|MACARISIN, OTILIA - University Of Maryland
|PETER, KARI - Pennsylvania State University
Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/2/2016
Publication Date: 12/22/2016
Citation: Jurick II, W.M., Macarisin, O., Gaskins, V.L., Park, E., Yu, J., Janisiewicz, W.J., Peter, K.A. 2016. Characterization of postharvest fungicide-resistant Botrytis cinerea isolates from commercially stored apple fruit. Phytopathology. 107:362-368.
Interpretive Summary: Grey mold is caused by a fungus that occurs on apple fruit in the field and during long term cold storage. It is one of the main problems for the apple growing industry and is controlled by fungicides. However, the number of chemicals used to control this fungus are limited and it is imperative that the most effective materials are used to combat decay and minimize losses. Resistance to postharvest fungicides in the grey mold fungus was discovered for the first time in Pennsylvania at a commercial fruit packinghouse. Our results provide evidence for grey mold resistance to multiple fungicides and novel mechanisms of resistance that have not been previously reported. The results from this research are valuable to apple growers, packers, and processors so that they can use the most effective fungicide products to limit decay, maintain fruit quality, and reduce losses. Our results are also valuable for scientists conducting research to develop DNA-based diagnostic tests that will rapidly detect fungicide-resistant grey mold strains and help guide fungicide management decisions.
Technical Abstract: Botrytis cinerea causes grey mold of apple fruit and is one of the most economically important postharvest pathogens of global concern. Eight fludioxonil sensitive B. cinerea isolates from Pennsylvania had EC50 values ranging from 0.004 to 0.0038 µg/ml fludioxonil that were dual resistant to pyrimethanil and thiabendazole. Exposure to a sub-lethal concentration of fludioxonil, facilitated subsequent growth on a discriminatory dose for all but one isolate, which were categorized conditionally resistant. Three vigorously growing isolates with conditioned resistance to fludioxonil had EC50 values >50 µg/ml, were osmosensitive, and retained resistance in the absence of selection pressure in vitro. In vivo analysis of representative B. cinerea strains revealed decay failures on fungicide treated apples which confirms their in vitro phenotypes. The Mrr1 R632I mutation, commonly associated with fludioxonil resistance in B. cinerea, was not detected in three fludioxonil resistant B. cinerea isolates suggesting the fungus may be implementing additional mechanism(s) to meditate resistance. Data from this study shows for the first time that dual resistant B. cinerea isolates have the potential to quickly develop resistance to fludioxonil which can manifest in decay failures and may present control challenges for the apple storage and packing industries in the future.