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Pythium Taxonomy

Pythium taxonomy is in a state of flux as molecular analyses reveal new relationships or confirm old ones. Many new species have been described that are of questionable validity. Changes in genus designations are being considered. A new genus has been proposed, Phytopythium, that would encompass members of the Pythium vexans complex (De Cock, A. W., G. P. Robideau, K. Bala, M. D. Coffey, Z. G. Abad and C. A. Levesque. 2010. Pythium, Pythiogeton and prov. name Phytopythium: The current status for the species in the genera. Phytopathology 100(6): S150-S150.) . S. Uzuhashi, M. Tojo, and M. Kakishima (16) have proposed splitting Pythium into four genera, based primarily on sporangium morphology, Ovatisporangium, Globisporangium, Elongisporangium, and Pilasporangium. Diagnosticians need to be aware that a name may change. The biology, host range, etc., do not change. Also, there are many opinions held by various experts as to whether a given 'species' has a great deal of diversity or is actually an artificial grouping of several species. Pythium irregulare is an example of this. Some scientists feel that the species is very diverse in its morphology while others believe that it should be split into Pythium irregulare, P. cylindorsporium, P. cryptoirregulare, and P. regulare. ("What's in a name? That which we call a rose, by any other name would smell as sweet." Juliet in Act II Scene II; Romeo and Juliet by William Shakespeare).