Virginia Tech researcher advances fight against sudden oak death disease

Virginia Bioinformatics researcher Brett Tyler and his colleagues are one step closer to controlling a disease affecting California oak trees that is now showing up in nurseries in a dozen states, including Virginia, and threatening woody ornamentals and East Coast forests.

Tyler, a research professor at Virginia Bioinformatics Institute at Virginia Tech, and his colleagues have successfully mapped the genome of the devastating pathogens Phytophtora sojae and Phytophtora ramorum. P. ramorum, also known as sudden oak death, is a serious fungal pathogen that has attacked and killed tens of thousands of California and Oregon oak trees. P. sojae, the sister pathogen to P. ramorum, causes serious damage to soybean crops and cost growers $1 billion worldwide last year. These genome sequences will have great value in combating these devastating diseases.

The sequencing of P. sojae will serve as a "Rosetta Stone" to help researchers better understand P. ramorum's genome makeup and uncover valuable information to help control and prevent sudden oak death disease. In addition, the sequencing of the P. ramorum genome represents the fastest tracking time between the identification of a complex pathogen (in 2000) and the completion of its genome (in 2004).

Tyler, along with representatives from the U.S. Department of Energy Joint Genome Institute (JGI), U.S. Department of Agriculture (USDA), USDA Forest Service, the National Science Foundation (NSF) ), Affymetrix, and others will present the scientific findings to the media today at the Joint Genome Institute in Walnut Creek, Calif.

Sudden oak death disease has the potential to affect forests in the Appalachian highlands in Virginia and other areas on the East Coast. The disease kills the oak tree, but usually, the carrier shrubs survive. Sudden oak death has affected California redwood seedlings and sprouts but not the trunks. However, it poses a large threat to Virginia oak trees and other Eastern Seaboard plant species that have proven highly susceptible to the pathogen in greenhouse tests. Tyler identified the Virginia highlands as a potential target for P. ramorum, as they have the cool, moist air needed for spore spread and survival.

"Sudden oak death thrives in cool and moist West Coast forests," Tyler said. "Because 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 the $3.8 million project, which was funded by USDA, NSF, and DOE, to sequence all genes in P. sojae and P. ramorum.

Established in 2000 as a Commonwealth of Virginia shared resource, the Virginia Bioinformatics Institute (VBI) at Virginia Tech has a research platform centered on understanding the "disease triangle" of host-pathogen-environment interactions. With almost $30 million in research funding, VBI researchers are working to cure many human, crop, and animal diseases; create high-yield, insect- and disease-resistant crops; and provide bioinformatics information and tools to support further discoveries.

Founded in 1872 as a land-grant college, Virginia Tech has grown to become the largest university in the Commonwealth of Virginia. Today, Virginia Tech's eight colleges are dedicated to putting knowledge to work through teaching, research, and outreach activities and to fulfilling its vision to be among the top 30 research universities in the nation. At its 2,600-acre main campus located in Blacksburg and other campus centers in Northern Virginia, Southwest Virginia, Hampton Roads, Richmond, and Roanoke, Virginia Tech enrolls more than 28,000 full- and part-time undergraduate and graduate students from all 50 states and more than 100 countries in 180 academic degree programs.