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Preservation of genotypic diversity of a fungal pathogen within woody cankers

Madeline Dowling: Clemson University

<div><em>Monilinia spp.</em> cause brown rot, blossom blight, and twig cankers on stone fruits worldwide. Cankers are often overlooked as inoculum sources by orchard management strategies, though they may cause infections that remain quiescent until fruit maturity. In this study, we examined blossoms and cankers as diversity storage structures, seeing if multiple genotypes of <em>Monilinia fructicola </em>could infect blossoms and be transmitted to cankers. Fungal spores from blossoms and subsequent cankers were collected from 2 orchards in 2015 and 2016. Simple sequence repeat markers were used to genotype 10-20 single spores from four blossom/canker pairs per orchard. Single samples contained up to 5 genotypes, and the average genotype numbers in blossoms and cankers were not significantly different for both years (<em>p=</em>0.49, <em>p=</em>0<em>.</em>86) or farms (<em>p=</em>0.66, <em>p=</em>0.27), showing that a bottleneck effect did not occur during the transition from blossom to canker. The average number of genotypes unique to blossom or canker was also not significantly different in either year (<em>p=</em>0.12, <em>p=</em>0.87) or farm (<em>p=</em>0.73, <em>p=</em>0.27). In conclusion, a single blossom may be infected by 1 or more genotypes of <em>M. fructicola,</em> and the canker can store this diversity within a season. This information implicates <em>M. fructicola</em> cankers as diversity storehouses. We also found that multiple <em>B. cinerea </em>genotypes may infect a blossom, implying that these results may apply to other fungal diseases initiating in reproductive tissue.</div>