Plant Fungal Endosymbionts Alter Host-parasite Relationships Between Generalist Herbivores (Lepidoptera: Noctuidae) and an Entomopathogenic Nematode PDF Download
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Author: Brian Albert Kunkel
Publisher:
ISBN:
Category : Grasses
Languages : en
Pages : 0
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Book Description
Perennial ryegrass (Lolium perenne L.) and tall fescue (Festuca arundinacea Schreb.) contain symbiotic fungi (Neotyphodium spp.) that provide several ecological advantages to host plants: enhanced resistance to drought, disease, and insect herbivory. The resistance to insect herbivory is the result of fungus-produced alkaloids that are toxic to most herbivores. However, black cutworm, Agrotis ipsilon, is a generalist herbivore that is able to feed and develop on endophytic perennial ryegrass. As some insects can use plant secondary compounds to defend themselves against predators, I hypothesized that the cutworms fed on endophytic grasses would exhibit greater defense against a lethal endoparasitic nematode, Steinernema carpocapsae. To test this hypothesis, I developed a method to remove the fungal endophytes from the grass seed through a heat treatment. Laboratory experiments involving 4-5th instars support the hypothesis that A. ipsilon feeding on plants with high (>90%) incidence of endophyte are less susceptible to entomopathogenic nematodes than those feeding on plants with no or low incidence of endophyte. Field studies show decreased susceptibility to S. carpocapsae when larvae were confined to areas of endophytic grass (>75% infected). Early (2-3rd) instars were equally susceptible to nematode attack regardless of host plant. Endophytic grass fed to cutworm larvae did not influence nematode attachment behavior, or their ability to penetrate and successfully develop into adults. I examined the effects of ergot alkaloids that are produced by N. lolii such as, ergotamine, ergonovine, ergocryptine, ergocristine, and seed extract on nematode viability and infectivity. Ergonovine malate increased and ergocristine decreased the rates of nematode infectivity, whereas other treatments had no significant effect. I investigated the effects of ergocristine on Xenorhabdus nematophila, the symbiotic bacterium of S. carpocapsae. Bacterial growth and pathogenicity were significantly reduced when bacteria were grown in nutrient broth containing 200 g︡/ml concentration of ergocristine. Further research demonstrated that several fungal alkaloids, including ergocristine, persist in or are sequestered by black cutworm and another noctuid, the fall armyworm. I conclude that A. ipsilon developing on endophytic grasses may acquire some level of resistance against entomopathogenic nematodes. This resistance is mediated through the effects of alkaloids; thus our results underscore the ability of N. lolii to affect trophic interactions through the production of alkaloids.
Author: Brian Albert Kunkel
Publisher:
ISBN:
Category : Grasses
Languages : en
Pages : 0
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Book Description
Perennial ryegrass (Lolium perenne L.) and tall fescue (Festuca arundinacea Schreb.) contain symbiotic fungi (Neotyphodium spp.) that provide several ecological advantages to host plants: enhanced resistance to drought, disease, and insect herbivory. The resistance to insect herbivory is the result of fungus-produced alkaloids that are toxic to most herbivores. However, black cutworm, Agrotis ipsilon, is a generalist herbivore that is able to feed and develop on endophytic perennial ryegrass. As some insects can use plant secondary compounds to defend themselves against predators, I hypothesized that the cutworms fed on endophytic grasses would exhibit greater defense against a lethal endoparasitic nematode, Steinernema carpocapsae. To test this hypothesis, I developed a method to remove the fungal endophytes from the grass seed through a heat treatment. Laboratory experiments involving 4-5th instars support the hypothesis that A. ipsilon feeding on plants with high (>90%) incidence of endophyte are less susceptible to entomopathogenic nematodes than those feeding on plants with no or low incidence of endophyte. Field studies show decreased susceptibility to S. carpocapsae when larvae were confined to areas of endophytic grass (>75% infected). Early (2-3rd) instars were equally susceptible to nematode attack regardless of host plant. Endophytic grass fed to cutworm larvae did not influence nematode attachment behavior, or their ability to penetrate and successfully develop into adults. I examined the effects of ergot alkaloids that are produced by N. lolii such as, ergotamine, ergonovine, ergocryptine, ergocristine, and seed extract on nematode viability and infectivity. Ergonovine malate increased and ergocristine decreased the rates of nematode infectivity, whereas other treatments had no significant effect. I investigated the effects of ergocristine on Xenorhabdus nematophila, the symbiotic bacterium of S. carpocapsae. Bacterial growth and pathogenicity were significantly reduced when bacteria were grown in nutrient broth containing 200 g︡/ml concentration of ergocristine. Further research demonstrated that several fungal alkaloids, including ergocristine, persist in or are sequestered by black cutworm and another noctuid, the fall armyworm. I conclude that A. ipsilon developing on endophytic grasses may acquire some level of resistance against entomopathogenic nematodes. This resistance is mediated through the effects of alkaloids; thus our results underscore the ability of N. lolii to affect trophic interactions through the production of alkaloids.
Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 580
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Author: Muvari C. Tjiurutue
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Species interactions, by changing phenotypic traits, can alter the outcome of subsequent interactions. Plant-mediated responses to herbivores have been extensively studied, but little is known about plant-mediated responses involving parasitic plants within a broader community context that also includes herbivores. Because parasitic plants are important components of many ecosystems and can shape community structure, it is important to understand how host-mediated interactions influence parasite preference and success. The goal of this thesis is to examine interactions between hosts, parasitic plants and herbivores mediated by chemical traits. We first examined the effects of dodder (Cuscuta sp.) parasitism on induced defenses in cranberry, and asked how cranberry chemistry affected dodder preference and performance. We found dodder preference for some cultivars, and dodder parasitism induced many changes in cranberry chemistry, which could influence other interactions with cranberry hosts. We next examined the effects of gypsy moth herbivory on cranberry chemistry, and how plant-mediated changes affected subsequent dodder preference. Herbivory delayed and reduced the number of dodder plants that attached to cranberry hosts. Herbivory also induced changes in cranberry phenolic acids and phytohormones, which could mediate defenses against dodder parasitism. We also assessed the effects of previous herbivory (by tobacco hornworm or mechanical) and previous dodder parasitism on subsequent dodder preference on tomato hosts. Previous attachment followed by removal of dodder slowed subsequent dodder attachment on tomato hosts, but prior herbivory did not affect subsequent dodder attachment. Lastly, we asked whether damage to host induced changes in the host, and if attached parasites assimilated host defenses in response to host damage. Damage to host plants induces higher jasmonic acid in both hosts and attached parasites, and herbivores fed on leaves from parasites attached to damaged hosts ate more than herbivores fed on leaves attached to undamaged parasites. In summary, these studies demonstrate that parasites can induce changes in host responses that can potentially shape other interactions with the same hosts. Similarly, both herbivores and host responses can influence parasite preference, which could alter behavior of herbivores and pollinators, shaping community dynamics.
Author:
Publisher:
ISBN:
Category : Dissertation abstracts
Languages : en
Pages : 776
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Book Description
Author: Louis M. Schoonhoven
Publisher: Oxford University Press
ISBN: 019852594X
Category : Science
Languages : en
Pages : 441
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Book Description
"Half of all insect species are dependent on living plant tissues, consuming about 10% of plant annual production in natural habitats and an even greater percentage in agricultural systems, despite sophisticated control measures. Plants are generally remarkably well-protected against insect attack, with the result that most insects are highly specialized feeders. The mechanisms underlying plant resistance to invading herbivores on the one side, and insect food specialization on the other, are the main subjects of this book. For insects these include food-plant selection and the complex sensory processes involved, with their implications for learning and nutritional physiology, as well as the endocrinological aspects of life cycle synchronization with host plant phenology. In the case of plants exposed to insect herbivores, they include the activation of defence systems in order to minimize damage, as well as the emission of chemical signals that may attract natural enemies of the invading herbivores and may be exploited by neighbouring plants that mount defences as well." "Insect-Plant Biology discusses the operation of these mechanisms at the molecular and organismal levels, in the context of both ecological interactions and evolutionary relationships. In doing so, it uncovers the highly intricate antagonistic and mutualistic interactions that have evolved between plants and insects. The book concludes with a chapter on the application of our knowledge of insect-plant interactions to agricultural production." "This multidisciplinary approach will appeal to students in agricultural entomology, plant sciences, ecology, and indeed anyone interested in the principles underlying the relationships between the two largest groups of organisms on earth: plants and insects."--BOOK JACKET.Title Summary field provided by Blackwell North America, Inc. All Rights Reserved
Author: Jacques Brodeur
Publisher: Springer Science & Business Media
ISBN: 1402047673
Category : Science
Languages : en
Pages : 257
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Book Description
This volume explores modern concepts of trophic and guild interactions among natural enemies in natural and agricultural ecosystems - a field that has become a hot topic in ecology and biological control over the past decade. It is the first book on trophic and guild interactions to make the link to biological control, and is compiled by internationally recognized scientists who have combined their expertise.
Author: Ajit Varma
Publisher: Springer Science & Business Media
ISBN: 3540958940
Category : Science
Languages : en
Pages : 444
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Book Description
Symbiotic Fungi – Principles and Practice presents current protocols for the study of symbiotic fungi and their interactions with plant roots, such as techniques for analyzing nutrient transfer, ecological restoration, microbial communication, and mycorrhizal bioassays, AM inoculum procedures and mushroom technology. The protocols offer practical solutions for researchers and students involved in the study of symbiotic microorganisms. The volume will be of great use for basic research, biotechnological applications, and the development of commercial products.
Author: James F. White Jr.
Publisher: CRC Press
ISBN: 1420069322
Category : Science
Languages : en
Pages : 436
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Book Description
Anemones and fish, ants and acacia trees, fungus and trees, buffaloes and oxpeckers--each of these unlikely duos is an inimitable partnership in which the species' coexistence is mutually beneficial. More specifically, they represent examples of defensive mutualism, when one species receives protection against predators or parasites in exchange for
Author: A. Ciancio
Publisher: Springer Science & Business Media
ISBN: 1402060610
Category : Science
Languages : en
Pages : 366
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Book Description
This, the first volume of the ‘Integrated Management of Plant Pests and Diseases’ book series, presents general concepts on integrated pest and disease management. Section one includes chapters on infection models, resurgence and replacement, plant disease epidemiology and effects of climate change in tropical environments. The second section includes remote sensing and information technology. Finally, the third section covers molecular aspects of the subject.
Author: Gillian A. Cooper-Driver
Publisher: Springer
ISBN: 9780306420061
Category : Science
Languages : en
Pages : 260
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Book Description
Plant detection of pathogens. Biochemical aspects of plant-microbe and microbe-microbe interaction in soil. Biochemical responses of plants to fungal attack. Allelopathy - an overview. Plant allelochemicals: linkages between herbivores and their natural enemies. Brementown revisited: interactions among allelochemicals in plants. Multifaceted chemically based resistance in plants. Pheromonal communication between plants. Adaptation to resource availability as a determinant of chemical defense strategies in woody plants.
