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      Morphological adjustment in free-living Steinernema feltiae infective juveniles to increasing concentration of Nemafric-BL phytonematicide

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      PLoS ONE

      Public Library of Science

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          Abstract

          Third-stage larvae (L3) of Steinernema feltiae exist as free-living infective juveniles (IJ), with suspended development activities. In contrast, parasitic stages (L1, L2, L4, adult) have mutualistic relations with Xenorhabdus species bacteria, along with unique morphological changes and development inside the cadaver of host insects and/or plant-parasitic nematodes. Commercial IJ strains are tolerant to cucurbitacin-containing phytonematicides, but we have scant information on how morphological adjustments in IJ are achieved. In this study, we investigated the nature of morphological adjustments in commercial S. feltiae IJ strains to Nemafric-BL phytonematicide, which contains cucurbitacin B as active ingredient. Post-72 h exposure to phytonematicide concentration, IJ specimens were fixed on mounting slides. Length (body, excretory pore to anterior end, pharynx, rectum, stoma, tail), diameter (head width, neck base, mid-body, anal body), cuticle thickness and De Man ratios were measured with a computer software programme attached to Omax light microscope. Morphometric data against increasing phytonematicide concentration exhibited either density-dependent quadratic, linear or neutral relations. Increase in body length at low phytonematicide concentration was accompanied by decrease in tail length and pharynx length during muscle contraction when IJ were still alive. After death at high phytonematicide concentration, the opposite morphometric effects ensued due to muscle relaxation. The observed changes in morphometric structures were explained on the basis of morphological adjustments that modulated volumes of pseudocoelom cavity in IJ. The modulation is intended to maintain hydrostatic pressure within permissible upper limits in order to avoid structural damage to internal organs embedded in the pseudocoelom fluids.

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          Most cited references 23

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          Entomopathogenic Nematodes

           H K Kaya,  R Gaugler (1993)
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            Behavioral ecology of entomopathogenic nematodes

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              Entomopathogenic nematodes for control of insect pests above and below ground with comments on commercial production.

              Entomopathogenic nematodes (EPNs) have been utilized in classical, conservation, and augmentative biological control programs. The vast majority of applied research has focused on their potential as inundatively applied augmentative biological control agents. Extensive research over the past three decades has demonstrated both their successes and failures for control of insect pests of crops, ornamental plants, trees and lawn and turf. In this paper we present highlights of their development for control of insect pests above and below ground. The target insects include those from foliar, soil surface, cryptic and subterranean habitats. Advances in mass-production and formulation technology of EPNs, the discovery of numerous efficacious isolates/strains, and the desirability of reducing pesticide usage have resulted in a surge of commercial use and development of EPNs. Commercially produced EPNs are currently in use for control of scarab larvae in lawns and turf, fungus gnats in mushroom production, invasive mole crickets in lawn and turf, black vine weevil in nursery plants, and Diaprepes root weevil in citrus in addition to other pest insects. However, demonstrated successful control of several other insects, often has not lead to capture of a significant share of the pesticide market for these pests.
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                Author and article information

                Contributors
                Role: ConceptualizationRole: MethodologyRole: Writing – original draftRole: Writing – review & editing
                Role: MethodologyRole: Software
                Role: MethodologyRole: Software
                Role: Editor
                Journal
                PLoS One
                PLoS ONE
                plos
                plosone
                PLoS ONE
                Public Library of Science (San Francisco, CA USA )
                1932-6203
                3 January 2020
                2020
                : 15
                : 1
                Affiliations
                [1 ] University of Limpopo, Green Biotechnologies Research Centre of Excellence, Sovenga, Republic of South Africa
                [2 ] Agricultural Research Council-VOP, Pretoria, Republic of South Africa
                University of California Riverside, UNITED STATES
                Author notes

                Competing Interests: The authors have declared that no competing interests exist.

                Article
                PONE-D-19-15401
                10.1371/journal.pone.0227448
                6941822
                31899763
                © 2020 Mashela et al

                This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

                Page count
                Figures: 6, Tables: 1, Pages: 14
                Product
                Funding
                This work was supported by the Flemish Interuniversity Council, the Agricultural Research Council (ARC) through the ARC–Universities Collaboration Centres, the National Research Foundation of South Africa through the Smallholder Development grant from the Department of Agriculture, Forestry and Fisheries.
                Categories
                Research Article
                Research and Analysis Methods
                Imaging Techniques
                Morphometry
                Biology and Life Sciences
                Physiology
                Muscle Physiology
                Muscle Contraction
                Medicine and Health Sciences
                Physiology
                Muscle Physiology
                Muscle Contraction
                Physical Sciences
                Physics
                Classical Mechanics
                Pressure
                Hydrostatic Pressure
                Biology and Life Sciences
                Anatomy
                Digestive System
                Pharynx
                Medicine and Health Sciences
                Anatomy
                Digestive System
                Pharynx
                Biology and Life Sciences
                Anatomy
                Respiratory System
                Pharynx
                Medicine and Health Sciences
                Anatomy
                Respiratory System
                Pharynx
                Medicine and Health Sciences
                Parasitic Diseases
                Nematode Infections
                Biology and Life Sciences
                Plant Science
                Plant Pathology
                Biology and Life Sciences
                Anatomy
                Digestive System
                Gastrointestinal Tract
                Rectum
                Medicine and Health Sciences
                Anatomy
                Digestive System
                Gastrointestinal Tract
                Rectum
                Biology and Life Sciences
                Anatomy
                Head
                Medicine and Health Sciences
                Anatomy
                Head
                Custom metadata
                All relevant data are within the paper and its Supporting Information files.

                Uncategorized

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