Submitted to: Mycologia
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/20/2002
Publication Date: 1/20/2003
Citation: PAULITZ, T.C., ADAMS, K.J., MAZZOLA, M. A NEW SPECIES FROM EASTERN WASHINGTON.. MYCOLOGIA. 95(1): 80-86. 2003. Interpretive Summary: A new species of Pythium was discovered in wheat fields in eastern Washington. This species was named Pythium abappressorium, based on its unusual appressoria, which are penetration structures formed by the fungus. P. abappressorium causes root rot and damping-off of wheat, but is not pathogenic to apples. The ITS region of the ribosomal DNA was sequenced, and did not match any Pythium species from a database of over 1200 Pythium isolates.
Technical Abstract: A new species of Pythium isolated from wheat and apple roots in eastern Washington is described. Pythium abappressorium sp. nov. is characterized by abundant appressoria. Plerotic oospores and sporangia are formed from the appressoria and remnants of the appressoria remain attached to the base of sporangia at maturity. Smaller appressorial swellings, reminiscent of hyphal swellings, are also formed within the appressoria. P. abappressorium is pathogenic to wheat, causing damping-off and stunting, but is not pathogenic to apples. The fungus can grow in the temperature range 5 to 30 C, with an optimum of 20 C. The sequence of the ITS1 region of the rDNA did not match the sequences from a worldwide collection of over 1200 isolates, including types and neotypes, suggesting that this species has not been previously described.