Multiple resistance of Plasmopara viticola to QoI and CAA fungicides in Brazil

Abstract

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.

Lack of an Intron in Cytochrome b and Overexpression of Sterol 14α-Demethylase Indicate a Potential Risk for QoI and DMI Resistance Development in Neophysopella spp. on Grapes

“…Since the launch of QoIs into the market in 1996, several ascomycetes and oomycetes have developed resistance to this fungicide group that is, in most cases, associated with the CYTB G143A target alteration (Ishii and Hollomon 2015;Lucas et al 2015). Although QoIs have been extensively used in the management of grapevine diseases including AGLR, anthracnose, downy mildew, and powdery mildew, there are a limited number of studies on QoI fungicide resistance in Brazil (Santos et al 2020). In our study, no nucleotide sequence variation in the CYTB gene was found among the 55 Neophysopella isolates that carried wild-type alleles at codons 129, 137, and 143.…”

“…The G143A mutation is associated with high levels of QoI resistance, and F129L and G137R are associated with moderate resistance (Fern andez-Ortuño et al 2008). QoI control failures have been commonly reported in grapevine powdery and downy mildew populations carrying the G143A mutation (Miles et al 2021;Santos et al 2020). In rusts, only the F129L mutation has been reported in † Corresponding author: L. Amorim; lilian.amorim@usp.br Phakopsora pachyrhizi (Klosowski et al 2016).…”

New insights from short and long reads sequencing to explore cytochrome b variants of Plasmopara viticola populations collected in vineyard and related to resistance to complex III inhibitors

“…In this particular case however, RT-PCR assay design failed to analyse the two insertions of six nucleotides observed in P. viticola cyt b gene, their detection relying on the pyrosequencing approach only. Allele quantification using pyrosequencing technology has been used for SNP detection and quantification of QoI and CAA fungicides resistance in P. viticola [39,40]. In other hand, target site modification related to succinate dehydrogenase inhibitors (SDHI) resistance in Pyrenophora teres were identified using pyrosequencing [41].…”

Fungicide Resistance Evolution and Detection in Plant Pathogens: Plasmopara viticola as a Case Study

“…Resistance to different fungicide modes of action in P. viticola has been reported ( Table 1 ) in the main vine-growing areas ( Figure 2 ) using different detection techniques [ 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 ].…”

“… Global vine-growing areas allocated for the production of wine grapes, table grapes, or dried grapes in 2018 (sources Organisation of Vine and Wine and ood and Agriculture Organization of the United Nations) ( A ), compared to countries where P. viticola fungicide resistance was reported in 2020 ( B ) [ 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 ]. …”