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  • 1
    Publication Date: 2011-08-01
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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  • 2
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    SPRINGER HEIDELBERG
    In:  EPIC3Mycological Progress, SPRINGER HEIDELBERG, 19(5), pp. 441-454, ISSN: 1617-416X
    Publication Date: 2020-05-04
    Description: Oomycetes infecting diatoms are biotrophic parasitoids and live in both marine and freshwater environments. They are ubiquitous, but the taxonomic affinity of many species remains unclear and the majority of them have not been studied for their molecular phylogeny. Only recently, the phylogenetic and taxonomic placement of some diatom-infecting, early-diverging oomycetes was resolved, including the genera Ectrogella, Miracula, Olpidiopsis, and Pontisma. A group of holocarpic diatom parasitoids with zoospores swarming within the sporangium before release were found to be unrelated to the known genera with diatom-infecting species, and were re-classified to a new genus, Diatomophthora. However, about a dozen species of holocarpic diatom parasitoids with unclear affinity remained unsequenced, which includes a commonly occurring species so far identified as Ectrogella perforans. However, this assignment to Ectrogella is doubtful, as the species was not reported to feature a clear-cut diplanetism, a hallmark of Ectrogella s. str. and the whole class Saprolegniomycetes. It was the aim of the current study to clarify the phylogenetic affinities of the species and if the rather broad host range reported is correct or a reflection of cryptic species. By targeted screening, the parasitoid was rediscovered from Helgoland Roads, North Sea and Oslo Fjord, Southern Norway and investigated for its phylogenetic placement using small ribosomal subunit (18S) sequences. Stages of its life cycle on different marine diatoms were described and its phylogenetic placement in the genus Diatomophthora revealed. A stable host-parasite axenic culture from single spore strains of the parasitoid were established on several strains of Pleurosigma intermedium and Coscinodiscus concinnus. These have been continuously cultivated along with their hosts for more than 2 years, and cultural characteristics are reported. Cross-infection trials revealed the transferability of the strains between hosts under laboratory conditions, despite some genetic distance between the pathogen strains. Thus, we hypothesise that D. perforans might be in the process of active radiation to new host species.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 3
    Publication Date: 2019-11-28
    Description: Despite their widespread nature and economic impact, little is known regarding the diversity and phylogeny of diatom-infecting oomycetes. While the phylogenetic affinities of Lagenisma, affecting large centric diatoms, has recently been resolved, no member of the widespread genus Ectrogella has, so far, been investigated using molecular phylogenetics. The genus Ectrogella contains about a dozen species, which are all holocarpic. The species in the genus are diverse in terms of morphology and development, and primarily set apart from other holocarpic oomycete genera on the basis of their occurrence in unicellular or colonial algae, predominantly licmophoroid and bacillarioid diatoms. Here, we report the phylogenetic placement of two oomycete parasitoids one parasitic to Pseudo-nitzschia pungens and the other parasitic to Rhizosolenia imbricata. While both parasitoids were placed outside the crown oomycete groups represented by Saprolegniomycetes and Peronosporomycetes, they did not form a monophyletic assemblage. The Rhizosolenia parasitoid was embedded amongst marine Olpidiopsis species, while the Pseudo-nitzschia parasitoid was placed as the sister clade to all remaining oomycetes. The taxonomy of Ectrogella-like organisms and Olpidiopsis is discussed and, as a consequence of morphological differences and phylogenetic placement, two new species, Miracula helgolandica and Olpidiopsis drebesii, are introduced.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 4
    Publication Date: 2024-01-12
    Description: The obligate biotrophic lineages of the white blister rusts (Albuginales, Oomycota) are of ancient origin compared to the rather recently evolved downy mildews, and sophisticated mechanisms of biotrophy and a high degree of adaptation diversity are to be expected in these organisms. Speciation in the biotrophic Oomycetes is usually thought to be the consequence of host adaptation or geographic isolation. Here we report the presence of two distinct species of Albugo on the model plant Arabidopsis thaliana, Albugo candida and Albugo laibachii, the latter being formally described in this manuscript. Both species may occupy the same host within the same environment, but are nevertheless phylogenetically distinct, as inferred from analyses of both mitochondrial and nuclear DNA sequences. Different ways of adapting to their host physiology might constitute an important factor of their different niches. Evidence for this can be gained from the completely different host range of the two pathogens.\nWhile Albugo candida is a generalist species, consisting of several physiological varieties, which is able to parasitize a great variety of Brassicaceae, Albugo laibachii has not been found on any host other than Arabidopsis thaliana.\nTherefore, Albugo laibachii belongs to a group of highly specialised species, like the other known specialist species in Albugo s.s., Albugo koreana, Albugo lepidii and Albugo voglmayrii. The comparative investigation of the effector genes and host targets in the generalist and the specialist species may constitute a model system for elucidating the fundamental processes involved in plant pathogen co-adaptation and speciation.
    Keywords: Albuginales ; effector gene ; oospore morphology ; phylogeny ; plant pathogen ; speciation
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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