DNA HYBRIDIZATION AND POLYMERASE CHAIN-REACTION (PCR) TESTS FOR IDENTIFICATION OF GAEUMANNOMYCES, PHIALOPHORA AND MAGNAPORTHE ISOLATES

DNA hybridization and PCR tests for Gaeumannomyces graminis and related fungi were developed to aid in their identification and classification. Hybridizations with a Gaeumannomyces graminis var. tritici mitochondrial DNA probe to restriction fragments from other Gaeumannomyces, Phialophora or Magnaporthe isolates demonstrated that almost all of the tested Gaeumannomyces and Phialophora isolates, including Gaeumannomyces cylindrosporus and Gaeumannomyces incrustans, had sequences homologous to the probe. In addition, M. poae had strong homology with the probe. Most isolates of Gaeumannomyces graminis var. tritici, the causative agent of take-all disease of cereals, had identical EcoR I and Msp I hybridization patterns, whereas sizes of hybridizing restriction fragments of Phialophora and Magnaporthe isolates showed more variation. Polymerase chain reaction (PCR) tests with primers developed for G. graminis var. tritici were positive for all G. graminis isolates. PCR tests for G. incrustans, G. cylindrosporus, Phialophora and Magnaporthe were positive, but test conditions in which positive results were obtained were more limited than PCR conditions which amplified G. graminis DNA.