Mycologia, 87(4), 1995, pp. 490-500. ? 1995, by The New York Botanical Garden, Bronx, NY 10458-5126 DNA amplification fingerprinting provides evidence that Discula destructiva, the cause of dogwood anthracnose in North America, is an introduced pathogen Robert N. Trigiano Department of Ornamental Horticulture and Landscape Design, Institute of Agriculture, The University of Tennessee, Knoxville, Tennessee 37901-1071 Gustavo Caetano-Anolles Brant J. Bassam1 Plant Molecular Genetics, Institute of Agriculture and Center for Legume Research, The University of Tennessee, Knoxville, Tennessee 37901-1071 Mark T. Windham Department of Entomology and Plant Pathology, Institute of Agriculture, The University of Tennessee, Knoxville, Tennessee 37901-1071 Abstract: DNA amplification fingerprinting was used to characterize 28 isolates of Discula destructiva and three isolates of an undescribed species of Discula. These filamentous fungi cause anthracnose of various species of dogwood (Cornus). Isolates were obtained from throughout the disease range in the eastern and western United States and western Canada and DNA amplification fingerprinting profiles generated with 10 arbitrary oligonucleotide primers. Fifty-nine of 302 loci examined were polymorphic between isolates of D. destructiva, whereas a greater number were ob? served between and among the isolates of Discula spe? cies. Relationships among and between the two fungal groups were ascertained using cluster analysis and phylogenetic analysis using parsimony. DNA profiles resulting from pooled (equal amounts) DNA from five isolates of D. destructiva from the eastern United States were compared to profiles from bulked DNA from five and 10 isolates from western United States to discern differences between the two geographical pop? ulations. The genome of D. destructiva appears to be highly conserved throughout the range of the disease, whereas isolates of Discula species exhibited greater variability. Profiles of bulked DNA from eastern and western United States were identical indicating very few differences between the populations. The data suggest that D. destructiva was recently introduced into North America. Accepted for publication April 6, 1995. 1 Present address: Cooperative Research Centre for Tropical Plant Pathology, University of Queensland, Qld. 4072 Australia. Key Words: arbitrary primers, Cornus species, DAF, Discula destructiva, genomic analysis INTRODUCTION Anthracnose of flowering dogwood (Cornus florida L.), a native understory tree in the eastern deciduous for? est ofthe United States, was initially observed in south- eastern New York and southwestern Connecticut in 1978 and 1979 (Hibben and Daughtrey, 1988). Since then, the disease has spread rapidly through native populations in the Appalachian mountains and asso? ciated highland areas to northeastern Alabama. The consequences of the disease can be severe, often dec- imating populations as is the case in Catoctin Moun- tain Park in Maryland (Schneeberger and Jackson, 1989). A similar disease was also reported to occur on Pacific dogwood (C. nuttalli Aud.) in 1976 (Salogga and Ammirati, 1983) in the state of Washington and has since expanded to adjacent populations in western U.S. and Canada and to disjunct populations in Idaho. The sudden appearance and rapid dissemination of the disease on both the east and west coasts of North America has led to the hypothesis that the causal or? ganism is an introduced pathogen (Hibben and Daughtrey, 1988; Redlin, 1991; Daughtrey, 1994; Daughtrey and Hibben, 1994). The disease was initially ascribed to various fungal pathogens, but Koch's postulates were fulfilled re? cently using an undescribed species of Discula (Hibben and Daughtrey, 1988) which was subsequently char- acterized as D. destructiva Redlin (Redlin, 1991). An undescribed Discula species was also found associated with the disease. This organism is also considered to be a causal agent but was isolated from only 7 to 8% of disease specimens in a recent survey of symptomatic trees in Pennsylvania and Maryland (Windham, un? publ. data). Although Apiognomonia is the telomorph for a number of other species of Discula, the perfect stage has not been identified for either species in? cluded in this study. The two species of Discula can usually be distin- guished by growth habit on agar media and their ability to oxidize gallic acid (Trigiano et al., 1991). Although morphological and physiological attributes are used extensively in classifying fungal species, they assess phenotypic qualities that may be variable and subject 490 This content downloaded from 130.126.162.126 on Tue, 28 Jun 2016 16:37:29 UTC All use subject to http://about.jstor.org/terms