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Poster: Biology & Disease Mgmt: Chemical Control


Investigating dynamics of QoI fungicide resistance in potato early blight complex pathogens in Wisconsin
S. DING (1), K. Meinholz (1), A. Gevens (1) (1) University of Wisconsin-Madison, U.S.A.

The potato early blight complex (EBC), caused by Alternaria solani and A. alternata, is a perennial and destructive fungal disease that can lead to loss in yield and quality. Without cultivar resistance, management is with weekly-applied fungicides which can result in pathogen resistance in commercial fields treated with single site mode of action fungicides. One such group is the QoIs, which target the cytochrome b of pathogens. In this 2015 study, the F129L mutation which leads to QoI partial resistance was detected in all A. solani isolates collected from 4 farms representing unique potato production regions of Wisconsin. Three of the farms conducted conventional production practices; one farm was certified organic. QoI resistance in A. alternata was due to the G143A mutation and was detected in 64% of the isolates in early July, and 91% in late August. At the organic farm, the percentage of A. alternata isolates with QoI resistance increased from 0 to 13% over the season. It is possible that A. alternata, with a broad host range, may have a wild type preserved in alternative hosts which can move into potato. Alternaria solani, which is more specifically a potato pathogen, may have been subjected to QoI selection more thoroughly. Our results suggested that there was rapid selection for QoI resistance within a single production season, indicating the need for modified and integrated management responses for long term management of the EBC.