title: Distinguishing homokaryons and heterokaryons in Phellinus sulphurascens using pairing tests and ITS polymorphisms.
abstract: Phellinus sulphurascens Pilát causes laminated root rot of coniferous species in both western North America (WNA) and Asia. Accurate somatic incompatibility tests for mapping population structures have been difficult to conduct for P. sulphurascens because no single, unambiguous criterion has allowed differentiation of homokaryotic and heterokaryotic isolates. In a population study of P. sulphurascens in WNA, two types of ITS sequences were found in the single spore and vegetative isolates. All single spore isolates (SSIs) had either ITS type-1 or type-2 whereas some vegetative isolates had both ITS types. The segregation pattern for inheritance of ITS, which we observed in SSIs from eight basidiocarps, suggested that each ITS type occurred in a different nucleus and that each basidiospore inherited only one ITS type. In four SSIs from Russia and eight heterokaryotic isolates from Japan, nine different ITS types, referred to as type-3 to -11, were detected. A variety of pairing tests conducted between known Asian and WNA homokaryon and heterokaryon isolates did not always give consistent results with respect to fungal mat morphologies and formation of demarcation lines. However, the ITS types that occurred after pairing tests did follow consistent patterns. Thus, using ITS polymorphisms and pairing tests between Asian tester isolates and 49 vegetative isolates from WNA, we were able to accurately distinguish between homokaryotic and heterokaryotic isolates.
authors.affiliation: Institute of Molecular Biology and Genetics, Seoul National University, 56-1 Shillim-dong, Kwanak-gu, Seoul, 151-742, Korea. ywlim@snu.ac.kr
authors.forename: Young Woon
authors.initials: YW
authors.lastname: Lim
authors.forename: Rona
authors.initials: R
authors.lastname: Sturrock
authors.forename: Isabel
authors.initials: I
authors.lastname: Leal
authors.forename: Kevin
authors.initials: K
authors.lastname: Pellow
authors.forename: Takehiro
authors.initials: T
authors.lastname: Yamaguchi
authors.forename: Colette
authors.initials: C
authors.lastname: Breuil
mesh_terms: D001208:Asia; D001483:Base Sequence; D001487:Basidiomycota / Q000235:genetics* / Q000254:growth & development; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics*; D021903:DNA, Ribosomal Spacer / Q000235:genetics*; D009656:North America; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D012150:Polymorphism, Restriction Fragment Length; D017422:Sequence Analysis, DNA
chemical_list: D004271:DNA, Fungal; D021903:DNA, Ribosomal Spacer