Plant Disease (2015) 99, 1347-1352

J.R. Standish, M. Tomaso-Peterson, T.W. Allen, S. Sabanadzovic and N. Aboughanem-Sabanadzovic (2015)
Occurrence of QoI fungicide resistance in Cercospora sojina from Mississippi soybean
Plant Disease 99 (10), 1347-1352
Abstract: Frogeye leaf spot, caused by Cercospora sojina Hara, is a foliar disease affecting soybean (Glycine max (L.) Merr.), often managed by applications of quinone outside inhibitor (QoI) fungicides. In 2013 and 2014, 634 C. sojina monoconidial isolates were collected from soybean fields throughout Mississippi. Initially, in vitro bioassays were performed to evaluate the sensitivity of 14 of 634 isolates plus a baseline. Resistant and sensitive isolates were characterized by determining the effective fungicide concentrations at which 50% of conidial germination was inhibited (EC₅₀). The molecular mechanism of resistance was determined for all 634 isolates, using a PCR-RFLP method and comparing nucleotide sequences of the cytochrome b gene. The state of Mississippi was divided into five distinct geographical regions (the Hills, Delta, Pines, Capital, and Coast) based on estimates of total soybean hectares. The greatest proportion (16.7%) of QoI-sensitive isolates was collected in the Hills while the Coast had no QoI-sensitive isolates. QoI-sensitive isolates from the Pines, Capital, and Delta ranged from 1.6 to 7.0%. Results of this study determined that more than 93% of C. sojina isolates collected in Mississippi carried the G143A amino acid substitution, indicating a shift to a QoI-resistant population throughout Mississippi soybean fields.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Tom W. Allen, Sead Sabanadzovic

Research topic(s) for pests/diseases/weeds:
pesticide resistance of pest

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Cercospora sojina	Soybean (Glycine max)	U.S.A. (mid S)