Magnetic resonance imaging (MRI) of oak trees infected with Phytophthora ramorum to determine potential avenues of infection in bark

Abstract

Non-destructive magnetic resonance imaging (MRI) revealed pathological anatomical features of coast live oak trees (Quercus agrifolia) that were naturally infected with Phytophthora ramorum. Fresh excised whole slices showing typical macroscopic cankers and bleeding were examined. Infected areas (i.e. cankers) were compared to presumed healthy sections. Various infected tissues were revealed and the depth of infection into the xylem could be estimated. Discontinuous distribution of water in the outer layer of sapwood was observed and high water concentrations appeared in the cankers. MRI also revealed channels in the periderm (bark) with high water concentration. Microscopic examination revealed the channels to be rays continuous with the rays extending into the xylem. The rays function in the radial conduction of water, and it is suggested that they may serve as an avenue of infection for P. ramorum.

Parent Publication

• Proceedings of the sudden oak death second science symposium: the state of our knowledge

Citation

Florance, Edwin R. 2006. Magnetic resonance imaging (MRI) of oak trees infected with Phytophthora ramorum to determine potential avenues of infection in bark. In: Frankel, Susan J.; Shea, Patrick J.; and Haverty, Michael I., tech. coords. Proceedings of the sudden oak death second science symposium: the state of our knowledge. Gen. Tech. Rep. PSW-GTR-196. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture: 91-99