Table 4.
Origin of Plasmodiophora brassicae field isolates, the related field information, and the results of pathotype classification. Isolates were collected from four field experiments and from one clubroot-infested field in southern and central Sweden from 2017 to 2020.
| Frequency of OSR in a Rotation (Years) |
Mean Value of DI per Region in Clubroot-Infested Fields (%) 3 |
Pathotype Classification 4 | |||||
|---|---|---|---|---|---|---|---|
| Isolate 1 | Region 2 | Soil pH | ECD Code | Somé 1996 | DSI on OSR cv. Mendel | ||
| 1 | NA | 6.1 | 6 | 100 ± 0.0 | 16/23/28 | P1 | 8 |
| 2 | NA | 6.4 | 6 | 16/23/29 | P1 | 27 | |
| 3 | SC | 6.5 | 4 | 47.56 ± 19.76 | 16/31/31 | P1 (+) | 47 |
| 4 | SC | 6.5 | 4 | 16/23/29 | P1 | 22 | |
| 5 | SC | 6.9 | 4 | 16/31/31 | P1 (+) | 75 | |
| 6 | SC | 6.9 | 4 | 16/31/31 | P1 (+) | 57 | |
| 7 | SC | 6.9 | 4 | 16/31/31 | P1 (+) | 63 | |
| 8 | SC | 6.9 | 4 | 16/31/28 | P1 (+) | 43 | |
1 Isolate 1: Susceptible cultivar mix (cvs Avatar, Dariot and Explicit); Isolate 2 and Isolate 4: farm field cv Atora; Isolate 3: susceptible cultivar mix (cvs Avatar, Dariot and Explicit; Isolate 4: susceptible cultivar mix (cvs Avatar, Dariot and Explicit); Isolate 5: clubroot-resistant cultivars Croozer and Crocodile; Isolate 6: clubroot-resistant RNX 193207; Isolate 7: clubroot-resistant cultivar DK Plastic Isolate; 8: susceptible cultivar mix of cvs. Harnas, Avatar, Explicit and Mercedes. Origin of isolates. 1; Hallsberg, 2; Örebro, 3; Simrishamn, 4; Tommelilla, 5–8; Höganäs. 2 Regions in Sweden. NA: Närke; SC: Scania. 3 Mean value of disease incidence (DI) in clubroot-infested field experimental plots in each county. The incidence of disease in each clubroot-infested field was estimated by randomly choosing 25 plants. The presence of any swelling or gall formation on the root was assumed as proof of P. brassicae infection. 4 Classification was done according to the differential systems of the European Clubroot Differential set (ECD; [19]) and Somé et al. [20]. A cut-off point of the disease severity index (DSI) of 25% was used to classify plant reactions as resistant or susceptible [20].