title: Intra-isolate heterogeneity of the ITS region of rDNA in Pythium helicoides.
abstract: Heterogeneity of the rDNA ITS region in Pythium helicoides and the phylogenetic relationship between P. helicoides and closely related species were investigated. In PCR-RFLP analysis of the rDNA ITS region of six P. helicoides isolates investigated, including the type culture, intraspecific variation was found at the HhaI site. The total length of fragments was longer than before cutting, indicating sequence heterogeneity within isolates. Digestion of the cloned rDNA ITS region derived from seven isolates with HhaI revealed polymorphisms among and within single zoospore isolates, and variability of the region was also present among the clones derived from the same isolate. To test whether the rDNA ITS region of closely related species and other regions in the genome of P. helicoides are also variable, the rDNA ITS region of P. ultimum and the cytochrome oxydase II (cox II) gene encoded in mitochondria were sequenced. P. ultimum had little variation in the rDNA ITS region. The cox II gene sequences of both species revealed only a low intraspecific variability and no intra-isolate variation. In the phylogenic tree based on the rDNA ITS sequences, all clones of P. helicoides formed one large clade that was distinct from the clades comprising morphologically similar species, such as P. oedochilum and P. ostracodes, and was closely related to P. chamaehyphon rather than the other species.
authors.affiliation: River Basin Research Center, Gifu University, Gifu 501-1193, Japan. kageyama@green.gifu-u.ac.jp
authors.forename: Koji
authors.initials: K
authors.lastname: Kageyama
authors.forename: Masako
authors.initials: M
authors.lastname: Senda
authors.forename: Takahiro
authors.initials: T
authors.lastname: Asano
authors.forename: Haruhisa
authors.initials: H
authors.lastname: Suga
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Ishiguro
mesh_terms: D004271:DNA, Fungal / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D003576:Electron Transport Complex IV / Q000235:genetics; D005800:Genes, Fungal; D014644:Genetic Variation; D010802:Phylogeny; D010935:Plant Diseases / Q000382:microbiology; D018517:Plant Roots / Q000382:microbiology; D012150:Polymorphism, Restriction Fragment Length; D011775:Pythium / Q000235:genetics*; D017422:Sequence Analysis, DNA
chemical_list: D004271:DNA, Fungal; D004275:DNA, Ribosomal; D021903:DNA, Ribosomal Spacer; D003576:Electron Transport Complex IV