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Multiple resistance of Plasmopara viticola to QoI and CAA fungicides in Brazil
Author(s) -
Santos Ricardo F.,
Fraaije Bart A.,
Garrido Lucas da R.,
MonteiroVitorello Cláudia B.,
Amorim Lilian
Publication year - 2020
Publication title -
plant pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.928
H-Index - 85
eISSN - 1365-3059
pISSN - 0032-0862
DOI - 10.1111/ppa.13254
Subject(s) - plasmopara viticola , biology , downy mildew , pyrosequencing , fungicide , veterinary medicine , genetics , botany , gene , medicine
Grapevine downy mildew, caused by Plasmopara viticola , is commonly controlled by quinone outside inhibitor (QoI) and carboxylic acid amide (CAA) fungicides. QoI resistance is conferred by a mutation resulting in a G143A alteration in cytochrome b , while CAA resistance is associated with a G1105S mutation in cellulose synthase 3. The aims of this study were to (a) verify the presence of QoI and CAA resistance in P . viticola in Brazil, (b) develop a single nucleotide polymorphism (SNP) detection pyrosequencing assay for quantitative detection of G143A, and (c) determine the geographic prevalence and distribution of G143A and G1105S in Brazilian field populations. P . viticola isolates were sampled from two vineyards reporting failures of QoI and CAA control. Their growth was unaffected by azoxystrobin and mandipropamid, and resistance was associated with the G143A and G1105S mutations, respectively. The SNP detection pyrosequencing assay developed for G143A detection was precise and accurate. Pyrosequencing assays revealed that G143A and G1105S frequencies varied among the 66 field populations and were positively correlated with the number of QoI and CAA applications, respectively. The G143A mutation was observed in 60 populations, 39 of them with frequencies over 90%. G1105S was detected in 20 populations with frequencies ranging from 18.3% to 100%, and which also carried the G143A mutation. Multiple resistance to QoI and CAA in P . viticola was confirmed for the first time in South America. Future resistance monitoring surveys and management strategies must be adopted to prevent further increase in QoI and CAA resistance in Brazil.