Virulence and fungicide sensitivity of the most prevalent genotypes collected in Belgium in 2017-2018
- César, V. (2019). Virulence and fungicide sensitivity of the most prevalent genotypes collected in Belgium in 2017-2018.
|Virulence and fungicide sensitivity of the most prevalent genotypes collected in Belgium in 2017-2018
|Phytophthora infestans isolates : Isolates were sampled from naturally infected potato (dumps, volunteers and crops). Single-lesion isolates were obtained by placing pieces of infected tissue on tuber slices of a susceptible potato cultivar (Bintje). Pure cultures were obtained by transferring small pieces of mycelium growing on the upper side of the potato slice on pea agar medium. Genotyping: The isolates were analyzed using standardized 12 plex Euroblight SSR genotyping. Genotypes were determined by comparing fragment sizes with isolates previous genotyped (Euroblight monitoring). Virulence profile: virulence was determined using Black’s differential set of potato clones, each having one of the R1-R11 resistance genes. Virulence was also determined by detached leaf assay on several commercial varieties which have a good rating about resistance in field. Fungicide sensitivity: Metalaxyl sensitivity was assessed using a floating leaf disk method (leaf of potato cv. Bintje). Leaf disk were floated abaxial side up in Petri dishes each containing water or metalaxyl at concentrations of 0 to 100 µg/ml. Each disk was inoculated with 10µl droplet of sporangial suspension. Fluazinam sensitivity was evaluated on potato leaf discs by mixing the fungicide at different concentrations (0,1 - 1 - 10 - 30 and 100mg/L) with the sporangial suspensions. Results: Until 2016, 3 clonal lineages dominated in Belgium: the most prevalent was EU_ 13_A2 clone which made up 50% of the population. The two others were EU_1_A1 and EU_6_A1 and found at low frequency. In 2017, monitoring highlighted the emergence of a new clonal lineage, named EU_37_A2. EU_37_A2 has displaced other lineages and is now dominant in Belgium. Two other genotypes, EU_33_A2 and EU_36_A2 were found in very few cases. EU_13_A2 was resistant to metalaxyl and 33_A2 and 37_A2 were resistant to fluazinam. All known virulence genes were found in Wallonia isolates. EU_ 13_A2 had a more complex virulence profile than other genotypes. Significant differences were observed between genotypes regarding their virulence on resistant varieties.