096008426 ◽

1997 ◽

Vol 114 (3) ◽

pp. 301-308 ◽

Cited By ~ 19

Author(s):

D. A. BOHAN ◽

W. M. HOMINICK

Keyword(s):

Population Structure ◽

Time Course ◽

Galleria Mellonella ◽

Entomopathogenic Nematode ◽

Steinernema Feltiae ◽

Infective Juvenile ◽

Future Research ◽

Infection Model ◽

Ecological Implications

Infection experiments were conducted to assess the proportion of Steinernema feltiae (Site 76 strain) Filipjev infective juveniles which penetrated into the test host Galleria mellonella L. over an 8-week period. Using a combined ANOVA and infection model approach, the analyses showed that the proportion of infective juveniles which penetrated into the test hosts changed significantly over time. This change was found to be consistent with a fluctuation in the size of a non-infectious population structure within the infective juvenile pool. These fluctuations in the magnitude of the infectious structure would dynamically alter the number of juveniles available for infection in hosts and so impose the observed change in the proportion of juveniles penetrating into hosts, over the 8-week time-course. The empirical and ecological implications of such a dynamically limited pattern of infection and possible future research into the mechanisms responsible for the non-infectious population structure are discussed.

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Transcriptional variation and divergence of host-finding behaviour in Steinernema carpocapsae infective juveniles

BMC Genomics ◽

10.1186/s12864-019-6179-y ◽

2019 ◽

Vol 20 (1) ◽

Cited By ~ 1

Author(s):

Neil D. Warnock ◽

Deborah Cox ◽

Ciaran McCoy ◽

Robert Morris ◽

Johnathan J. Dalzell

Keyword(s):

Galleria Mellonella ◽

Entomopathogenic Nematode ◽

Gene Families ◽

Nematode Species ◽

Host Finding ◽

Steinernema Carpocapsae ◽

Differentially Expressed ◽

Infective Juvenile ◽

Neuronal Genes ◽

Sodium Transporter

Abstract Background Steinernema carpocapsae is an entomopathogenic nematode that employs nictation and jumping behaviours to find potential insect hosts. Here we aimed to investigate the transcriptional basis of variant host-finding behaviours in the infective juvenile (IJ) stage of three S. carpocapsae strains (ALL, Breton and UK1), with a focus on neuronal genes known to influence behaviour in other nematode species. Identifying gene expression changes that correlate with variant host-finding behaviours will further our understanding of nematode biology. Results RNA-seq analysis revealed that whilst up to 28% of the S. carpocapsae transcriptome was differentially expressed (P < 0.0001) between strains, remarkably few of the most highly differentially expressed genes (> 2 log2 fold change, P < 0.0001) were from neuronal gene families. S. carpocapsae Breton displays increased chemotaxis toward the laboratory host Galleria mellonella, relative to the other strains. This correlates with the up-regulation of four srsx chemosensory GPCR genes, and a sodium transporter gene, asic-2, relative to both ALL and UK1 strains. The UK1 strain exhibits a decreased nictation phenotype relative to ALL and Breton strains, which correlates with co-ordinate up-regulation of neuropeptide like protein 36 (nlp-36), and down-regulation of an srt family GPCR gene, and a distinct asic-2-like sodium channel paralogue. To further investigate the link between transcriptional regulation and behavioural variation, we sequenced microRNAs across IJs of each strain. We have identified 283 high confidence microRNA genes, yielding 321 predicted mature microRNAs in S. carpocapsae, and find that up to 36% of microRNAs are differentially expressed (P < 0.0001) between strains. Many of the most highly differentially expressed microRNAs (> 2 log2 fold, P < 0.0001) are predicted to regulate a variety of neuronal genes that may contribute to variant host-finding behaviours. We have also found evidence for differential gene isoform usage between strains, which alters predicted microRNA interactions, and could contribute to the diversification of behaviour. Conclusions These data provide insight to the transcriptional basis of behavioural variation in S. carpocapsae, supporting efforts to understand the molecular basis of complex behaviours in nematodes.

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Intraspecific variation among isolates of the entomopathogenic nematode Steinernema feltiae from Bull Island, Ireland

Nematology ◽

10.1163/156854109x447015 ◽

2009 ◽

Vol 11 (3) ◽

pp. 439-451 ◽

Cited By ~ 4

Author(s):

Martin Downes ◽

Conor Meade ◽

Stephen Boyle ◽

Alec Rolston ◽

Thomae Kakouli-Duarte

Keyword(s):

Intraspecific Variation ◽

Galleria Mellonella ◽

Insect Pests ◽

Entomopathogenic Nematode ◽

Laboratory Culture ◽

Steinernema Feltiae ◽

Host Insect ◽

Large Numbers ◽

Insect Mortality ◽

Control Insect

AbstractThe application of large numbers of entomopathogenic nematodes (EPN) to control insect pests of agriculture is likely to have an impact on the local EPN fauna, yet little is known about the intraspecific relationships between EPN populations, particularly with regard to phylogeny and outbreeding. Here we assess the fitness, with regards to fecundity, host insect mortality and time taken to produce progeny, of isolates of Steinernema feltiae from Bull Island, Ireland. Exon-primed, intron-crossing (EPIC) PCR was used to examine intraspecific phylogenies between S. feltiae isolates, and identified up to three possible colonisation events of Bull Island. EPIC-PCR grouped two isolates, 33.D.(2) and 59.F.(2), separately from the remaining ten S. feltiae isolates These same two isolates consistently performed poorly in all fitness assessments. Following the crossbreeding of all isolates in Galleria mellonella, the number of host cadavers exhibiting emerging infective juveniles was significantly fewer than expected and there were significant differences between isolates in the number of days until progeny were observed. Host insect mortality varied between 40 and 87%. Such intraspecific variation may be a result of adaptation to different microhabitats of Bull Island, which in turn may be accentuated by laboratory culture practices.

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The integrated use of chemical insecticides and the entomopathogenic nematode, Steinernema feltiae, for the control of sweetpotato whitefly, Bemisia tabaci

Nematology ◽

10.1163/156854103322746887 ◽

2003 ◽

Vol 5 (5) ◽

pp. 713-720 ◽

Cited By ~ 26

Author(s):

Andrew Cuthbertson ◽

Justine Head ◽

Keith Walters ◽

Alistair Murray

Keyword(s):

Bemisia Tabaci ◽

Host Plants ◽

Galleria Mellonella ◽

Entomopathogenic Nematode ◽

Steinernema Feltiae ◽

Sweetpotato Whitefly ◽

Chemical Agents ◽

Direct Exposure ◽

Systemic Pesticide ◽

The Impact

AbstractThe integration of infective juveniles of the entomopathogenic nematode, Steinernema feltiae, with chemical insecticides to control second instar stages of the sweetpotato whitefly, Bemisia tabaci, was investigated. The effects of direct exposure for 24 h to field rate dilutions of four insecticides (imidacloprid, buprofezin, teflubenzuron and nicotine) on nematode infectivity to Galleria mellonella larvae were tested in a sand tube bioassay. Teflubenzuron had the least adverse effect on the nematodes whilst imidacloprid, buprofezin and nicotine significantly reduced nematode infectivity. The impact of dry insecticide residue present on tomato and verbena foliage on nematode infectivity against B. tabaci larvae was investigated for buprofezin, teflubenzuron and nicotine (imidacloprid is a systemic pesticide and no residues would occur on foliage). No significant reduction on the level of control of B. tabaci was recorded when compared with the infectivity of nematodes applied to residue-free foliage of either tomato or verbena plants. Nematodes in combination with imidacloprid gave significantly higher B. tabaci larvae mortality compared to either treatment individually on both host plants. The integration of S. feltiae and these chemical agents into an integrated pest management programme for the control of B. tabaci is discussed.

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Mechanisms of specificity of association between the nematode Steinernema scapterisci and its symbiotic bacterium

Parasitology ◽

10.1017/s0031182096008669 ◽

1997 ◽

Vol 114 (5) ◽

pp. 483-488 ◽

Cited By ~ 17

Author(s):

P. S. GREWAL ◽

M. MATSUURA ◽

V. CONVERSE

Keyword(s):

Galleria Mellonella ◽

Entomopathogenic Nematode ◽

Symbiotic Bacterium ◽

Bacterial Symbiont ◽

Steinernema Carpocapsae ◽

Infective Juvenile ◽

Symbiotic Bacteria ◽

Bacterial Symbionts ◽

First Report ◽

Successful Isolation

We suggest a new mechanism for the maintenance of specificity of the association between the entomopathogenic nematode Steinernema scapterisci and its symbiotic bacteria. We evaluated the development and reproduction of infective and non-infective juvenile S. scapterisci in monoxenic combinations with its symbiotic bacteria, Xenorhabdus sp. ‘S’ and with the bacterial symbiont of Steinernema carpocapsae and Steinernema riobravis. Although development of non-infective stages occurred on all Xenorhabdus spp., the development of infective juveniles to the 4th stage (‘dauer’ recovery) was significantly delayed and reduced with X. nematophilus and Xenorhabdus sp. ‘R’, the bacterial symbionts of S. carpocapsae and S. riobravis, respectively. ‘Dauer’ recovery improved significantly when the cultures of X. nematophilus and Xenorhabdus sp. ‘R’ were supplemented with cell-free filtrates from Xenorhabdus sp. ‘S’. The infective juvenile S. scapterisci produced in all 3 cultures were virulent to Galleria mellonella larvae, confirming successful retention of Xenorhabdus from other steinernematids in their intestine. In fact, S. scapterisci infective juveniles containing X. nematophilus or Xenorhabdus sp. ‘R’ were more virulent to G. mellonella than those containing their natural symbiont, Xenorhabdus sp. ‘S’. We believe that this is the first demonstration of the symbiont-specific exit of infective juveniles from the ‘dauer’ phase which represents the finest level of specificity of bacteria–nematode association. This is also the first report of successful isolation of the natural symbiont of S. scapterisci.

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The influence of organic matter content and media compaction on the dispersal of entomopathogenic nematodes with different foraging strategies

Parasitology ◽

10.1017/s0031182017001317 ◽

2017 ◽

Vol 144 (14) ◽

pp. 1956-1963 ◽

Cited By ~ 4

Author(s):

APOSTOLOS KAPRANAS ◽

ABIGAIL M. D. MAHER ◽

CHRISTINE T. GRIFFIN

Keyword(s):

Organic Matter ◽

Entomopathogenic Nematode ◽

Organic Matter Content ◽

Matter Content ◽

Steinernema Feltiae ◽

Foraging Strategies ◽

Infective Juvenile ◽

Soil Parameters ◽

Biological Pest Control ◽

Species Specific

SUMMARYIn laboratory experiments, we investigated how media with varying ratio of peat:sand and two levels of compaction influence dispersal success of entomopathogenic nematode (EPN) species with different foraging strategies: Steinernema carpocapsae (ambusher), Heterorhabditis downesi (cruiser) and Steinernema feltiae (intermediate). Success was measured by the numbers of nematodes moving through a 4 cm column and invading a wax moth larva. We found that both compaction and increasing peat content generally decreased EPN infective juvenile (IJ) success for all three species. Of the three species, H. downesi was the least affected by peat content, and S. carpocapsae was the most adversely influenced by compaction. In addition, sex ratios of the invading IJs of the two Steinernema species were differentially influenced by peat content, and in the case of S. feltiae, sex ratio was also affected by compaction. This indicates that dispersal of male and female IJs is differentially affected by soil parameters and that this differentiation is species-specific. In conclusion, our study shows that organic matter: sand ratio and soil compaction have a marked influence on EPN foraging behaviour with implications for harnessing them as biological pest control agents.

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First report of the entomopathogenic nematode, Steinernema carpocapsae, from Moghan region of Iran and its efficacy against the turnip moth, Agrotis segetum Denis and Schiffermuller (Lepidoptera: Noctuidae), larvae

Egyptian Journal of Biological Pest Control ◽

10.1186/s41938-019-0168-y ◽

2019 ◽

Vol 29 (1) ◽

Author(s):

Laleh Ebrahimi ◽

Zahra TanhaMaafi ◽

Parviz Sharifi

Keyword(s):

Entomopathogenic Nematode ◽

Lethal Effect ◽

Molecular Data ◽

Steinernema Carpocapsae ◽

Steinernema Feltiae ◽

Agrotis Segetum ◽

Likelihood Method ◽

Bootstrap Analysis ◽

Turnip Moth ◽

Lepidoptera Noctuidae

Abstract During a survey of entomopathogenic nematodes (EPNs) in Moghan region of Iran in 2015, a steinernematid species was isolated, using the Galleria-baiting method. Based on its morphological and phylogenetic analysis of molecular data, the isolate was identified as Steinernema carpocapsae. The ITS rDNA sequence was deposited in NCBI (National Center for Biotechnology Information) with accession number of MF187616.1. Nucleotide row data was edited, using MEGA 6.0 software, and homologous sequences were involved in analysis, using Blast software. Sequences were aligned using Clustal W. Bootstrap analysis. The phylogenetic tree was constructed by the maximum likelihood method, using MEGA 6.0 software, and Steinernema feltiae was used as out-group. The turnip moth, Agrotis segetum Denis and Schiffermuller (Lepidoptera: Noctuidae), is one of the most important and destructive cutworm pests in Moghan. Therefore, the lethal effect of S. carpocapsae isolate Moghan (IRMoghan) was evaluated in a soil assay against the last instar larvae of A. segetum under laboratory conditions. The bioassay results showed high susceptibility of the larvae to S. carpocapsae. The LC10, LC50, and LC90 values were 9.9, 54.13, and 246.2 IJs (infective juveniles) per larva of the pest, respectively (χ2 = 7.36; df = 3, P value = 0.061). Reproduction of the EPNs within the dissected cadavers was observed. The bioassay results indicated that the new isolate is a promising biocontrol agent against A. segetum larvae with success recycling through them.

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VIRULENCE OF ENTOMOPATHOGENIC NEMATODE–BACTERIA COMPLEXES FOR LARVAE OF NOCTUIDS, A GEOMETRID, AND A PYRALID

The Canadian Entomologist ◽

10.4039/ent122309-3 ◽

1990 ◽

Vol 122 (2) ◽

pp. 309-319 ◽

Cited By ~ 25

Author(s):

O.N. Morris ◽

V. Converse ◽

J. Harding

Keyword(s):

Galleria Mellonella ◽

Entomopathogenic Nematode ◽

Heterorhabditis Bacteriophora ◽

Steinernema Feltiae ◽

Agrotis Ipsilon ◽

Pseudaletia Unipuncta ◽

Mamestra Configurata ◽

Euxoa Ochrogaster ◽

Cold Hardy ◽

Highly Virulent

AbstractNine entomopathogenic nematode–bacteria complexes were screened for their virulence against larvae of six noctuids, a geometrid, and a pyralid. Ninety-six-hour LD50’s of steinernematids (and heterorhabditids) ranged from 1 to 3 (1–8) infective juveniles in Galleria mellonella (L.), 1–71 (2) in Peridroma soucia (Hbn.), 1–10 (1–3) in Mamestra configurata (Wlk.), 1–28 (3–7) in Euxoa ochrogaster (Gn.), 19 in Lacanobia radix (Wlk.), 22–60 (4) in Pseudaletia unipuncta (Haw.), 2–95 (111) in Agrotis ipsilon (Hufn.), and 3–28 in Paleacrita vernata (Peck). The nematode, Steinernema feltiae LIC, a cold-hardy strain isolated in Newfoundland, was highly virulent for G. mellonella and M. configurata, but not for P. soucia and E. ochrogaster. The number of nematodes invading larvae and the number produced were greater in G. mellonella than in other insects tested. Nematode–bacteria complexes that showed potential for controlling cutworms included S. feltiae, S. glaseri, S. bibionis, Heterorhabditis bacteriophora, and H. heliothidis.

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MORPHOLOGICAL AND BIOLOGICAL VARIABILITY OF STEINERNEMA FELTIAE (NEMATODA, STEINERNEMATIDAE) ITALIAN STRAINS

Redia ◽

10.19263/redia-103.20.24 ◽

2020 ◽

Vol 103 ◽

pp. 153-160

Author(s):

MIRELLA CLAUSI ◽

ALBERTO TROCCOLI ◽

FRANCESCA DE LUCA ◽

GIANCARLO RAPPAZZO ◽

ELENA FANELLI ◽

...

Keyword(s):

Entomopathogenic Nematode ◽

Intraspecific Variability ◽

Single Species ◽

Diagnostic Value ◽

Biological Properties ◽

Biological Data ◽

Molecular Techniques ◽

Steinernema Feltiae ◽

Biological Traits ◽

Different Strains

Steinernema feltiae belongs to the feltiae-kraussei-oregonensis group, clade III, and is an ubiquitarian species of entomopathogenic nematode. It is found in all types of soil and in all types of habitat. Species identification in the entomopathogenic nematodes genera Steinernema is a very complex task, given the broad variability of both morphological and biological traits within populations of a single species. To accomplish this, molecular techniques have been adopted which, however, require additional knowledge. Particularly relevant would be the possibility of testing in a reliable way the variability between different populations of the same species, which might represent different strains with different biological properties. During numerous samplings in Italy, several strains of S. feltiae were isolated. In this paper we analyze the intraspecific variability of the main morphometric and biological data of juveniles and males of 50 Italian populations of S. feltiae. The aim of our work was to determine if morphometric and biological analysis were useful to identify characters having significant diagnostic value, allowing to reliably discriminate among strains. Seven characters routinely computed for morphology (5 morphometrics for infective juveniles, spicula and gubernaculum shapes for males) and 2 biological performances (time to achieve adult stage, reproduction and progeny) were considered. The results showed extreme variability from both morphological and biological points of view

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