title: Phylogenetic relationships of Pythium and Phytophthora species based on ITS rDNA, cytochrome oxidase II and beta-tubulin gene sequences.
abstract: Fifty-eight isolates representing 39 Pythium species and 17 isolates representing nine Phytophthora species were chosen to investigate intra- and intergeneric relationships with sequence analysis of three genomic areas. The internal transcribed spacer regions (ITS1 and ITS2), including the 5.8S gene of the ribosomal DNA were PCR amplified with the universal primers ITS1 and ITS4. On the other hand 563 bp of the cytochrome oxidase II (cox II) gene was amplified with the primer pair FM66 and FM58 for Pythium and FM75 and FM78 for Phytophthora. The 658 bp partial beta-tubulin gene was amplified with the forward primer BT5 and reverse primer BT6. Maximum parsimony analysis of the three DNA regions revealed four major clades, reflective of sporangial morphology. Clade 1 was composed of Pythium isolates that bear filamentous to lobulate sporangia. Clade 2 represents Pythium isolates that bear globose to spherical zoosporangia or spherical hyphal swellings. Meanwhile Phytophthora isolates were lumped into Clade 3 wherein the papillate, semipapillate and nonpapillate species occupied separate subclades. Lastly, Clade 4 was composed of Pythium species that bear subglobose sporangia resembling the papillate sporangia observed in Phytophthora. Hence a number of species (Ph. undulata, P. helicoides, P. ostracodes, P. oedochilum and P. vexans) have been proposed to be the elusive intermediate species in the Pythium-to-Phytophthora evolutionary line.
authors.affiliation: Genetics and Molecular Biology Division, Institute of Biological Sciences, University of the Philippines Los Baños, College, Laguna, Philippines.
authors.forename: Neilyn O
authors.initials: NO
authors.lastname: Villa
authors.forename: Koji
authors.initials: K
authors.lastname: Kageyama
authors.forename: Takahiro
authors.initials: T
authors.lastname: Asano
authors.forename: Haruhisa
authors.initials: H
authors.lastname: Suga
mesh_terms: D004271:DNA, Fungal / Q000032:analysis / Q000302:isolation & purification; D021903:DNA, Ribosomal Spacer / Q000032:analysis / Q000235:genetics*; D003576:Electron Transport Complex IV / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D010838:Phytophthora / Q000145:classification* / Q000201:enzymology / Q000235:genetics; D010935:Plant Diseases / Q000382:microbiology; D011775:Pythium / Q000145:classification* / Q000201:enzymology / Q000235:genetics; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D014404:Tubulin / Q000235:genetics*
chemical_list: D004271:DNA, Fungal; D021903:DNA, Ribosomal Spacer; D014404:Tubulin; D003576:Electron Transport Complex IV