Seasonal isolation and genomic comparison of Discula destructiva, the causal agent of dogwood anthracnose, and an undescribed Discula species

Forty-three isolates of D. destructiva and 28 isolates of an undescribed Discula sp. were collected from flowering dogwoods (Cornus Florida) from 13 sites in Alabama, Georgia, North Carolina, Tennessee, andVirginia during 2000 and 2001. Discula destructiva and Discula sp. were identified using size and shape of conidia and presence of internal fat bodies.The fungi were differentiated into D. destructiva and Discula sp. using gallicacid medium. In the spring and summer, 13 more isolates ofZ). destructive were obtained than Discula species. However, the frequency of isolatingDiscula sp. was higher than has been reported in previous studies. In the fall, D. destructiva was isolated once, and in the winter neither fungus was isolated. The ability to isolate fungi was not associated with aspect,proximity to water, elevation, and diameter breast height.Genetic analysis was performed comparing DNA of 16 isolates of Discula sp. and two isolates of Z. destructiva. DNA amplification fingerprinting (DAF) used five octomer primers that revealed polymorphisms were more common among isolates of Discula sp. thanisolates of D. destructiva. Similarities in groups of Discula sp. isolates were mostly within the same site. These findings indicate that Discula sp. and D.illdestructiva are most likely not the same species but are related fungi in the same family.