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C R Wilson - One of the best experts on this subject based on the ideXlab platform.
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Moments of weaknesses - exploiting vulnerabilities between germination and encystment in the Phytomyxea
'Wiley', 2021Co-Authors: Amponsah J, R S Tegg, Thangavel T, C R WilsonAbstract:Attempts at management of diseases caused by protozoan plant parasitic Phytomyxea have often been ineffective. The dormant life stage is characterised by long-lived highly robust Resting Spores that are largely impervious to chemical treatment and environmental stress. This review explores some life stage weaknesses and highlights possible control measures associated with Resting Spore germination and zooSpore taxis. With phytomyxid pathogens of agricultural importance, zooSpore release from Resting Spores is stimulated by plant root exudates. On germination, the zooSpores are attracted to host roots by chemoattractant components of root exudates. Both the relatively metabolically inactive Resting Spore and motile zooSpore need to sense the chemical environment to determine the suitability of these germination stimulants or attractants respectively, before they can initiate an appropriate response. Blocking such sensing could inhibit Resting Spore germination or zooSpore taxis. Conversely, the short life span and the vulnerability of zooSpores to the environment require them to infect their host within a few hours after release. Identifying a mechanism or conditions that could synchronise Resting Spore germination in the absence of host plants could lead to diminished pathogen populations in the field
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Quantitative proteomics provides an insight into germination-related proteins in the obligate biotrophic plant pathogen Spongospora subterranea
'Wiley', 2021Co-Authors: Balotf S, R S Tegg, Wilson R, Ds Nichols, C R WilsonAbstract:The soil-borne and obligate plant-associated nature of S. subterranea has hindered a detailed study of this pathogen and in particular, the regulatory pathways driving the germination of S. subterranea remain unknown. To better understand the mechanisms that control the transition from dormancy to germination, protein profiles between dormant and germination stimulant-treated Resting Spores were compared using label-free quantitative proteomics. Among the ~680 proteins identified 20 proteins were found to be differentially expressed during the germination of S. subterranea Resting Spores. Elongation factor Tu, histones (H2A and H15), proteasome and DJ-1_PfpI, involved in transcription and translation, were upregulated during the germination of Resting Spores. Downregulation of both actin and beta-tubulin proteins occurred in the germinating Spores, indicating that the changes in the cell wall cytoskeleton may be necessary for the morphological changes during the germination of the Resting Spore in S. subterranea. Our findings provide new approaches for the study of these and similar recalcitrant micro-organisms provide the first insights into the basic protein components of S. subterranea Spores. A better understanding of S. subterranea biology may lead to the development of novel approaches for the management of persistent soil inoculum
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germinate to exterminate chemical stimulation of spongospora subterranea Resting Spore germination and its potential to diminish soil inoculum
Plant Pathology, 2018Co-Authors: Mark Angelo Balendres, R S Tegg, T J Clark, C R WilsonAbstract:Hoagland’s solution (HS), a defined nutrient supplement for plants, has been previously reported to stimulate zooSpore release from Resting Spores of the potato pathogen Spongospora subterranea f. sp. subterranea. This study obtained direct empirical evidence for an increase in zooSpore release with HS treatment, and identified Fe-EDTA as the stimulant component of HS. Stimulation of Resting Spores by HS and Fe-EDTA resulted in greater and earlier zooSpore release compared to a distilled water control, and in the presence of a susceptible tomato host plant resulted in enhanced root infection. Given the labile nature of S. subterranea zooSpores, it was postulated that stimulation of premature release of zooSpores from the dormant Resting Spores in absence of susceptible hosts could reduce soil inoculum levels. In two glasshouse trials in the absence of host plants, both Fe-EDTA and HS soil treatments reduced S. subterranea soil inoculum levels, providing proof of concept for the ‘germinate to exterminate’ approach to inoculum management.
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Resting Spore dormancy and infectivity characteristics of the potato powdery scab pathogen spongospora subterranea
Journal of Phytopathology, 2017Co-Authors: Mark Angelo Balendres, R S Tegg, C R WilsonAbstract:The soil-borne potato pathogen Spongospora subterranea persists in soil as sporosori, which are aggregates of Resting Spores. Resting Spores may germinate in the presence of plant or environmental stimuli, but direct evidence for Resting Spore dormancy is limited. A soilless tomato bait plant bioassay and microscopic examination were used to examine features of S. subterranea Resting Spore dormancy and infectivity. Dried sporosori inocula prepared from tuber lesions and root galls were infective after both short- and long-term storage (1 week to 5 years for tuber lesions and 1 week to 1 year for root galls) with both young and mature root galls inocula showing infectivity. This demonstrated that a proportion of all S. subterranea Resting Spores regardless of maturity exhibit characteristics of stimuli-responsive dormancy, germinating under the stimulatory conditions of the bait host plant bioassay. However, evidence for constitutive dormancy within the Resting Spore population was also provided as incubation of sporosorus inoculum in a germination-stimulating environment did not fully exhaust germination potential even after 2.4 years. We conclude that S. subterranea sporosori contain both exogenous (stimuli-responsive) and constitutively dormant Resting Spores, which enables successful host infection by germination in response to plant stimuli and long-term persistence in the soil.
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potato root exudation and release of spongospora subterranea Resting Spore germination stimulants are affected by plant and environmental conditions
Journal of Phytopathology, 2017Co-Authors: Mark Angelo Balendres, R S Tegg, David Nichols, C R WilsonAbstract:Variation in plant and environmental conditions were studied to determine the effect thereof on the exudation of low-molecular-weight organic compounds by potato roots. The results of the phytochemical analyses showed that among the conditions investigated, root vigour, potato cultivar, nutrients in incubation solution and temperature influenced the number and the type of primary metabolites released. Moreover, these conditions influenced our detection of compounds known to stimulate germination of Resting Spores of the pathogen Spongospora subterranea, causal agent of powdery scab and root diseases of potato. We conclude that changes in plant and environmental conditions can affect the release of specific compounds that stimulate germination of S. subterranea Resting Spores. The impact of the factors affecting potato root exudation on subsequent disease development is discussed.
Ingeborg Klingen - One of the best experts on this subject based on the ideXlab platform.
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Research Article Abiotic and Biotic Factors Affecting Resting Spore Formation in the Mite Pathogen Neozygites floridana
2016Co-Authors: Vanessa Da Silveira Duarte, Ingeborg Klingen, Karin Westrum, Ana Elizabete Lopes Ribeiro, Manoel Guedes, Corrêa Gondim, Italo Delalibera JúniorAbstract:Copyright © 2013 Vanessa da Silveira Duarte et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Neozygites floridana is an obligate mite pathogenic fungus in the Entomophthoromycota. It has been suggested that Resting Spores of this fungus are produced as a strategy to survive adverse conditions. In the present study, possible mechanisms involved in the regulation of Resting Spore formation were investigated in the hosts Tetranychus urticae and Tetranychus evansi. Abiotic and biotic factors mimicking conditions that we, based on earlier field studies, thought might induce Resting Spores in temperate and tropical regions were testedwith isolates fromNorway and Brazil. A total of 42 combinations of conditions were tested, but only one induced the formation of a high number of Resting Spores in only one isolate. The Brazilian isolate ESALQ1420 produced a large number of Resting Spores (51.5%) in T. urticae at a temperature of 11∘C, photoperiod of 10L:14D, and light intensity of 42–46
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confirmation of neozygites floridana azygoSpore formation in two spotted spider mite tetranychus urticae in strains from tropical and temperate regions
Journal of Invertebrate Pathology, 2014Co-Authors: Karin Westrum, Vanessa Da Silveira Duarte, Richard A. Humber, Ingeborg KlingenAbstract:Abstract Neozygites floridana is an obligate fungal pathogen of mites in the family Tetranychidae and is an important natural enemy of the two-spotted spider mite (Tetranychus urticae). Until now, information about the formation of azygoSpores remained to be fully confirmed. In this study, we document the formation of azygoSpores by a Brazilian N. floridana strain and the formation of azygoSpores and zygoSpores by a Norwegian N. floridana strain, both in the host T. urticae. Evidence of both zygosporogenesis and azygosporogenesis was also found in the same individual in the Norwegian stains. Further we report the presence of immature azygoSpores with 1–3 nuclei for the Norwegian strains, immature Resting Spores (probably azygoSpores) with 1–8 nuclei for the Brazilian strain, and mature Resting Spores with 2 nuclei for both the Norwegian and the Brazilian strains (azygo- or zygoSpores). Our observations suggest that the immature Resting Spore (preSpore) of both strains begins in a multinucleate condition but that the nuclear number is reduced during maturation until mature Resting Spore is binucleate regardless of its origin as a zygoSpore or azygoSpore.
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abiotic and biotic factors affecting Resting Spore formation in the mite pathogen neozygites floridana
International Journal of Microbiology, 2013Co-Authors: Vanessa Da Silveira Duarte, Ana Elizabete Lopes Ribeiro, Karin Westrum, Manoel Guedes Correa Gondim, Ingeborg KlingenAbstract:Neozygites floridana is an obligate mite pathogenic fungus in the Entomophthoromycota. It has been suggested that Resting Spores of this fungus are produced as a strategy to survive adverse conditions. In the present study, possible mechanisms involved in the regulation of Resting Spore formation were investigated in the hosts Tetranychus urticae and Tetranychus evansi. Abiotic and biotic factors mimicking conditions that we, based on earlier field studies, thought might induce Resting Spores in temperate and tropical regions were tested with isolates from Norway and Brazil. A total of 42 combinations of conditions were tested, but only one induced the formation of a high number of Resting Spores in only one isolate. The Brazilian isolate ESALQ1420 produced a large number of Resting Spores (51.5%) in T. urticae at a temperature of 11°C, photoperiod of 10L:14D, and light intensity of 42–46 (μmol m−2 s−1) on nonsenescent plants (nondiapausing females). Resting Spores of the Brazilian N. floridana isolate ESALQ1421 were found at very low levels (up to 1.0%). Small percentages of T. urticae with Resting Spores (0–5.0%) were found for the Norwegian isolate NCRI271/04 under the conditions tested. The percentages of Resting Spores found for the Norwegian isolate in our laboratory studies are similar to the prevalence reported in earlier field studies.
Mark Angelo Balendres - One of the best experts on this subject based on the ideXlab platform.
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germinate to exterminate chemical stimulation of spongospora subterranea Resting Spore germination and its potential to diminish soil inoculum
Plant Pathology, 2018Co-Authors: Mark Angelo Balendres, R S Tegg, T J Clark, C R WilsonAbstract:Hoagland’s solution (HS), a defined nutrient supplement for plants, has been previously reported to stimulate zooSpore release from Resting Spores of the potato pathogen Spongospora subterranea f. sp. subterranea. This study obtained direct empirical evidence for an increase in zooSpore release with HS treatment, and identified Fe-EDTA as the stimulant component of HS. Stimulation of Resting Spores by HS and Fe-EDTA resulted in greater and earlier zooSpore release compared to a distilled water control, and in the presence of a susceptible tomato host plant resulted in enhanced root infection. Given the labile nature of S. subterranea zooSpores, it was postulated that stimulation of premature release of zooSpores from the dormant Resting Spores in absence of susceptible hosts could reduce soil inoculum levels. In two glasshouse trials in the absence of host plants, both Fe-EDTA and HS soil treatments reduced S. subterranea soil inoculum levels, providing proof of concept for the ‘germinate to exterminate’ approach to inoculum management.
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Resting Spore dormancy and infectivity characteristics of the potato powdery scab pathogen spongospora subterranea
Journal of Phytopathology, 2017Co-Authors: Mark Angelo Balendres, R S Tegg, C R WilsonAbstract:The soil-borne potato pathogen Spongospora subterranea persists in soil as sporosori, which are aggregates of Resting Spores. Resting Spores may germinate in the presence of plant or environmental stimuli, but direct evidence for Resting Spore dormancy is limited. A soilless tomato bait plant bioassay and microscopic examination were used to examine features of S. subterranea Resting Spore dormancy and infectivity. Dried sporosori inocula prepared from tuber lesions and root galls were infective after both short- and long-term storage (1 week to 5 years for tuber lesions and 1 week to 1 year for root galls) with both young and mature root galls inocula showing infectivity. This demonstrated that a proportion of all S. subterranea Resting Spores regardless of maturity exhibit characteristics of stimuli-responsive dormancy, germinating under the stimulatory conditions of the bait host plant bioassay. However, evidence for constitutive dormancy within the Resting Spore population was also provided as incubation of sporosorus inoculum in a germination-stimulating environment did not fully exhaust germination potential even after 2.4 years. We conclude that S. subterranea sporosori contain both exogenous (stimuli-responsive) and constitutively dormant Resting Spores, which enables successful host infection by germination in response to plant stimuli and long-term persistence in the soil.
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potato root exudation and release of spongospora subterranea Resting Spore germination stimulants are affected by plant and environmental conditions
Journal of Phytopathology, 2017Co-Authors: Mark Angelo Balendres, R S Tegg, David Nichols, C R WilsonAbstract:Variation in plant and environmental conditions were studied to determine the effect thereof on the exudation of low-molecular-weight organic compounds by potato roots. The results of the phytochemical analyses showed that among the conditions investigated, root vigour, potato cultivar, nutrients in incubation solution and temperature influenced the number and the type of primary metabolites released. Moreover, these conditions influenced our detection of compounds known to stimulate germination of Resting Spores of the pathogen Spongospora subterranea, causal agent of powdery scab and root diseases of potato. We conclude that changes in plant and environmental conditions can affect the release of specific compounds that stimulate germination of S. subterranea Resting Spores. The impact of the factors affecting potato root exudation on subsequent disease development is discussed.
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biology and chemical ecology of spongospora subterranea during Resting Spore germination towards a germinate exterminate control approach for spongospora diseases of potato
2017Co-Authors: Mark Angelo BalendresAbstract:Resting Spores are important for the spread and survival of Spongospora subterranea, the causative agent of potato powdery scab and root disease. However, Resting Spores must germinate and release zooSpores (the infective agents) to cause infection. Understanding of the germination process and factors is, therefore, important. The knowledge can potentially have implications for Resting Spore-inoculum management and Spongospora disease control. The biology and ecology of S. subterranea during Resting Spore germination is not well understood. Knowledge of factors influencing Resting Spore germination have been limited. This thesis studied the properties of S. subterranea Resting Spores and investigated some chemical factors stimulating Resting Spore germination. The role of germination-chemical stimulants was also examined. This study used a combination of tomato-plant and zooSpore in vitro bioassays, light microscopy, a targeted hydrophilic interaction ultra-high performance liquid chromatography–mass spectrometry metabolomic approach, and a greenhouse chemical-soil treatment study. Some of S. subterranea Resting Spores exhibited dormant Spore characteristics, which required specific stimuli to germinate. Although a proportion retains constitutive dormancy characteristics, chemical germination-stimulants were found in potato root exudates and in Hoagland’s solution. The low-molecular weight organic amino acids – tyramine and L-glutamine – and sugars – cellobiose and L-rhamnose – compounds stimulated Resting Spore germination at 0.1 mg/ml solution. The release of these compounds in potato roots were influenced by the plant’s physiology and growth conditions. Hoagland’s solution contains Iron-EDTA, which stimulated Resting Spore germination. Germination stimulant Fe-EDTA, in Hoagland’s solution, in the presence a susceptible host plant, enhanced root infection. However, Fe-EDTA and Hoagland’s solution added into S. subterranea-infested soil, a month prior to planting, reduced pathogen inoculum DNA levels in the soil. Further field studies underpinning the use of germination stimulant compounds could lead to a novel, safe and sustainable chemical approach for the management of S. subterranea inoculum in the soil and thus will augment other Spongospora disease control measures. This thesis advances our understanding of S. subterranea biology and chemical ecology during Resting Spore germination. Substantial development is now beginning to be made in the facet of Resting Spore germination biology and chemical ecology, which are important aspects of Spongospora disease epidemiology and disease control development. There remains much to be learned, but the knowledge presented here will encourage additional studies and research efforts. Powdery scab, Spongospora root infection, plasmodiophorid, chemical ecology, potato metabolomics, HILIC UHPLC-MS, Resting Spore germination, Spore dormancy.
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metabolomes of potato root exudates compounds that stimulate Resting Spore germination of the soil borne pathogen spongospora subterranea
Journal of Agricultural and Food Chemistry, 2016Co-Authors: Mark Angelo Balendres, R S Tegg, David Nichols, C R WilsonAbstract:Root exudation has importance in soil chemical ecology influencing rhizosphere microbiota. Prior studies reported root exudates from host and nonhost plants stimulated Resting Spore germination of Spongospora subterranea, the powdery scab pathogen of potato, but the identities of stimulatory compounds were unknown. This study showed that potato root exudates stimulated S. subterranea Resting Spore germination, releasing more zooSpores at an earlier time than the control. We detected 24 low molecular weight organic compounds within potato root exudates and identified specific amino acids, sugars, organic acids, and other compounds that were stimulatory to S. subterranea Resting Spore germination. Given that several stimulatory compounds are commonly found in exudates of diverse plant species, we support observations of nonhost-specific stimulation. We provide knowledge of S. subterranea Resting Spore biology and chemical ecology that may be useful in formulating new disease management strategies.
Vanessa Da Silveira Duarte - One of the best experts on this subject based on the ideXlab platform.
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Research Article Abiotic and Biotic Factors Affecting Resting Spore Formation in the Mite Pathogen Neozygites floridana
2016Co-Authors: Vanessa Da Silveira Duarte, Ingeborg Klingen, Karin Westrum, Ana Elizabete Lopes Ribeiro, Manoel Guedes, Corrêa Gondim, Italo Delalibera JúniorAbstract:Copyright © 2013 Vanessa da Silveira Duarte et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Neozygites floridana is an obligate mite pathogenic fungus in the Entomophthoromycota. It has been suggested that Resting Spores of this fungus are produced as a strategy to survive adverse conditions. In the present study, possible mechanisms involved in the regulation of Resting Spore formation were investigated in the hosts Tetranychus urticae and Tetranychus evansi. Abiotic and biotic factors mimicking conditions that we, based on earlier field studies, thought might induce Resting Spores in temperate and tropical regions were testedwith isolates fromNorway and Brazil. A total of 42 combinations of conditions were tested, but only one induced the formation of a high number of Resting Spores in only one isolate. The Brazilian isolate ESALQ1420 produced a large number of Resting Spores (51.5%) in T. urticae at a temperature of 11∘C, photoperiod of 10L:14D, and light intensity of 42–46
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confirmation of neozygites floridana azygoSpore formation in two spotted spider mite tetranychus urticae in strains from tropical and temperate regions
Journal of Invertebrate Pathology, 2014Co-Authors: Karin Westrum, Vanessa Da Silveira Duarte, Richard A. Humber, Ingeborg KlingenAbstract:Abstract Neozygites floridana is an obligate fungal pathogen of mites in the family Tetranychidae and is an important natural enemy of the two-spotted spider mite (Tetranychus urticae). Until now, information about the formation of azygoSpores remained to be fully confirmed. In this study, we document the formation of azygoSpores by a Brazilian N. floridana strain and the formation of azygoSpores and zygoSpores by a Norwegian N. floridana strain, both in the host T. urticae. Evidence of both zygosporogenesis and azygosporogenesis was also found in the same individual in the Norwegian stains. Further we report the presence of immature azygoSpores with 1–3 nuclei for the Norwegian strains, immature Resting Spores (probably azygoSpores) with 1–8 nuclei for the Brazilian strain, and mature Resting Spores with 2 nuclei for both the Norwegian and the Brazilian strains (azygo- or zygoSpores). Our observations suggest that the immature Resting Spore (preSpore) of both strains begins in a multinucleate condition but that the nuclear number is reduced during maturation until mature Resting Spore is binucleate regardless of its origin as a zygoSpore or azygoSpore.
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abiotic and biotic factors affecting Resting Spore formation in the mite pathogen neozygites floridana
International Journal of Microbiology, 2013Co-Authors: Vanessa Da Silveira Duarte, Ana Elizabete Lopes Ribeiro, Karin Westrum, Manoel Guedes Correa Gondim, Ingeborg KlingenAbstract:Neozygites floridana is an obligate mite pathogenic fungus in the Entomophthoromycota. It has been suggested that Resting Spores of this fungus are produced as a strategy to survive adverse conditions. In the present study, possible mechanisms involved in the regulation of Resting Spore formation were investigated in the hosts Tetranychus urticae and Tetranychus evansi. Abiotic and biotic factors mimicking conditions that we, based on earlier field studies, thought might induce Resting Spores in temperate and tropical regions were tested with isolates from Norway and Brazil. A total of 42 combinations of conditions were tested, but only one induced the formation of a high number of Resting Spores in only one isolate. The Brazilian isolate ESALQ1420 produced a large number of Resting Spores (51.5%) in T. urticae at a temperature of 11°C, photoperiod of 10L:14D, and light intensity of 42–46 (μmol m−2 s−1) on nonsenescent plants (nondiapausing females). Resting Spores of the Brazilian N. floridana isolate ESALQ1421 were found at very low levels (up to 1.0%). Small percentages of T. urticae with Resting Spores (0–5.0%) were found for the Norwegian isolate NCRI271/04 under the conditions tested. The percentages of Resting Spores found for the Norwegian isolate in our laboratory studies are similar to the prevalence reported in earlier field studies.
Karin Westrum - One of the best experts on this subject based on the ideXlab platform.
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Research Article Abiotic and Biotic Factors Affecting Resting Spore Formation in the Mite Pathogen Neozygites floridana
2016Co-Authors: Vanessa Da Silveira Duarte, Ingeborg Klingen, Karin Westrum, Ana Elizabete Lopes Ribeiro, Manoel Guedes, Corrêa Gondim, Italo Delalibera JúniorAbstract:Copyright © 2013 Vanessa da Silveira Duarte et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Neozygites floridana is an obligate mite pathogenic fungus in the Entomophthoromycota. It has been suggested that Resting Spores of this fungus are produced as a strategy to survive adverse conditions. In the present study, possible mechanisms involved in the regulation of Resting Spore formation were investigated in the hosts Tetranychus urticae and Tetranychus evansi. Abiotic and biotic factors mimicking conditions that we, based on earlier field studies, thought might induce Resting Spores in temperate and tropical regions were testedwith isolates fromNorway and Brazil. A total of 42 combinations of conditions were tested, but only one induced the formation of a high number of Resting Spores in only one isolate. The Brazilian isolate ESALQ1420 produced a large number of Resting Spores (51.5%) in T. urticae at a temperature of 11∘C, photoperiod of 10L:14D, and light intensity of 42–46
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confirmation of neozygites floridana azygoSpore formation in two spotted spider mite tetranychus urticae in strains from tropical and temperate regions
Journal of Invertebrate Pathology, 2014Co-Authors: Karin Westrum, Vanessa Da Silveira Duarte, Richard A. Humber, Ingeborg KlingenAbstract:Abstract Neozygites floridana is an obligate fungal pathogen of mites in the family Tetranychidae and is an important natural enemy of the two-spotted spider mite (Tetranychus urticae). Until now, information about the formation of azygoSpores remained to be fully confirmed. In this study, we document the formation of azygoSpores by a Brazilian N. floridana strain and the formation of azygoSpores and zygoSpores by a Norwegian N. floridana strain, both in the host T. urticae. Evidence of both zygosporogenesis and azygosporogenesis was also found in the same individual in the Norwegian stains. Further we report the presence of immature azygoSpores with 1–3 nuclei for the Norwegian strains, immature Resting Spores (probably azygoSpores) with 1–8 nuclei for the Brazilian strain, and mature Resting Spores with 2 nuclei for both the Norwegian and the Brazilian strains (azygo- or zygoSpores). Our observations suggest that the immature Resting Spore (preSpore) of both strains begins in a multinucleate condition but that the nuclear number is reduced during maturation until mature Resting Spore is binucleate regardless of its origin as a zygoSpore or azygoSpore.
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abiotic and biotic factors affecting Resting Spore formation in the mite pathogen neozygites floridana
International Journal of Microbiology, 2013Co-Authors: Vanessa Da Silveira Duarte, Ana Elizabete Lopes Ribeiro, Karin Westrum, Manoel Guedes Correa Gondim, Ingeborg KlingenAbstract:Neozygites floridana is an obligate mite pathogenic fungus in the Entomophthoromycota. It has been suggested that Resting Spores of this fungus are produced as a strategy to survive adverse conditions. In the present study, possible mechanisms involved in the regulation of Resting Spore formation were investigated in the hosts Tetranychus urticae and Tetranychus evansi. Abiotic and biotic factors mimicking conditions that we, based on earlier field studies, thought might induce Resting Spores in temperate and tropical regions were tested with isolates from Norway and Brazil. A total of 42 combinations of conditions were tested, but only one induced the formation of a high number of Resting Spores in only one isolate. The Brazilian isolate ESALQ1420 produced a large number of Resting Spores (51.5%) in T. urticae at a temperature of 11°C, photoperiod of 10L:14D, and light intensity of 42–46 (μmol m−2 s−1) on nonsenescent plants (nondiapausing females). Resting Spores of the Brazilian N. floridana isolate ESALQ1421 were found at very low levels (up to 1.0%). Small percentages of T. urticae with Resting Spores (0–5.0%) were found for the Norwegian isolate NCRI271/04 under the conditions tested. The percentages of Resting Spores found for the Norwegian isolate in our laboratory studies are similar to the prevalence reported in earlier field studies.