Differentiation of Isolates of Discula umbrinella (Teleomorph: Apiognomonia errabunda) from Beech, Chestnut, and Oak Using Randomly Amplified Polymorphic DNA Markers. U. A. Haemmerli. Institute of Plant Science, ETH Zentrum, CH-8092 Zürich, Switzerland. U. E. Brändle(1), O. Petrini(2), and J. M. McDermott(1). (1)Institute of Plant Science, ETH Zentrum, CH-8092 Zürich, Switzerland; (2)Microbiology Institute, ETH Zentrum, CH-8092 Zürich, Switzerland.. MPMI 5:479-483. Accepted 21 August 1992. Copyright 1992 The American Phytopathological Society.

Genetic variation in 30 isolates of Discula umbrinella derived from beech, chestnut, and oak was assessed using randomly amplified polymorphic DNA (RAPD) and restriction fragment length polymorphic markers. Polymerase chain reaction amplifications with 17 primers produced 134 different DNA fragments. Three RAPD fragments were subsequently used for Southern hybridization. By these techniques up to four different individuals could be detected in the same leaf. The presence of several individuals within a single leaf indicates a finely tuned balance between the endophyte and its host. Cluster analysis of all arbitrary primed amplified DNA fragments showed that the isolates could be placed into four groups corresponding to their host origin. The high percentage of private RAPD variants within groups is consistent with low gene flow.