Phytophthora stricta isolated from Rhododendron maximum in Pennsylvania

During a survey in October 2013 in the Michaux State Forest in Pennsylvania (Pennsylvania Department of Conservation and Natural Resources Permit number SFRA-1351), mature plants of Rhododendron maximum were noticed alongside a stream with nondescript necrotic lesions at the tips of some mature leaves that had been in contact with the stream water. Several leaves were collected and taken back to the laboratory for processing. Segments from 10 leaves were removed at the interface of the lesion area, surface-sterilized for 20 s in 70% ethanol and rinsed three times in sterile water. The segments were plated on PARPH+V8 Phytophthora selective medium (Ferguson and Jeffers, 1999). The plates were kept in the dark at 20oC. After approximately 3 d, colonies resembling a Phytophthora sp. were observed growing from the segments of two leaves. Mycelial tips were transferred to 20% V8 agar (isolates MSF-C and MSF-F). The isolates were identified as P. stricta based on sequences from the internal transcribed spacer (...