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An international test performance study (TPS) was organised to generate validation data for three molecular Synchytrium endobioticum tests: van den Boogert et al. (European Journal of Plant Pathology 113, 47-57, 2005), and van Gent-Pelzer et al. (European Journal of Plant Pathology, 126, 129-133, 2010) for the detection of S. endobioticum, and the pathotype 1(D1) identification test described by Bonants et al. (European Journal of Plant Pathology, 143, 495-506, 2015). Two TPS rounds were organised focussing on different test matrices, i.e. round 1: warted potato tissue, and round 2: resting spore suspensions. When using the tests for detection and identification of S. endobioticum in warted potato tissue, no significant differences were observed for diagnostic sensitivity, diagnostic specificity, overall accuracy, analytical sensitivity and robustness. When using the tests for detection and identification of S. endobioticum in resting spore suspensions, the van den Boogert and van Gent-Pelzer tests significantly outperform the Bonants test for diagnostic sensitivity and diagnostic specificity. For overall accuracy and analytical sensitivity, the van Gent-Pelzer significantly outperforms the van den Boogert and Bonants tests and is regarded as the test of choice when identifying S. endobioticum from resting spores. Tests regarded fit for purpose for routine testing of wart material and resting spore suspensions are proposed for the update of EPPO standard PM7/28(1) Synchytrium endobioticum. [ABSTRACT FROM AUTHOR]

The longevity, infectivity and virulence of winter sporangia of Synchytrium endobioticum, the causal agent of potato wart disease, were studied in soil collected from an infested plot 43 years since the last observed infection. The demarcated plot was located in a mountainous area of the central part of Sudetes Mountain range in Poland and no potatoes were grown in the plots over that period. Sporangia of S. endobioticum were collected from the samples and retained viability after 46 years. Infectivity of the fungus was tested using modified Potoček's tube test. The ability of the spores to invade and replicate in potato host tissue was demonstrated using sporangia collected after 43 years. The virulence of the obtained isolates was tested with the Glynne-Lemmerzal method. Two different pathotypes were identified: 1(D1), the most widely distributed in Europe and 3(M1), a unique Polish local pathotype, which was isolated and identified for the first time from the same location in 1965. [ABSTRACT FROM AUTHOR]

Synchytrium endobioticum is a severe pathogen of potato causing wart disease. For this obligate fungus many pathotypes exist, which are pathogenic or non-pathogenic to different cultivars of potato. To determine to which pathotype an isolate belongs, two biological assays are used on a set of different potato cultivars: the Spieckermann and the Glynne-Lemmerzahl test. A differential set of cultivars has been recommended by EPPO (European Plant Protection Organization) for these tests. Drawbacks of these tests are that it can take up to several months to score the interaction and results are difficult to score and also often not conclusive. Therefore, possibilities were investigated to look for molecular markers for pathotype specificity. An extremely low level of diversity was observed in a set of eight isolates using CRoPS™ (Complexity Reduction of Polymorphic Sequences) technology. Only 191 sequence polymorphisms were found in 14,660 contigs representing approximately 195 Kb of sequence for eight isolates. Nine sequence polymorphisms could be related to pathotype specificity. Two of these polymorphisms were transferred into a real-time TaqMan PCR assay to discriminate between pathotype specific groups. Validation of the assays was performed using multiple isolates from different countries for which the bioassay had been performed. [ABSTRACT FROM AUTHOR]

Lipid classes and fatty acid distribution were analysed in the resting sporangium of Synchytrium endobioticum, the causal agent of the potato wart disease. The sporangium contents were shown to have lipid droplets, the major fatty acids there being C, C, and C. The sporangium wall on the other hand was composed of C, C, C, C, and C fatty acids. A significantly large portion of the sporangium wall lipids contained wax esters with branched chains. [ABSTRACT FROM AUTHOR]

The cytoplasmic organization of the long-lived, thick walled resting stage of the sporangium of Synchytrium endobioticum (Schilb.) Perc. is described. The cytoplasm of the resting sporangium contains a large number of closely packed lipid bodies and irregular electron dense bodies, which are interspaced with fine channels of cytoplasm. These ultrastructural observations are discussed in relation to the hypothesis of Bally (1912) and Curtis (1921) that zoospore primordia are already present during the resting stage. It is shown that the 'zoospore primordium' is actually a lipid body and an osmiophilic body and the strands postulated to connect the individual 'zoospore primordia' are actually the fine channels of cytoplasm. A new inner wall layer is laid down prior to the start of the germination. It is this wall layer which will protrude to form the vesicle in which sporogenesis takes place. The germination process observed, protrusion of a vesicle through a crack in the sporangial wall, the migration of the sporangial content into the vesicle, and the formation of a single, membrane-bound sporangium within this vesicle, is in full agreement with the recent light microscopic studies of Sharma and Cammack (1976). These observations support the transfer of S. endobioticum from the subgenus Mesochytrium to the subgenus Microsynchytrium (both sensu Karling 1964). A major objective of the study, to obtain ultrastructural evidence for the location of the meiotic divisions in the life cycle, was not fulfilled. Three different fungi were observed to parasitize the resting sporangium of S. endobioticum. These infections are discussed in relation to other mycoparasites of plant pathogenic fungi. The possibility of using a mycoparasite for the biological control of potato wart disease is considered to be without practical relevance. [ABSTRACT FROM AUTHOR]

An ultrastructural study of the development of the resting sporangium of Synchytrium endobioticum (Schilb.) Perc. infecting potato cells is presented. The resting sporangium is found to have a single large, centrally placed nucleus with a prominent nucleolus through its entire in situ development. The cytoplasmic organization of the resting sporangium is further characterized by numerous membrane-bound lipid bodies and osmiophilic bodies. The latter have a characteristic sieve-like appearance, probably because certain storage components have been extracted during preparation for electron microscopy. Because of the similar location and appearance of these osmiophilic bodies it is suggested that they are identical to what has earlier (based on light microscopy) been described as chromatin granules; and the ultrastructural studies presented here show that 'nucleolar discharge' which was described from light microscopic observations as leading to chromatin granules in the cytoplasm, and finally forming the nuclei of the zoospores ( bally 1912, curtis 1921, percival 1910) simply does not occur. The appearance of dense fibrillar-like structures on the sporangial surface at an early stage of resting sporangium development ultrastructurally distinguishes the resting sporangium from the zoosporangium. The development of the layered portion of the thick sporangial wall is shown to be due to the fusion of vacuoles containing pre-made wall fibrils with the cell membrane. It is suggested that the inner compact wall layer which is essentially substructureless is formed by the membrane itself. The characteristic 'wings' of the mature S. endobioticum resting sporangium originate from the potato host cell wall. Remnants of host cell organelles in the outermost layer of the resting sporangium wall show that degradation of the host cell cytoplasm contributes to wall formation of the parasite. [ABSTRACT FROM AUTHOR]

An ultrastructural study of zoosporangium development of Synchytrium, endobioticum (Schilb.) Perc. is presented. Emphasis is placed on the location of the parasitic fungal thallus in the potato host cell, on the specific location of organelles in relation to the developing zoosporangial wall, and on the host cell reaction to the fungal infection. The cytoplasmic organization of the individual sporangia after division of the zoosporangium into a sorus of sporangia is characterized by numerous similarly sized nuclei, well developed dictyosomes, and the presence of many lipid bodies of variable size. Cytoplasmic microtubules are observed to flare out from the functional kinetosome both before and after zoospore cleavage. The ultrastructural details of zoosporangium development are used to revaluate the life cycle of S. endobioticum as described from light microscopic observations made early in the century ( Curtis 1921; Köhler 1923, 1932; Percival 1910). [ABSTRACT FROM AUTHOR]