Fine-scale genetic structuring and reproductive biology of the blueberry pathogen Monilinia vaccinii-corymbosi
K. M. BURCHHARDT (1), M. A. Cubeta (1). (1) North Carolina State University, Raleigh, NC, U.S.A.
Mummy berry disease of blueberry (<i>Vaccinium</i> spp.) is caused by the economically important pathogen <i>Monilinia vaccinii-corymbosi</i> (Mvc). The fungus causes shoot infection followed by fruit infection through the gynoecial pathway. In this study, nine microsatellite markers were used to 1) examine fine-scale genetic structuring and gene flow; 2) compare the allele frequencies and genetic diversity of Mvc isolates that originated from infected shoots and fruit; and 3) determine if Mvc exhibits signatures of outcrossing and/or selfing. A collection of 269 isolates of Mvc was generated by sampling infected shoots and fruit from a 110 m x 134 m planting of southern highbush (<i>V. corymbosum</i> x <i>V. darrowii</i>). Genetic diversity was high, with 219 unique haplotypes detected. Spatial autocorrelation analysis did not support genetic structuring within the field, suggesting unrestricted gene flow at the sampled spatial scale. Analysis of molecular variance and Shannon partition analysis suggested that samples from shoots and fruit were not significantly different (P=0.196 and P=0.057, respectively). Analysis of single ascospore progeny indicated that five individual apothecia produced multiple recombinant ascospores, while two apothecia produced ascospores with identical haplotypes. These results suggest that Mvc can outcross, but may also be able to self-fertilize. Further research is needed to determine the scale at which genetic structuring occurs and the mating system of Mvc.
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