Comparison of real‐time PCR tests for the detection of Synchytrium endobioticum resting spores in soil and their potential application in descheduling of previously infested plots

Abstract

AbstractPlots infested with Synchytrium endobioticum, the causal agent of potato wart disease, are scheduled, resulting in prohibition of potato cultivation of and cultivation of plants for planting. On account of robust resting spores that are present in infested soils, plots remain scheduled for 20 years. After this period, plots are intensively sampled and the presence of resting spores in soil is determined by direct examination. However, this method is very time‐consuming and labour‐intensive. In this paper, validation data for the molecular detection of resting spores in soil and its use to screen soils before direct examination are reported. In addition to the samples in the validation study, over 670 routine diagnostic samples were analysed by direct examination and molecular tests in parallel. Using an improved methodology, increased sensitivity was obtained relative to results reported from an interlaboratory comparison study in 2018, namely 7 spores per sample instead of 500 spores per sample. Molecular screening of the soil samples and direct examination of those samples testing positive was estimated to reduce the total hands‐on time by half when compared to direct examination of all samples. We recommend inclusion of molecular detection in the update of EPPO PM 3/59 (3) and PM 7/28(2), and suggest that when all subsamples of a plot are negative, no additional direct examination or bio‐assays are needed for descheduling (i.e. for releasing previously infested plots from official control).