Link to home

Cannot retrieve the URL specified in the Content Link property. For more assistance, contact your site administrator.

Complex Patterns of Resistance to Respiration Inhibitors Revealed among Corynespora cassiicola Isolates from Tomato in Florida
Keevan MacKenzie: Gulf Coast Research & Education Center; Aimin Wen: University of Florida; Gary Vallad: Gulf Coast Research and Education Center, University of Florida; Heather Adkison: Univ of Florida GCREC; Late Lawson Hellu: Gulf Coast Research & Education Center
<div>Target spot caused by Corynespora cassiicola is one of the most economically important foliar and fruit diseases of tomato in Florida. From 2015 to 2017, 105 isolates collected from 7 tomato producing counties in Florida were evaluated for sensitivity to 7 respiration inhibitor fungicides, including quinone outside inhibitors (QoI) and succinate dehydrogenase inhibitors (SDHI), based on mycelial growth inhibition (MGI), spore germination (SG), and sequence-based analyses. Nearly 90% of the isolates were resistant to the QoI fungicides azoxystrobin and fenamidone based on MGI and SG with EC<sub>50</sub> > 10 ppm. Additional sequence-based screening of cytB confirmed the presence of the G143A mutation in all but one of the QoI resistant isolates identified by MGI. Based on MGI, 75.2% of the C. cassiicola isolates exhibited reduced sensitivity to one or more of the tested SDHI fungicides, including boscalid, penthiopyrad, fluxapyroxad, benzovindiflupyr, and fluopyram. Cross-resistance to all 5 SDHI fungicides was evident in one isolate, while 39% of the isolates exhibited reduced sensitivity to all but fluopyram. In planta assays and sequence analysis of sdhB, C, and D subunits from representative isolates are being peformed to further corroborate MGI results. Enhanced knowledge of fungicide resistance among C. cassiicola isolates will improve the management of target spot and help limit further development of fungicide resistance in Florida.</div>

View Presentation