Population Structure and Reproductive Biology of Monilinia vaccinii-corymbosi in Vaccinium angustifolium in Maine.

The fungus Monilinia vaccinii-corymbosi (Mvc) causes mummy berry disease in blueberries including lowbush blueberry, Vaccinium angustifolium , and is a significant pathogen of concern for Maine lowbush blueberry growers. This disease is typically managed with fungicides or by burning of plant debris containing overwintering pseudosclerotia. The population structure of Mvc in various fields in Maine was investigated using microsatellites and isolates collected from three stages in the Mvc lifecycle. The impacts of management strategies were also examined. A high level of genetic diversity was observed in Mvc from twelve lowbush blueberry fields with 199 unique multilocus haplotypes (MLH) occurring in an original sample of 232 isolates. Twelve private alleles, including six private alleles with frequencies above 0.05, which indicated gene flow, were observed in six out of twelve fields. The population of Mvc in Maine as a whole is mostly a sexual, outcrossing population, as was seen in the diversity of MLH and low amounts of linkage disequilibrium, although some apothecia appear to result from selfing. Three fields appear to have some clonal reproduction, but were not strictly clonal, as multiple MLHs were noted in these fields. Management does not appear to affect population structure, and Mvc may be one large statewide population in Maine.