RESEARCH ARTICLE Elevated Genetic Diversity in the Emerging Blueberry Pathogen Exobasidium maculosum

Emerging diseases caused by fungi are increasing at an alarming rate. Exobasidium leaf and fruit spot of blueberry, caused by the fungus Exobasidiummaculosum, is an emerg-ing disease that has rapidly increased in prevalence throughout the southeastern USA, severely reducing fruit quality in some plantings. The objectives of this study were to deter-mine the genetic diversity of E.maculosum in the southeastern USA to elucidate the basis of disease emergence and to investigate if populations of E.maculosum are structured by geography, host species, or tissue type. We sequenced three conserved loci from 82 iso-lates collected from leaves and fruit of rabbiteye blueberry (Vaccinium virgatum), highbush blueberry (V. corymbosum), and southern highbush blueberry (V. corymbosum hybrids) from commercial fields in Georgia and North Carolina, USA, and 6 isolates from lowbush blueberry (V. angustifolium) from Maine, USA, and Nova Scotia, Canada. Populations of E. maculosum from the southeastern USA and from lowbush blueberry in Maine and Nova Scotia are distinct, but do not represent unique species. No difference in genetic structure was detected between different host tissues or among different host species within th