Entomopathogenic Nematode Heterorhabditis Bacteriophora Research Articles

Forecasting Western Corn Rootworm (Diabrotica virgifera virgifera LeConte) Density and Non-Chemical Control of Larvae: A Practical Review

The western corn rootworm (WCR) (Diabrotica virgifera virgifera LeConte; Chrysomelidae) is one of the most significant maize pests in Europe, with farmers spending a substantial amount (approximately 140 EUR) on its control. In the context of climate change, WCRs could pose an even greater threat to EU maize production, particularly as the European Union continues to withdraw an increasing number of effective yet environmentally harmful active agents. Biological control methods have now emerged to the forefront in creating sustainable agriculture. In this review, we carried out an extensive literature analysis on methods for forecasting WCRs and evaluated the practical applicability of the latest non-chemical control methods targeting its larvae. Effective forecasting is essential for successful pest management, enabling informed planning and the selection of the most suitable control methods. Several traditional predicting techniques remain in use today, but recent advancements have introduced modern electronic forecasting units combined with sensor-equipped pheromone and colour traps, as well as thermal sum calculations. Research has demonstrated that crop rotation is one of the most effective methods for controlling WCR larvae. Biological agents, such as entomopathogenic fungi (Beauveria bossiana and Mettarrhyzum anasoplia), entomopathogenic nematodes (Heterorhabditis bacteriophora), and botanical insecticides such as azadirachtin can significantly reduce larval populations and root damage, thereby maintaining infestation levels below the economic threshold. Genetically modified maize plants that produce specific toxins, along with conventional breeding efforts to increase root system regeneration, are also promising tools for the sustainable management of this pest. This review summarizes the solutions for prediction of western corn rootworm infestations and non-chemical control of its larvae. Accurate forecasting methods provide a clear picture of infestation levels in a given area, enabling precisely targeted control measures. In all cases, the control should be directed primarily against the larvae, thereby reducing root damage and reducing the size of the emerging imago population. This review demonstrates that biological control methods targeting larvae can be as effective as pesticides, supporting sustainable pest management.

Sodium Hypochlorite: Optimization of Application as an Exsheathing Agent for Nematode Larvae to Minimize the Risk of Reduced Viability

Objective: Nematode larvae exsheathing is a crucial procedure employed in experimental studies such as nematode viability assays, evaluating nematodes' resistance to anthelmintics, and evaluating the efficacy of anthelmintic medications. The exsheathment procedure allows for quantifying the direct impact on larvae when the protective sheath is removed. Sodium hypochlorite (NaOCl) is a commonly used artificial exsheathment medium. However, concerns have been raised about its potential impact on the viability of exsheathed larvae. A previous study utilized Strongyloides papillosus larvae, a nematode species without a protective sheath, to investigate the effects of NaOCl on parasite viability. The findings revealed that there are specific concentration (C) and exposure-time (T) thresholds (0.3% > C > 0.2%; 10 min > T > 5 min) beyond which viability decreases, and excessive exposure can cause significant damage. The current study aims to determine the optimal concentration of NaOCl that can induce exsheathment in ensheathed-type larvae without compromising their viability. Methods: Third-stage strongylid larvae of donkey origin were utilized for this study, with chemical concentrations of 3%, 0.3%, 0.2%, 0.1%, or 0.05%. Larval motility served as the criterion for evaluating viability. Results: NaOCl can exsheath larvae at any of the five concentration levels evaluated, depending on the duration of exposure to the compound. A concentration of 0.2% is considered optimal, inducing exsheathment as early as 2 minutes. Extended exposure for up to 10 minutes did not impact larval viability. A 3% solution causes larval damage. Conclusions: Regarding the effect of NaOCl on nematode larvae, the results validate the earlier findings with Strongyloides papillosus and those by other authors employing nematodes such as Haemonchus contortus and Cooperia curticei, and the entomopathogenic nematode Heterorhabditis bacteriophora.

Dauer juvenile recovery transcriptome of two contrasting EMS mutants of the entomopathogenic nematode Heterorhabditis bacteriophora.

The entomopathogenic nematode Heterorhabditis bacteriophora, symbiotically associated with enterobacteria of the genus Photorhabdus, is a biological control agent against many insect pests. Dauer Juveniles (DJ) of this nematode are produced in industrial-scale bioreactors up to 100 m3 in liquid culture processes lasting approximately 11days. A high DJ yield (> 200,000 DJ·mL-1) determines the success of the process. To start the mass production, a DJ inoculum proceeding from a previous monoxenic culture is added to pre-cultured (24h) Photorhabdus bacteria. Within minutes after contact with the bacteria, DJ are expected to perceive signals that trigger their further development (DJ recovery) to reproductive hermaphrodites. A rapid, synchronized, and high DJ recovery is a key factor for an efficient culture process. In case of low percentage of DJ recovery, the final DJ yield is drastically reduced, and the amount of non-desired stages (males and non-fertilized females) hinders the DJ harvest. In a preliminary work, a huge DJ recovery phenotypic variability in H. bacteriophora ethyl methanesulphonate (EMS) mutants was determined. In the present study, two EMS-mutant lines (M31 and M88) with high and low recovery phenotypes were analyzed concerning their differences in gene expression during the first hours of contact with Photorhabdus supernatant containing food signals triggering recovery. A snapshot (RNA-seq analysis) of their transcriptome was captured at 0.5, 1, 3 and 6h after exposure. Transcripts (3060) with significant regulation changes were identified in the two lines. To analyze the RNA-seq data over time, we (1) divided the expression profiles into clusters of similar regulation, (2) identified over and under-represented gene ontology categories for each cluster, (3) identified Caenorhabditis elegans homologous genes with recovery-related function, and (4) combined the information with available single nucleotide polymorphism (SNP) data. We observed that the expression dynamics of the contrasting mutants (M31 and M88) differ the most within the first 3h after Photorhabdus supernatant exposure, and during this time, genes related to changes in the DJ cuticle and molting are more active in the high-recovery line (M31). Comparing the gene expression of DJ exposed to the insect food signal in the haemolymph, genes related to host immunosuppressive factors were not found in DJ upon bacterial supernatant exposure. No link between the position of SNPs associated with high recovery and changes in gene expression was determined for genes with high differential expression. Concerning specific transcripts, nine H. bacteriophora gene models with differential expression are provided as candidate genes for further studies.

Dos inseticidas ao controle biológico de pragas na cana-de-açúcar: uma experiência de meio século na Venezuela

Biological control has been established as a unique measure for managing borers of the genus Diatraea and the candelilla Aeneolamia spp., both of which are key pests of sugarcane in Venezuela. Optimal results have been achieved with the use of parasitoids and entomopathogens. Systematic releases of the Amazonian fly Lydella minense from the mid-20th century and the establishment of the braconid wasp Cotesia flavipes from 1987 led to effective control of borers. In the case of Aeneolamia varia, a pest formerly controlled with frequent insecticide applications, an efficient solution was the introduction of the entomopathogenic fungus Metarhizium anisopliae in 1977. This measure has been established as efficient in controlling adult Aeneolamia, though nymphs were less controlled. This issue was effectively addressed in 2004 with the introduction of the entomopathogenic nematode Heterorhabditis bacteriophora, which has been widely used as a biological measure to avoid the application of insecticides. To illustrate this, we can consider the case of Azucarera Río Turbio. Despite experiencing a reduction in cultivated areas in recent harvests due to various factors, this establishment has witnessed a significant decline in Diatraea infestations over the past 58 years. Infestation rates have decreased from 15% to 3.18%, resulting in a saving of 170,552.62 metric tons valued at USD 49,196,045. The cost of implementing biological control measures amounts to USD 1,187,189, translating into a favorable benefit-cost ratio of USD 41.44. Before the adoption of biological control methods, Aeneolamia infestations were exclusively controlled using chemical insecticides applied to both the foliage for adults and the soil for nymphs. Concurrently, since then, entomopathogenic fungus M. anisopliae, produced by national companies, has been deployed across 87,000 hectares between 1986 and 1990. Moreover, since 2004, the use of entomopathogenic nematodes to control Aeneolamia nymphs has been integrated into pest management practices.

Monitoring the Photorhabdus spp. bacterial load in Heterorhabditis bacteriophora dauer juveniles over different storage times and temperatures: A molecular approach

Biological control products based on the entomopathogenic nematode Heterorhabditis bacteriophora can vary in virulence (quality). The influence of their symbiotic bacteria Photorhabdus spp. inside the infective dauer juvenile (DJ) on DJ quality has not received much attention in the past. The presence of the bacteria in the DJ is crucial for its biocontrol potential. This investigation provides a method to quantify the bacterial load inside the DJ based on a qPCR technique. Information from the genome of Photorhabdus laumondii strain DE2 was used to identify single copy genes with no homology to any other bacterial accessions. One gene (hereby named CG2) was selected for primers design and for further qPCR experiments. Cross-amplification tests with P. thracensis and P. kayaii, also symbionts of H. bacteriophora, were positive, whereas no amplicons were produced for P. temperata or Xenorhabdus nematophila. We tested our qPCR system in DJ populations carrying defined proportions of bacteria-free (axenic) vs bacteria-carrying nematodes. With an increasing proportion of axenic DJ in a population, virulence declined, and the virulence was proportional to the amount of bacterial DNA detected in the population by qPCR. Along liquid storage over long time, virulence also decreased, and this factor correlated with the reduction of bacterial DNA on the respective DJ population. We observed that stored DJ kept virulent up to 90 days and thereafter the virulence as well as the amount of bacterial DNA drastically decreased. Storage temperature also influenced the bacterial survival. Inside formulated DJ, the loss of bacterial DNA on the DJ population was accelerated under storage temperatures below 7.5 °C, suggesting that reproduction of the bacterial cells takes place when growth temperature is favorable. The role of bacterial survival inside stored DJ can now be adequately addressed using this molecular quality-control technique.

Genotypic markers associated with cold storage survival of the entomopathogenic nematode Heterorhabditis bacteriophora

Summary Limited shelf life is a major constraint to successful commercialisation of entomopathogenic nematodes (EPN), and to extend shelf life, dauer juveniles (DJ) are formulated and stored at low temperatures (4-8°C). We evaluated the cold storage potential of strains of Heterorhabditis bacteriophora formulated in diatomaceous earth at storage temperatures between 5 and 9°C. When assessing DJ decline to reach 75% survival (MT75) in the formulation for the respective temperatures, H. bacteriophora strain HB4 had the highest survival of 25 days at 9°C, while strain D2D6 survived longest at 8°C for 28 days. A set of 22 H. bacteriophora wild type inbred lines was then phenotyped for cold tolerance in water under oxidative stress in 70 mM H2O2 at 2°C. The MT50 (time to 50% survival) ranged from 11 to 23 days. The phenotypic data were correlated with the respective genotypic data, identifying four single nucleotide polymorphic (SNP) markers associated with cold tolerance. The survival of two lines (PT11 and IR11) with opposite extreme cold tolerance pheno- and genotypes was evaluated in diatomaceous earth formulation at 2°C with the cold tolerant IR11 surviving 3 days longer than PT11. Our study yields a set of valuable SNP markers employable in rapid genotyping of cold tolerance and tracking this trait during the breeding process.

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.

Alterations in the metabolism of Pseudosuccinea columella (Mollusca: Gastropoda) caused by Heterorhabditis bacteriophora HP88 (Rhabditida: Heterorhabditidae)

The gastropod Pseudosuccinea columella participates in the dissemination of Fasciola hepatica in the environment, acting as the main intermediate host of this parasite in Brazil. The present study sought to elucidate the possible pathogenic effects of the entomopathogenic nematode (EPN) Heterorhabditis bacteriophora on P. columella, by evaluating the influence of infection on alanine aminotransferase (ALT) and aspartate aminotransferase (AST), as well as the concentrations of total protein, uric acid, and urea in the snail's hemolymph. For this, the snails were exposed to EPNs for 24 and 48 h, and for each exposure time, 20 snails were dissected after 7, 14 and 21 days for hemolymph collection. The primary findings suggest a significant proteolysis alongside elevated levels of uric acid and urea in P. columella infected individuals. These findings reveal that H. bacteriophora HP88 infection induced serious changes in the snail's metabolism, triggering important deleterious effects.

Efficiency of temperature and storage duration on some morphological measurements and reproductive capacity of the entomopathogenic nematode Heterorhabditis bacteriophora Poinar, 1976 (Rhabditida: Heterorhabditidae)’s Turkish HBH hybrid strain

Entomopathogenic nematodes (EPNs) are successfully used in the biological control of agricultural insect pests. This study aims to determine the body length of hermaphrodite individuals, egg diameter and reproductive capacity obtained from Infective Juveniles (IJs) stored at different temperatures and durations. Heterorhabditis bacteriophora Poinar, 1976 (Rhabditida: Heterorhabditidae)’s Hybrid Strain HBH was used in the study. IJs stored at 15, 25 and 35°C for 7, 14 and 21 days were inoculated onto Galleria mellonella L., 1758 (Lepidoptera: Pyralidae) last instar larvae at a dose of 100 IJs. On the 2nd day of infection, hermaphrodite individuals and eggs were obtained by dissecting the larvae. The reproductive capacity was determined 10-12 days after infection. The study was conducted in Bursa Uludağ University, Faculty of Agriculture, Plant Protection Department, Nematology Laboratory in 2023. In conclusion, the longest hermaphrodite individuals and egg diameter were obtained as 6207.22 µm and 55.65 µm, respectively from the IJs stored for 7 days at 15°C. The highest reproductive capacity was also observed as 167.500 IJs per G. mellonella larva in IJs stored under the same conditions with respect to temperature and time. This study is important for assessing the morphological effects of different temperature values and storage durations on EPNs.

Pheno- and genotyping in vitro dauer juvenile recovery in the nematode Heterorhabditis bacteriophora.

The entomopathogenic nematode (EPN) Heterorhabditis bacteriophora is an effective biological-control agent of insect pests. The dauer juveniles (DJs) seek for, infect insects, and release cells of the carried symbiotic bacterium of the genus Photorhabdus. Inside the host, the DJs perceive signals from the insect's haemolymph that trigger the exit from the arrested stage and the further development to mature adults. This developmental step is called DJ recovery. In commercial production, a high and synchronous DJ recovery determines the success of liquid-culture mass production. To enhance the understanding about genetic components regulating DJ recovery, more than 160 mutant- and 25 wild type inbred lines (WT ILs) were characterized for DJ recovery induced by cell-free bacterial supernatant. The mutant lines exhibited a broader DJ recovery range than WT ILs (4.6-67.2% vs 1.6-35.7%). A subset of mutant lines presented high variability of virulence against mealworm (Tenebrio molitor) (from 22 to 78% mortality) and mean time survival under oxidative stress (70 mM H2O2; from 10 to 151 h). Genotyping by sequencing of 96 mutant lines resulted in more than 150 single nucleotide polymorphisms (SNPs), of which four results are strongly associated with the DJ recovery trait. The present results are the basis for future approaches in improving DJ recovery by breeding under in vitro liquid-culture mass production in H. bacteriophora. This generated platform of EMS-mutants is as well a versatile tool for the investigation of many further traits of interest in EPNs. KEYPOINTS: • Exposure to bacterial supernatants of Photorhabdus laumondii induces the recovery of Heterorhabditis bacteriophora dauer juveniles (DJs). Both, the bacteria and the nematode partner, influence this response. However, the complete identity of its regulators is not known. • We dissected the genetic component of DJ recovery regulation in H. bacteriophora nematodes by generating a large array of EMS mutant lines and characterizing their recovery pheno- and genotypes. • We determined sets of mutants with contrasting DJ recovery and genotyped a subset of the EMS-mutant lines via genotyping by sequencing (GBS) and identified SNPs with significant correlation to the recovery trait.

Precision application of the entomopathogenic nematode Heterorhabditis bacteriophora as a biological control agent through the Nemabot

One of the most important development trends of robots in agriculture is to enable highly precise applications that minimize amounts of chemical components that are harmful to the environment. Precision agriculture is fundamental and inevitable worldwide because it provides more yield to an increasing population, while at the same time reducing inputs. The purpose of this study was to apply entomopathogenic nematodes, which are insect parasites used as biological control agents, through Nemabot. A robotic system that can move in the X-Y-Z coordinate plane has an agitating mechanism for suspension based on water and entomopathogenic nematodes and can perform precise dosing with a peristaltic pump designed and produced as a prototype. The experimental results of the robot application on the exact point, volume, amount, and uniformity of dosing show that the proposed method can effectively solve the problem of applying entomopathogenic nematodes, which are economically more expensive than pesticides. The main contribution of this paper is the proposal of a method to solve the problem of applying the agents precisely. This is the first experiment in which biological control products were applied using a robotic system. A patent application (PCT/TR2019/050768) was made, and the patentability claims were approved and officially registered (TR2018 14310B).

Efficacy of entomopathogenic fungi, nematodes and spinetoram combinations for integrated management of Thrips tabaci.

Two consecutive field trials using a blend of entomopathogens in combination with a new chemistry insecticide were conducted to determine treatment effects on onion thrips (Thrips tabaci Lindeman) populations, crop damage, plant development, crop yield and impact on natural enemies. Products were tested in an onion cropping system and included the insect pathogenic fungus Beauveria bassiana (isolate WG-11), an entomopathogenic nematode Heterorhabditis bacteriophora (strain VS) and the new-chemistry chemical insecticide spinetoram. In all treatments, a significant decrease in thrips per plant population was detected in both trials. Overall, dual application of entomopathogens and insecticide was more effective than singly applied treatments. The lowest number of thrips larvae (1.96 and 3.85) and adults (0.00 and 0.00) were recorded when treated with dual application of B. bassiana and spinetoram at 7 days post application (DPA) after the second spray application in 2017and 2018, respectively. Damage on onion plants was considerably decreased in all treatments relative to the control. The lowest damage was observed on onion plants treated with B. bassiana + spinetoram at 7 DPA after the second spray application during both years. A significant decrease in the number of natural enemies (beetles, spiders, mites, lacewings, ants and bugs) on onion plants was recorded during both years. Insect pathogens when applied alone and in combination with each other considerably protected arthropod natural enemies compared to insecticide application applied alone. Significant increase in plant agronomic traits was observed compared to the control. Among all the treatments, B. bassiana + spinetoram produced maximum leaf length, leaf weight, total leaves, neck diameter, bulb diameter, number of rings per bulb, bulb weight, dry matter and plant yield following the 2017and 2018 applications, respectively. The findings of the study reveal the potential of using insect pathogens and insecticide for control of T. tabaci. However, combinations containing spinetoram are harmful to nontarget organisms, whereas biological control agents help in protecting biodiversity in onion agroecosystems. © 2023 Society of Chemical Industry.

Efficacy of a native entomopathogenic nematode Heterorhabditis bacteriophora (isolate Z-1) against potato tuber moth (Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae) in Turkey

BackgroundPotato tuber worm (PTM) [Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae)] is one of the most significant and widespread pests of potato. PTM damages potatoes both in the field and in potato storage areas. Control of the pest is getting harder as it is developing resistance to pesticides. Several entomopathogenic nematode (EPN) species have been reported to successfully control numerous agricultural pests worldwide. The main aim of the study was to isolate native nematode/s as a biological control agent against P. operculella. Morphometric measurements of the infective juvenile (IJ) and sequencing and characterization of the internal transcribed spacer (ITS) region was used to identify the nematode isolate to species level. The efficacy of EPN isolate Z-1 obtained from Zonguldak province, Turkey was tested against different life stages of the pest. Experiments were conducted in 150 ml plastic pots containing sterile soil mixture. Four EPN concentrations (i.e., 0, 250, 500 and 1000 IJs/ml) were applied to the soil. Data relating to the mortality of different life stages were collected daily till 6 days after inoculation.ResultsMolecular analyses based on the ITS sequence and morphometric data revealed that isolate Z-1 was Heterorhabditis bacteriophora. Mortality rates of PTM larvae exposed to 250, 500, and 1000 IJs/ml concentrations of native EPN were 62.9 ± 9.8, 74.0 ± 3.7, and 92.5 ± 3.7%, respectively. There were non-significant differences among tested EPN concentrations for pupal mortality and the highest concentration (i.e., 1000 IJs/ml) caused 25.6% mortality.ConclusionsThe results revealed that the native H. bacteriophora isolate was effective against late-stage larvae of PTM under laboratory conditions. Therefore, it can be used as an alternative management option of the pest.

Effect of entomopathogenic nematodes Steinernema species (steinernematidae: rhabditida) and Heterorhabditis bacteriophora (heterorhabditidae: rhabditida) on the digestive enzymes and midgut histology of the African migratory locust Locusta migratoria migratorioides (acrididae: orthoptera)

In some governorates of Egypt, the African migratory locust L. migratoria migratorioides is in a gregarious phase. Swarm development was successfully prevented by biological control agents. In this work, the two entomopathogenic nematode species, Steinernema sp. (SII)and Heterorhabditis bacteriophora (HP88) were investigated as natural enemies against the fifth nymph and adult African locusts at various concentrations (300, 600, 900, 1200, and 1500 Infected juveniles/100 g. soil). To ascertain fatal activity at 25 °C, the nematode-inoculated sand method was used. The two nematode species were semi-field administered against fifth nymphs and adult stages at (25 ± 2 °C) and 55–60% relative humidity with concentrations (3000, 6000, 9000, 12000, and 15000 Infected juveniles/kg. soil). Protease, amylase, invertase, and trehalase levels in the digestive enzymes of both fifth nymphs and adults fed with LC50 of both nematodes significantly decreased, but lipase and chitinase levels significantly increased. Adult locusts treated with the LC50 of S. sp. SII had basophilic epithelial cells, severe lumen hemorrhage, and highly aberrant proliferating cytoplasm, whereas the LC50 of H. bacteriophora HP88 displayed necrosis in an epithelial cell with vacuoles, loss of nucleus, and loss of goblet cells.

HETERORHABDITIS BACTERIOPHORA NEMATODES ARE SENSITIVE TO THE BACTERIAL PATHOGEN PHOTORHABDUS ASYMBIOTICA.

The entomopathogenic nematode (EPN) Heterorhabditis bacteriophora infects a wide range of insect hosts with the aid of its mutualistic bacteria Photorhabdus luminescens. While the mutualistic relationship between H. bacteriophora and P. luminescens and the infectivity of the nematode-bacteria complex have been characterized, how nematode fitness is affected by entomopathogenic bacteria existing in association with other EPN species remains poorly understood. In this study, the survival of H. bacteriophora infective juveniles containing or lacking P. luminescens was tested against the entomopathogenic bacteria Xenorhabdus nematophila and Photorhabdus asymbiotica as well as the non-pathogenic Escherichia coli. While X. nematophila and E. coli did not significantly affect the survival of H. bacteriophora, P. asymbiotica exerted a significant effect on nematode survival, particularly on those lacking P. luminescens. These results imply that P. asymbiotica encodes factors that are pathogenic to EPNs. Future efforts will focus on the identification of the bacterial molecular components that induce these effects. This study makes an important contribution to a growing body of research aimed at exploiting the full potential of nematode-bacterial complexes for eliminating noxious insect pests and treating infectious diseases caused by parasitic nematodes.

Stringent in-silico identification of putative G-protein-coupled receptors (GPCRs) of the entomopathogenic nematode Heterorhabditis bacteriophora.

The infective juveniles (IJs) of entomopathogenic nematode (EPN) Heterorhabditis bacteriophora find and infect their host insects in heterogeneous soil ecosystems by sensing a universal host cue (CO2) or insect/plant-derived odorants, which bind to various sensory receptors, including G protein-coupled receptors (GPCRs). Nematode chemosensory GPCRs (NemChRs) bind to a diverse set of ligands, including odor molecules. However, there is a lack of information on the NemChRs in EPNs. Here we identified 21 GPCRs in the H. bacteriophora genome sequence in a triphasic manner, combining various transmembrane detectors and GPCR predictors based on different algorithms, and considering inherent properties of GPCRs. The pipeline was validated by reciprocal BLAST, InterProscan, GPCR-CA, and NCBI CDD search. Functional classification of predicted GPCRs using Pfam revealed the presence of four NemChRs. Additionally, GPCRs were classified into various families based on the reciprocal BLAST approach into a frizzled type, a secretin type, and 19 rhodopsin types of GPCRs. Gi/o is the most abundant kind of G-protein, having a coupling specificity to all the fetched GPCRs. As the 21 GPCRs identified are expected to play a crucial role in the host-seeking behavior, these might be targeted to develop novel insect-pest management strategies by tweaking EPN IJ behavior, or to design novel anthelminthic drugs. Our new and stringent GPCR detection pipeline may also be used to identify GPCRs from the genome sequence of other organisms.

Drosophila melanogaster larvae are tolerant to oral infection with the bacterial pathogen Photorhabdus luminescens.

The fruit fly Drosophila melanogaster is an excellent model for dissecting the molecular and functional bases of bacterial pathogenicity and host antibacterial immune response. The Gram-negative bacterium Photorhabdus luminescens is an insect-specific pathogen that forms a mutualistic relationship with the entomopathogenic nematode Heterorhabditis bacteriophora . Here we find that oral infection of D. melanogaster larvae with P. luminescens moderately reduces their survival ability while the bacteria replicate efficiently in the infected insects. This information will contribute towards understanding host gut immunity against potent bacterial pathogens.

Şeftali bahçesinde damla sulama yöntemi ile toprağa uygulanan yerel entomopatojen nematodların kalıcılığının belirlenmesi

The period of persistence of entomopathogenic nematodes (EPNs) in soil is an important factor in the success of biological control efforts. In this study, the persistency of four native Turkish entomopathogenic nematode species, Steinernema feltiae (Filipjev), S. carpocapsae (Weiser), S. affine (Bovien) and Heterorhabditis bacteriophora (Poinar), was investigated in a peach orchard after their application with a drip irrigation system in Çanakkale Province, Turkiye, in 2018 and 2019. The EPNs were applied at the rate of 50 IJs/cm2. After application, the persistency of the EPNs was determined with soil sampling on a monthly basis. EPN persistence in the soil was 90 days and 150 days in 2018 and 2019, respectively. Additionally, the persistency of the EPNs in soil after their application varied, depending on environmental factors. The longer survival of EPNs in soil after application is important for the increase of the efficiency of EPNs against pests. It was concluded that the local EPN species have potential for use in the biological control of agricultural pests.

Combined application of entomopathogenic nematodes and fungi against fruit flies, Bactrocera zonata and B. dorsalis (Diptera: Tephritidae): laboratory cups to field study.

The peach fruit fly, Bactrocera zonata, and the Oriental fruit fly, B.dorsalis (Diptera: Tephritidae), are economically important fruit fly species in various regions of the world. We evaluated the effects of separate and combined applications of the entomopathogenic fungi (EPF) Beauveria bassiana (WG-18) and Metarhizium anisopliae (WG-02), and the entomopathogenic nematodes (EPNs) Heterorhabditis bacteriophora (VS strain) and Steinernema carpocapsae (ALL strain) against larvae, pupae and pharate adults, of B.zonata and B.dorsalis under laboratory, glasshouse and field cage conditions. Combined applications of EPF and EPNs produced greater mortality than individual treatments under all conditions. Against both species, the combination of B. bassiana and H.bacteriophora consistently exerted strong effects that were similar to the combined application of B.bassiana and S.carpocapsae whereas M.anisopliae applied with S.carpocapsae was least effective in all combinations. In a laboratory bioassay, synergistic interactions were detected between B.bassiana and H.bacteriophora applied against larvae and pharate adults of both fly species, between B.bassiana and S.carpocapsae against larvae of both species and pharate adults of B.zonata, and between M.anisopliae and H.bacteriophora against B.zonata larvae. Other combined treatments resulted in additive effects, especially against fly pupae. In a potted soil bioassay, there were only additive interactions in all combinations against different stages of both flies. The 3rd instar of both flies was more susceptible than pharate adult and pupal stages. Additive interactions between EPNs and EPF were detected in the glasshouse against 3rd instars and pupae, and under field conditions against 3rd instars of both fly species. These results indicate how particular combinations of entomopathogenic fungi and nematodes could be deployed in integrated pest management of tephritid fruit flies in orchard agro-ecosystems. © 2022 Society of Chemical Industry.

Infectivity of entomopathogenic nematode against the cabbage butterfly (Pieris brassicae L.) in polyhouse and in field condition

BackgroundCabbage butterfly, Pieris brassicae Linnaeus (Lepidoptera: Pieridae), is a major insect pest affecting cole crops worldwide. Excessive applications of chemical-based insecticides have a devastating impression over the organisms and environment.ResultsIn this study, entomopathogenic nematode (EPN) Heterorhabditis bacteriophora Poinar strain EUPT-S26 (local isolate) was evaluated for Pieris brassicae control under polyhouse and field conditions. Under the polyhouse conditions, the highest insect mortality 91.6 and 94.0% was observed in the plots treated with the nematodes suspension 1500 IJs/ml and 2000 IJs/ml, respectively. Based on the highest cabbage plant protection under polyhouse conditions, H. bacteriophora EUPT-S26 was also applied for field assays in the course of the crop’s productive phase. Data demonstrated from the field treatments signify the highest concentration (2000 IJs/ml) showed the maximum larval mortality and least damage percentage 45 ± 1.07% that remained constant until harvesting; this resulted in the highest productivity in polyhouse and under field conditions.ConclusionAccording to assessed field conditions, it was suggested to perform 3 applications of EPNs during the vegetative phase and at the time of head formation to increase productivity and to reduce damage. The results approved that EPNs are an effective alternative of chemical-based insecticides to control the cabbage butterfly.