Pathotypes of Plasmodiophora brassicae causing damage to oilseed rape in the Czech Republic and Poland

Veronika Řičařová,Jan Kazda,Victor Manolii,Pavel Rysanek,Joanna Kaczmarek,Stephen E Strelkov,Wolfgang Lueders,Malgorzata Jedryczka

doi:10.1007/s10658-016-0939-1

Abstract

Winter oilseed rape (Brassica napus) is an important crop in the Czech Republic and Poland. Clubroot disease caused by the pathogen Plasmodiophora brassicae is a serious and still-growing problem for oilseed rape growers in both countries. The aim of this study was to evaluate the pathotype composition of P. brassicae populations from the Czech Republic and Poland, according to the three evaluation systems, and to determine soil inoculum loads for representative fields via traditional end-point PCR as well as quantitative PCR analysis. There were considerable differences between the populations of P. brassicae from both countries, and the number of pathotypes varied depending on the evaluation system and the threshold used to distinguish susceptible vs. resistant plant reactions. This is the first study comparing the effect of different thresholds. Using an index of disease (ID) of 25 % to distinguish susceptible vs. resistant reactions, there was a total of seven pathotypes identified based on the differentials of Williams, five with the system of Some et al., and 18 with the European Clubroot Differential (ECD) set. However, based on a threshold of 50 %, there were nine pathotypes according to the evaluation system by Williams, four based on the differentials of Some et al., and 15 with the ECD set. Changing of the thresholds led to the reclassification of some pathotypes. Several pathotypes were common in both countries. High amounts of pathogen DNA were found in many of the field soils analysed by quantitative PCR. There was a weak correlation between soil pH and infestation of P. brassicae for the Polish soils.

Highlights

Clubroot, caused by Plasmodiophora brassicae Woronin, is a serious soilborne disease of the Brassicaceae family
Clubroot occurs throughout the Czech Republic, mainly on cruciferous vegetables (Rod 1994; Kopecky et al 2012; Chytilova and Dusek 2007), as well as in Poland, where it was found on vegetables and oilseed rape (Korbas et al 2014)
On European Clubroot Differential (ECD) 15, index of disease (ID) ranged from 0 % ± 0 % to 52 % ± 2 %, indicating that this genotype was moderately resistant to P. brassicae

Summary

Introduction

Clubroot, caused by Plasmodiophora brassicae Woronin, is a serious soilborne disease of the Brassicaceae family. In recent years clubroot has become a serious problem on farms growing spring and winter oilseed rape (Brassica napus L.) (Dixon 2009). Clubroot occurs throughout the Czech Republic, mainly on cruciferous vegetables (Rod 1994; Kopecky et al 2012; Chytilova and Dusek 2007), as well as in Poland, where it was found on vegetables and oilseed rape (Korbas et al 2014). The disease occurs in large areas cultivated to oilseed rape, primarily in the northern and south-western regions of the country; clubroot infestations extend to the borders with Belarus and the Ukraine (Jedryczka et al 2014; Korbas et al 2014). The main agricultural plain (Mazovia, Greater Poland) is relatively free of the disease, likely because of lower rainfall, better regulation of soil pH, and good agricultural practices including appropriate crop rotation (Jedryczka et al 2013)

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