Summary of topics offered - Faculty of Forestry and Wood Technology

Basic information

Type of work:
Dissertation thesis
Topic: Investigations of the lifestyle, the ecological role and the breeding system of the new oomycete genus Nothophytophthora
State of topic:
approved (prof. Dr. Ing. Libor Jankovský - head of department)
Thesis supervisor: Dr. Thomas Jung
Faculty of Forestry and Wood Technology
Supervising department:
Department of Forest Protection and Wildlife Management - FFWT
Max. no. of students:
Proposed by:
Dr. Thomas Jung
During various recent surveys of Phytophthora diversity in Germany, Portugal, Chile and Vietnam slow growing oomycete isolates were obtained from rhizosphere soil samples and small streams in natural and planted forest stands. Multigene phylogenetic analyses revealed they belong to six new species of a new genus, Nothophytophthora gen. nov., which constitutes a monophyletic sister group to Phytophthora. Undescribed Nothophytophthora species have since been detected also in Czech Republic, Slovakia, Norway, Scotland, Spain, Sweden, New Zealand, Japan and the USA. Nothophytophthora species share numerous morphological characters with Phytophthora and can be differentiated from the latter by the presence of a conspicuous, opaque plug inside the sporangiophore close to the base of most mature sporangia and intraspecific co-occurrence of sporangial caducity and nonpapillate sporangia with internal nested and extended proliferation in several Nothophytophthora species. The lifestyle of Nothophytophthora species is still unknown. Their widespread occurrence in watercourses suggests a saprophytic lifestyle as decomposers of leaf litter. However, production of caducous sporangia by N. caduca, N. chlamydospora and N. valdiviana from Valdivian rainforests and N. vietnamensis from a mountain forest in Vietnam suggests a partially aerial lifestyle as adaptation to these humid habitats potentially as leaf pathogens. Three of the described Nothophytophthora species are homothallic while the other 3 described species are selfsterile. It is unknown whether the latter are fully sterile or whether in Nothophytophthora, like in Phytophthora, heterothallism exists. Objectives of the proposed PhD thesis are: O1. Morphology, physiology and phylogenetic position of new Nothophytophthora species: Morphological and physiological investigations of representative isolates of yet undescribed Nothophytophthora species from the culture collections of the Phytophthora Research Centre of Mendel University in Brno and of cooperating partners will be performed for their official scientific description. In addition, multigene phylogenetic analyses will be performed to clarify their phylogenetic position and refine the phylogeny of the genus Nothophytophthora. O2. Investigations into the lifestyle and ecological role of Nothophytophthora spp.: This will include extensive host range testing of available Nothophytophthora species using representative plant species from their native habitats and different pathogenicity testing methods (soil infestation tests, underbark inoculation tests, leaf inoculation tests). The ability of Nothophytophthora spp. to spread aerially via caducous sporangia and infect above-ground plant tissues will be tested under standardized conditions. In addition, sequence analyses will clarify whether and which Nothophytophthora spp. have elicitin genes and other genes associated with pathogenicity. Leaf decomposition trials will be performed using detached leaves from plant species dominant in their native habitats to assess the saprotrophic ability of Nothophytophthora spp. O3. Investigations of the breeding system of Nothophytophthora: Extensive mating tests of selfsterile Nothophytophthora species will be performed under different temperature conditions in agar and in situ in infected leaves using A1 tester strains of Phytophthora species from different phylogenetic clades and isolates from other selfsterile Nothophytophthora species. In addition, sequence analyses will be performed with all available homothallic and selfsterile Nothophytophthora species to clarify whether they have mating type genes recently found in the sister genus Phytophthora.

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D-FPM Forest Pathology and Mycology