"Sudden oak death thrives in cool and moist West Coast forests," said Tyler. "Since some Virginia forests and the Appalachian highlands have similar climates, they are in danger of being invaded by the pathogen."
According to Tyler, P. ramorum kills leaves on under-story shrubbery below the oaks, such as Virginia-native rhododendron, California bay laurel, azalea and camellia. Then spore-infected leaves fall to the ground while the shrub remains living and vibrant. From the ground, the leaf's P. ramorum spores are either blown by wind or splashed by rain to the oak's trunk where the pathogen infects the living bark layer. The P. ramorum infection spreads around the trunk's circumference and cuts off food supplies coming to the roots from the leaves, eventually killing the roots. Thus, the tree's death begins with the roots, causing the upper tree trunk, bark, limbs and leaves to die from lack of water.
The genome sequence of P. ramorum will help researchers develop better detection methods for sudden oak death, more accurately track the spreading of the disease, detect the routes of the spread, and determine if it can spread from nursery plants into the forest.
The USDA has identified ornamental shrubs imported from California infected with the disease in Virginia-based nurseries, as well as nurseries in 11 other states. As a result a nationwide quarantine has been placed on all imported shrubs from California.
In 2002, VBI in collaboration with the DOE Joint Genome Institute began this $3.8 million project, which was funded by USDA, NSF, and DOE, to sequence all genes in P. Sojae and P. ramorum.