Survey on the prevalence of R hizoctonia spp. in E uropean soils and determination of the baseline sensitivity towards sedaxane

The prevalence of R hizoctonia spp. in European soils was determined by analysing soil samples from 282 locations. R hizoctonia spp. were found in 68% of these samples from France, Germany, the UK , Poland, Italy, Spain, Hungary and the Czech Republic. Samples from 136 locations were further analysed by pyrosequencing. Seventy‐six percent of the isolates were R hizoctonia solani and 24% binucleate R hizoctonia spp. Rhizoctonia solani anastomosis group ( AG ) 5 was detected most frequently (25%), followed by AG 9 (16%) and AG 4 (13%). For the binucleate Rhizoctonia spp., AG E was most prevalent (13%). Rhizoctonia cerealis was not detected in soil samples. Soil type or cropping history had no effect on the type of Rhizoctonia observed. Rhizoctonia solani AG 5 was the most frequently detected AG irrespective of the previous crop. The spectrum of AG s detected was similar for France, Germany and Poland but was significantly different for the UK ( P = 0·0016). Finally, the baseline sensitivity towards sedaxane, a new active ingredient for seed treatment, was analysed for all isolates. The results indicate a low baseline sensitivity (average EC 50 of 0·028 p.p.m.) for all Rhizoctonia AG s. No difference in sensitivity was observed with the isolates obtained from different countries.