Desiccation at Ambient Temperature Effectively Preserves Plant Tissues Infected with Phytophthoras

Abstract

Conventionally, plant samples collected in the course of field surveys for Phytophthora spp. (e.g., in the context of the US Forest Service-sponsored national P. ramorum survey of forest environments) are either processed immediately or stored at low temperatures and processed as soon as possible for detection by molecular methods. In order to extend the useful life of the sample, a method involving tissue desiccation was explored for effectively storing Phytophthora-infected plant leaves. In one experiment, rhododendron leaves inoculated with an unknown Phytophthora sp. and desiccated for seven days yielded DNA of sufficient quality for species identification via sequencing of the ITS region. In a second experiment, P. ramorum was successfully detected by PCR in inoculated leaves of California bay laurel, California buckeye, bigleaf maple, rhododendron, and viburnum that were desiccated and stored at room temperature for four months. Therefore, desiccation might be a viable, reliable, and less expensive alternative to storing foliar samples at low temperature. Accepted for publication 11 November 2006. Published 2 March 2007.