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United States Department of Agriculture

Agricultural Research Service

Research Project: BIOLOGY AND EPIDEMIOLOGY OF EMERGING PLANT PATHOGENIC OOMYCETES

Location: Foreign Disease-Weed Science

Title: Long-term survival of Phytophthora kernoviae oospores

Author
item Widmer, Timothy

Submitted to: IUFRO Rusts of Pines Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: November 12, 2009
Publication Date: N/A

Technical Abstract: Phytophthora kernoviae is a pathogen recently found in the UK and New Zealand. To date, P. kernoviae is not known in the USA, but there is interest in studying this species and to prevent its entrance and establishment. Phytophthora kernoviae, not known to produce chlamydospores, is homothallic and produces abundant oospores. Therefore, the propagule most likely involved in long distance dispersal will be the oospore, making it important to study its biology. This study was conducted to examine long-term survival of oospores buried in sand at different temperatures. Oospores of one P. kernoviae isolate from the UK and one from New Zealand were imbedded separately onto 20 micrometer-mesh screens, buried in moist, autoclaved sand, and incubated at 4, 10, 20, or 30 degrees C. Over time, four screens were removed from each replication. The pathogenicity potential was checked by placing three screens on Rhododendron leaf disks. The remaining screen was exposed to 1 percent MTT, staining the oospores for viability. After 1 year, viability of the oospores was 82, 81, 79, and 58 percent for the UK isolate and 86, 75, 82, and 78 percent for the New Zealand isolate for the 4, 10, 20, and 30 degrees C treatments, respectively. No necrosis was observed on leaf disks exposed to oospores after 1 year at 30 degrees C. However, necrosis was observed at the other temperatures after being buried for 1 year. This demonstrates that P. kernoviae oospores can persist in sand for long periods of time at different temperatures and could be significant in spread of this pathogen.

Last Modified: 8/31/2014
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