Data from: Confirmation of independent introductions of an exotic plant pathogen of Cornus species, Discula destructiva, on the east and west coasts of North America

Cornus florida (flowering dogwood) and C. nuttallii (Pacific dogwood) are
North American native tree species that belong to the big-bracted group of
dogwoods. Cornus species are highly valued for their ornamental
characteristics, and have fruits that contain high fat content for
animals. Also, they are an important understory tree in natural forests.
Dogwood anthracnose, caused by Discula destructiva, was observed in the
late 1970s on the east and west coasts of the United States and by 1991
had quickly spread throughout most of the native ranges of C. florida and
C. nuttalli. We investigated the genetic diversity and population
structure of 93 D. destructiva isolates using 47 microsatellite loci
developed from the sequenced genome of the type strain of D. destructiva.
Clone-corrected data indicated low genetic diversity and the presence of
four genetic clusters that corresponded to two major geographic areas, the
eastern United States and the Pacific Northwest, and to the two collection
time periods when the isolates were collected (pre- and post-1993).
Linkage disequilibrium was present in five out of six subpopulations,
suggesting that the fungus only reproduced asexually. Evidence of
population bottlenecks was indicated across four identified genetic
clusters, and was probably the result of the limited number of founding
individuals on both coasts. These results support the hypothesis that D.
destructiva is an exotic pathogen with independent introductions on the
east and west coasts of North America. We also tested the
cross-amplification of these microsatellite primers to other Discula
species. Genomic DNA from 17 isolates of four other Discula species and
two isolates of Juglanconis species (formerly Melanconis species) were
amplified by 17 of 47 primer pairs. These primers may be useful for
investigating the genetic diversity and population structure of these
Discula species.