Development of Microsatellite Markers from Erysiphe pulchra (Dogwood Powdery Mildew) for Analyzing Genetic Diversity

Flowering dogwood (Cornus florida), and kousa dogwood (C. kousa) are economically significant ornamental plants in the nursery and landscape industry. Flowering dogwood has been severely affected by dogwood anthracnose (Discula destructiva) and powdery mildew (Erysiphe pulchra). Kousa dogwood is more tolerant than flowering dogwood to both diseases. Powdery mildew resistant flowering dogwood cultivars are available commercially. The life history of powdery mildew on dogwood has been investigated, however population structure and genetic diversity of E. pulchra is unexplored. Genome sequencing of the flowering dogwood powdery mildew fungus E. pulchra was used to develop microsatellite markers. A total of 6,163,317 sequences were assembled de novo into 118,161 contigs and 18 microsatellite loci were identified from 500 randomly selected contigs. Screening of these loci against four E. pulchra samples revealed that nine loci were suitable for further characterization. The nine loci were used to genotype total DNA isolated from 47 powdery mildew infected leaves from Maryland, Mississippi, New Jersey, and Tennessee. Fourteen alleles were detected, but only four lociloci were polymorphic and informative. Shannon’s information index was 0.12 and ranged from 0.00 to 0.45. Private alleles were detected in the Mississippi and Tennessee samples. Clustering of the samples using two dimensional principal coordinates analysis explained 65% of the variation and clustered independent of geographical location. This research demonstrates that genome sequencing of an obligate biotroph fungal pathogen is valuable for developing microsatellites for population studies of E. pulchra and the low genetic diversity indicates primarily asexual reproduction by the pathogen.