Sudden oak death genome mapped

By: PAUL ELIAS - Associated Press | Thursday, June 10, 2004 9:42 PM PDT ∞

SAN FRANCISCO ---- Researchers announced Thursday that they have completed the genetic blueprint of the blight-causing culprit responsible for sudden oak death, a plant disease that is wiping out forests and hurting nurseries across the country and especially in California.

The $4 million effort funded by three federal agencies also produced the genetic sequence of a close cousin responsible for destroying millions of dollars' worth of soybeans each year.

The trick is to sift through the 15,000 genes of each funguslike pest in search of the one gene, or combination of a few genes, that make the one-cell microbes so deadly to plants.

The gene hunters hope they can find the bad genes by comparing the two genomes and investigating the similarities and differences between them.

"If we can figure that out and crack that code, we can develop tools to detect, prevent or cure the diseases," said Daniel Rokhsar of the Joint Genome Institute in Walnut Creek, where the two genomes were produced.

First discovered in Mill Valley in 1995, sudden oak death is now destroying forests in 13 California counties, hitting hardest in Marin, Santa Cruz, Monterey and Sonoma counties. The funguslike killer has also been found in 125 nurseries across the country.

In April, the federal government barred California nurseries from shipping 59 plant species out of state until they can be declared free of the disease. That declaration came after it was found in a San Marcos nursery that had purchased products from an Azusa nursery in Los Angeles County.

Sudden oak death has been found in 14 states, 13 of which are known to have received plants from a single nursery in California. At least 10 states have restricted the sale of plants targeted by the microbes, and Florida banned the import and sale of all nursery plants from California.

The resulting halt in sales was particularly harmful to North County nurseries who lost early spring and Mother's Day sales to other states. San Diego County has about 9,000 acres devoted to nursery and flower crops with a combined value of $855 million in 2001, according to county agricultural officials.

The blight, which is related to the type of organism believed to have caused the Irish potato famine in the mid-19th century, does not necessarily kill the trees and plants it infects, but no cure has been found and it's unclear how it spreads.

Katie Palmieri of the California Oak Mortality Task Force, which was created to combat the disease in the state, said there is evidence that the disease is spread via transportation of firewood, by hikers who pick it up on their shoes, and by rainwater splashing in the forest.

She said there is no known way to counteract the microbes, which are impervious to pesticides and other traditional pest-control methods.

"It's devastating when it occurs," Palmieri said.

Staff writer Mark Walker contributed to this report.

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