The fungus-like microorganism, Phytophthora ramorum, is the target of Agricultural Research Service (ARS) scientists working in laboratories and greenhouses on both coasts because it's best known for causing Sudden Oak Death disease in trees and plants, such as oak trees and woody backyard plants like azaleas and camellias.

P. ramorum has threatened California's scenic oak woodlands since the mid-1990s. More than a half-million otherwise ready-to-sell nursery plants have been destroyed to ensure they wouldn't spread the infection.

Agricultural inspectors and plant nursery operators checking their stock for the microbe might soon have additional help from a laboratory test developed by ARS plant pathologists Frank N. Martin at Salinas, Calif., and colleague Paul W. Tooley at Ft. Detrick, Md. Their assay is based on a stretch of mitochondrial DNA — telltale genetic material that occurs outside of a cell's nucleus, according to Tooley.

The assay may complement the tests of the pathogen's nuclear DNA that are already in use, Martin noted.

Fast, reliable assays help technicians in plant-health laboratories across the county determine if the microbe in plant samples they're examining is, or isn't, P. ramorum.

Martin, who's based in the ARS Crop Improvement and Protection Research Unit, and Tooley, in the agency's Foreign Disease-Weed Science Research Unit, developed the test with Cheryl L. Blomquist, a State of California plant pathologist.

For more of the article by Marcia Wood, visit

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