HomePlant DiseaseVol. 99, No. 8First Report of Penicillium expansum Isolates With Reduced Sensitivity to Fludioxonil From a Commercial Packinghouse in Pennsylvania PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Penicillium expansum Isolates With Reduced Sensitivity to Fludioxonil From a Commercial Packinghouse in PennsylvaniaV. L. Gaskins, I. Vico, J. Yu, and W. M. Jurick IIV. L. GaskinsSearch for more papers by this author, I. VicoSearch for more papers by this author, J. YuSearch for more papers by this author, and W. M. Jurick IISearch for more papers by this authorAffiliationsAuthors and Affiliations V. L. Gaskins , Food Quality Laboratory, USDA-ARS, Beltsville, MD I. Vico , Department of Phytomedicine, University of Belgrade, Serbia J. Yu W. M. Jurick II , Food Quality Laboratory, USDA-ARS, Beltsville, MD Published Online:23 Jun 2015https://doi.org/10.1094/PDIS-11-14-1161-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Blue mold, caused by Penicillium expansum, is among the most economically significant disease of stored apples worldwide (Li and Xiao 2008). All commercial apples are susceptible to blue mold, leaving producers to rely on cultural practices and fungicides for control. Scholar (Syngenta Crop Protection, Greensboro, NC) was registered for control of Penicillium spp. on pome fruits. Scholar is a protectant, contact postharvest fungicide (active ingredient, fludioxonil). In February 2012, water samples were obtained from a presizing flume at a commercial facility in Pennsylvania with five isolates identified as P. expansum according to Pitt (2002). Conidial suspensions from each isolate were grown in triplicate on potato dextrose agar amended with 0.5 μg/ml technical grade fludioxonil and repeated according to Li and Xiao (2008). Four isolates with reduced sensitivity (R) grew, while one sensitive (S) isolate did not. Species-level identity was conducted for a representative R and S isolate via genomic DNA extraction followed by conventional PCR using β-tubulin specific primers according to Sholberg et al. (2005). MegaBLAST analysis of the 2× consensus amplicon sequences for the S isolate was 100% identical to P. expansum GenBank accession FJ012853.1 (E value = 0.0), while the R isolate was 100% identical to P. expansum accession JN872743.1 (E value 0.0). To evaluate if Scholar applied to apple fruits at the labeled rate before or after inoculation with either an R or S P. expansum isolate could control decay, ‘Golden Delicious’ apples were dipped in Scholar SC or sterile water, wounded, and inoculated with 20 µl of a 1 × 104 conidia ml−1 suspension of either isolate, and stored at 25°C for 9 days. Twenty apples were inoculated for each treatment per experiment, which was repeated. Water-only treated and uninoculated fungicide-treated fruit served as negative controls and were symptomless. Water-dipped P. expansum-inoculated fruit had 100% decay, while P. expansum-inoculated fruit treated with Scholar SC were asymptomatic. In contrast, when fruit were wounded, inoculated with either the R or S isolate, and then dipped in the labeled rate of the Scholar SC fungicide, 78% decay incidence was observed for both isolates 8 days post inoculation. This is the first report of P. expansum with reduced sensitivity to fludioxonil obtained from presizing water at a commercial facility in Pennsylvania with a history of Scholar fungicide use. Repeated exposure to Scholar by P. expansum isolates with reduced sensitivity to fludioxonil may facilitate the development of resistant isolates able to cause decay on fruit during storage. Findings from this research impact current disease control management strategies for pome fruits in the Pennsylvania area given the limited (3) number of control options coupled with documented resistance to thiabendazole and pyrimethanil in the literature.