© 2013 Plant Management Network.
Emergence of Single Point Mutation in PvCesA3, Conferring Resistance to CAA Fungicides, in Plasmopara viticola Populations in Japan
Yoshinao Aoki, Maki Hashimoto, and Shunji Suzuki, Laboratory of Fruit Genetic Engineering, The Institute of Enology and Viticulture, University of Yamanashi, Kofu, Yamanashi 400-0005
Corresponding author: Shunji Suzuki. firstname.lastname@example.org
Aoki, Y., Hashimoto, M., and Suzuki, S. 2013. Emergence of single point mutation in PvCesA3, conferring resistance to CAA fungicides, in Plasmopara viticola populations in Japan. Online. Plant Health Progress doi:10.1094/PHP-2013-0729-01-BR.
Mandipropamid, one of the carboxylic acid amide (CAA) fungicides, was registered for control of grapevine downy mildew disease (caused by Plasmopara viticola) in June 2009 in Japan and its use was started in the 2010 growing season. Almost simultaneously with the registration of mandipropamid in Japan, the increasing occurrence of quinone outside inhibitor fungicide resistance in P. viticola populations became a serious problem in Japan (4). Because of this, mandipropamid was widely used in Japanese vineyards. Dimethomorph and benthiavalicarb-isopropyl, other CAA fungicides, were registered in 1999 and 2000 in Japan, respectively. However, dimethomorph has been hardly used for control of grapevine downy mildew disease.
In Europe, mandipropamid-resistant P. viticola isolates were detected as early as in 2004 (5). A single point mutation from GGC to AGC in codon 1105 of PvCesA3, which resulted in a single amino acid substitution of serine for glycine, confers mandipropamid resistance to P. viticola (3). Mandipropamid fungicide resistance is recessively inherited (5). Heterozygotes harboring resistant and susceptible PvCesA3 alleles are susceptible to mandipropamid fungicide, whereas homozygotes harboring the mutation in both alleles only express resistance (3). Therefore, to inhibit the spread of CAA fungicide-resistant P. viticola, we have to recognize the emergence of the mutation in P. viticola populations.
Downy mildew infected leaves were collected from two vineyards located in Yamanashi Prefecture, the major grape-growing region in Japan, in September 2012. Mandipropamid was first applied to both vineyards in the 2011 growing season (Table 1), and then applied to vineyard A in the 2012 growing season. Benthiavalicarb-isopropyl, another CAA fungicide, was also applied to vineyard A in both years. As control samples, downy mildew infected leaves were collected from three vineyards to which CAA fungicides had never been applied. The detection of mandipropamid-resistant PvCesA3 was performed by the PCR-restriction fragment length polymorphism (PCR-RFLP) assay (1) and the allele-specific primer PCR (ASP-PCR) assay (2).
Table 1. Fungicide management programs in vineyards sampled.
x CAA fungicide.
Consequently, we detected the mandipropamid-resistant PvCesA3 from one of the 35 single-lesion samples collected from vineyard A (Fig. 1a and 1b). DNA sequencing demonstrated that a single point mutation from GGC to AGC in codon 1105 occurred in the PvCesA3 of the sample (Fig. 1c). In contrast, the resistant allele was not detected in any of the 21 samples collected from vineyard B. Furthermore, no mutation in codon 1105 of the PvCesA3 allele was detected in 164 samples collected from three vineyards to which mandipropamid had never been applied. As DNA sequencing also detected a non-mutated codon 1105 in PvCesA3 clones amplified from the sample by PCR, we judged that the sample might have been a susceptible heterozygote to mandipropamid or that it might have been a heterogeneous population among susceptible and resistant P. viticola isolates. This is the first report that the resistant PvCesA3 allele has been emerged in P. viticola populations in Japan.
The risk for CAA fungicide resistance in P. viticola is evaluated as ‘moderate’ (5). To data, the grape grower in vineyard A has not experienced a loss of efficiency of CAA fungicides against downy mildew. We cannot rule out the possibility that the use of benthiavalicarb-isopropyl promoted the emergence of G1105S mutation in PvCesA3, although benthiavalicarb-isopropyl had never been applied to the vineyards sampled prior to 2011.
1. Aoki, Y., Furuya, S., and Suzuki, S. 2011. Method for rapid detection of PvCesA3 gene allele conferring resistance to mandipropamid, a carboxylic acid amide fungicide, in Plasmopara viticola populations. Pest Manag. Sci. 67:1557-1561
2. Aoki, Y., Hada, Y., and Suzuki, S. 2013. Development of multiplex allele-specific primer PCR assay for simultaneous detection of QoI and CAA fungicide resistance alleles in Plasmopara viticola populations. Pest Manag. Sci. 69:268-273
3. Blum, M., Waldner, M., and Gisi, U. 2010. A single point mutation in the novel PvCesA3 gene confers resistance to the carboxylic acid amide fungicide mandipropamid in Plasmopara viticola. Fung. Gen. Biol. 47:199-510
4. Furuya, S., Mochizuki, M., Saito, S., Kobayashi, H., Takayanagi, T., and Suzuki, S. 2010. Monitoring of QoI fungicide resistance in Plasmopara viticola populations in Japan. Pest Manag. Sci. 66:1268-1272
5. Gisi, U., Waldner, M., Kraus, N., Dubuis, P. H., Sierotzki, H. 2007. Inheritance of resistance to carboxylic acid amide (CAA) fungicides in Plasmopara viticola. Plant Pathol. 56:199-208.