Within a framework of task WP1.1 ‘Ecological approach to forest pest management’, there was a visit of dr Tomasz Oszako in University of Applied Science in Lullier, Switzerland, in order to exchange isolates taken from the soil samples with the use of baiting techniques. Thanks to such co-operation, both isolates and soil samples from Polish forest stands have been analyzed at the University in Lullier and then the results of sequencing have appeared in Genbank.
In a survey of oomycete species associated with forest decline in Poland numerous Pythium isolates have been collected. Since no reports about the implication of Pythium spp. in such decline have been reported, all these isolates, have been characterized with ITS rDNA sequences and with classical morphological descriptors for Pythium spp.. In addition to classical Pythium species currently recovered from soil such as Pythium ultimum var sporangiiferum and Pythium intermedium. three sets of isolates showed unique ITS sequences, different enough from those of any described species to justify new species status. The common paper describes and illustrates the morphology of these species and presents their taxonomic position and relationships with other related Pythium species belonging to the same clade. Pathogenicity of these isolates towards Quercus spp. have also been investigated and showed that some isolates were as aggressive as Phytophthora cinnamomi. The possible implication of Pythium species in the classical oak decline phenomenon is discussed based on current recovery of these pathogens from the sites investigated and pathogenicity tests.

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