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Two new species of Pythium, P. senticosum and P. takayamanum, isolated from cool-temperate forest soil in Japan

     River Basin Research Center, Gifu University, Gifu 501-1193, Japan

Haruhisa Suga

     Life Science Research Center, Gifu University, Gifu 501-1193, Japan

C. André Lévesque

     Eastern Cereal and Oilseed Research Center, Agriculture and Agri-Food Canada, 960 Carling Avenue, Ottawa, ON K1A 0C6 Canada

Pythium senticosum and P. takayamanum spp. nov. were isolated from cool-temperate forest soil in Japan. P. senticosum can grow at 5 C and is fast growing at 25 C with a radial growth of 22.2 mm 24 h^–1. The species is morphologically characterized by ovoid to ellipsoid sporangia with apical papilla, ornamented oogonia with acute conical spines, and antheridia with broad attachment to oogonia. P. takayamanum is very different and can grow at 35 C. This species is morphologically characterized by its wavy antheridial stalks and ellipsoidal oogonia with constricted areas. Phylogenetic analyses of the ITS rDNA region and the partial COX2 gene showed that the two species are genetically distinct from each other and from their closest relatives. P. senticosum is closely related to P. dimorphum and P. undulatum whereas P. takayamanum is closely related to P. rhizosaccharum and P. parvum.

Key words: COX2 gene, ITS rDNA region, oomycete, phylogeny, taxonomy