Schlüsselwörter
(Englisch)
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endosybiont; Wolbachia; Biological control; mites; Acari
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Forschungsprogramme
(Englisch)
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COST-Action FA0701 - Arthropod Symbioses: from fundamental studies to pest and disease management
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Kurzbeschreibung
(Englisch)
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Mites are widespread and exhibit very different life styles. Pest and beneficial mites are of major importance in agricultural environments all over the world. Among the crop-pests spider mites are the most important family, comprising more than 1200 known species which are capable to damage a wide range of agricultural crops such as fruit trees, berries, vegetables, field crops and ornamentals. Many species are parasites of domestic animals (livestock, poultry, companion animals, honey bees) and humans. Maternally-inherited endosymbiont bacteria are very widespread among arthropod species. The most studied endosymbiont Wolbachia infects 20-70% of arthropod species. To ensure their spread within their host's populations, these bacteria evolved four different strategies to improve the fitness of infected females in comparison to un-infected ones. These reproduction manipulation strategies are parthenogenesis induction, cytoplasmic incompatibility, feminization and male-killing. While endosymbionts may have an effect on the population dynamics of a crop-pest species, it has only recently been suggested that such bacteria-host association could be used to achieve pest or disease vector biological control The two former strategies can potentially be used in biological control. Parthenogenesis induction could be used to improve the efficacy and the rearing of a beneficial agent while cytoplasmic incompatibility could be used to deplete a pest species population (a strategy similar to the sterile insect technique). The very few studies investigating the endosymbiont community in mite species suggest that 17 - 58% of the species are infected by at least one bacteria species. Behavioural studies showed that these endosymbionts were inducing parthenogenesis or cytoplasmic incompatibilities in their mite hosts. By a combination of molecular screen and behavioural analysis this project aims to i) characterize the endosymbiont community associated with a wide variety of mites,
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Weitere Hinweise und Angaben
(Englisch)
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Full name of research-institution/enterprise: Forschungsanstalt Agroscope Reckenholz-Tänikon ART Biodiversity and Environmental Management, Biosafety
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Partner und Internationale Organisationen
(Englisch)
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AT, CH, CZ, DE, DK, ES, FR, GR, HU, IE, IL, IT, NL, NO, PL, PT, RS, SE, SI, UK
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Abstract
(Englisch)
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The microbiome associated with arthropods is very diverse and may significantly influence the biology of biological biocontrol agents and arthropod pests. Some endosymbiont bacteria may even be usedto achieve pest or disease vector biological control. The subclass Acari (mites and ticks) is very diverse in form, habitat and behaviour. Mites can be plant pests, parasites of domestic animals and humans or predators of major crop-pests. The aim of this first chapter was to collect and present an overview of the present literature and knowledge on the prevalence and distribution of maternally-inherited ES (Arsenophonus spp., Cardinium spp., Flavobacteria spp., Rickettsia spp., Spiroplasma spp. and Wolbachia spp.) in mite species (chapter 1). We completed this knowledge by adding the results of our own screening (chapter 3), including mite species of three different lifestyles (herbivorous, predatory and parasitic). We found that mites and their ES have been studied, but the focus has clearly been on presence and distribution of insect ES in spider mites, whereas many other mite families as well as the further characterization of effects of ES on their hosts have received less attention. As a next step we describe the different ways microorganisms associated with arthropods can have an influence on biological pest- and disease vector control, through the many ways they can be involved in their hosts biology and we then provide practical recommendations on the handling of ES in biological control agents and pests (chapter 2). The bulb mite Rhizoglyhus robini is below-ground pest mostly on Liliacean crop plants, which has been observed mainly on plants already infested with a fungus. As not many animals carry the enzymatic machinery to digest fungal carbohydrates, we tested the hypothesis that associated bacteria are involved in the chitin digetion. Preliminary DGGE assessment with general bacterial primers, revealed a high diversity. Investigating the bacterial community associated with this mite in more detail by 454 metagenomic analysis, we found several genera which contain chitin-degrading species. Bioassays confirmed the mite's preference for - and high fitness on - a fungal food source. Finally we could make the link between the fungal food source of the mite and the bacterial chitinolytic ability by demonstrating the digestion of chitin by mite homogenate and isolating bacteria from the chitin-free zones (chapter 4). We molecularly identified these isolated clones as Serratia marcescens (chapter 5), a bacterium well known for its chitinolytic machinery. The biology of Rhizoglyphus robini can be understood only if the associated bacteria are also considered. The mites' status has to be reassessed now, as it was previously described as a primary pest, feeding on the bulbs and tubers of plants. If the mite attacks plants preferentially after previous plant- infection with a fungus, this could be exploited in biological control. The fact that the mite might need the bacteria to digest the fungus also opens up new possibilities for control of the mite. We believe that the bacterial community in most pest and beneficial mites will deliver valuable information, which can be used in the development of new control strategies or to explain and potentially solve problems in existing control programs (chapter 2). In chapter two we explain in detail why we recommend including an investigation of the associated microbiome in standard assessments of pests and control agents.
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Datenbankreferenzen
(Englisch)
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Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. +41 31 322 74 82 Swiss Project-Number: C08.0109
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