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New pythium species isolated in Ohio

May 8, 2009  By Candace Pollock Ohio State University

May 7, 2009, Wooster, OH – A new species of Pythium, a water mould that
attacks crops in saturated soils, has been identified in Ohio.

May 7, 2009, Wooster, OH – A new species of Pythium, a water mould that attacks crops in saturated soils, has been identified in Ohio.

Anne Dorrance, an Ohio State University plant pathologist with the Ohio Agricultural Research and Development Center, said Pythium delawarii was labeled as a new species when its characteristics didn’t match any of the more than 200 described Pythium species.


The research was published in the March/April issue of the journal Mycologia.

“To identify a new species is an interesting process because Pythium species have different shapes,” said Dorrance. “Their mycelium takes on a different shape and their fruiting structures can be different from one species to another. This new species didn't fit any of the known Pythium descriptions. The final evidence was the DNA sequencing, which didn’t match any of the described species. It was proof that we indeed did have something that wasn't in any of the data banks.”

Pythium pathogens are water moulds that attack a number of crops via the plant roots in saturated soil conditions. They are one of the major causes of crop replants, and are becoming more economically important because of the continued rise in seed costs.

“What used to not be as big of an issue far as crop management decisions is becoming a bigger issue. Seed is a huge input for producers and a huge input for companies to produce it. With seed costs continuing to increase, producers can’t afford to be replanting their crop due to disease issues,” said Dorrance.

The new Pythium species was isolated from an Ohio field that experienced persistent stand establishment problems. So far the new species has been identified in a small number of locations across the state and doesn’t appear to be very aggressive.

“This isn’t a super aggressive species. The extent of its infection was forming lesions on the roots,” said Dorrance. “But it is an unusual species in that it thrives in warmer temperatures later in the season on older plants. People tend to identify Pythium mostly as a disease that thrives in cold soils in the spring on younger plants. There is such a broad range of species out there that it's unwise to use one label for all species. Never make a rule because there will be something in biology that will break it.”

Dorrance said the discovery would aid in future management of Pythium diseases and help in the breeding of new cultivars for resistance and new chemistries for seed treatment compounds.

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