Stem canker of brassicas, also known as blackleg is the most damaging disease of many Brassicaceae. The disease is caused by Leptosphaeria maculans (Desm.) Ces et de Not. and L. biglobosa sp. nov., Shoemaker & Brun, which coexist in plants and resulting in disease symptoms and decreased yield, quantity and quality of cultivated vegetables and oilseed rape. The paper presents taxonomic relationships between these coexisting pathogen species, describes particular stages of their life cycles, summarizes the differences between the species, and reviews methods for their identification.

Clubroot, caused by Plasmodiophora brassicae, is a crucial oilseed rape disease worldwide. Information on the virulence of P. brassicae populations is essential to apply disease control with proper clubroot-resistant cultivars. In 2016–2020, 84 isolates of P. brassicae were collected in the Czech Republic (CZ), Germany (DE), Poland (PL), and Sweden (SW). Pathotypes were designated using 17 Brassica hosts, including the European Clubroot Differentials (ECD), Somé set, and clubroot-resistant oilseed rape cv. Mendel. According to the ECD set, virulence analyses differentiated the isolates into 42 pathotypes. The most common pathotypes were 16/31/31 (in DE, PL, and SW) and 16/06/12 (in CZ, DE, and PL). Six pathotypes were found according to the Somé set, including 1–4 pathotypes per country. P1 was most prevalent in DE, PL, and SW, while P3 was abundant in CZ, DE, and PL. The current study provides clear evidence for a shift towards increased virulence in P. brassicae populations compared to previous studies. Several isolates overcame the resistance of cv. Mendel and of Brassica rapa genotypes ECD 01 to ECD 04. Considering all investigated samples, significant negative correlations were found between clubroot incidence and the frequency of oilseed rape in crop rotation, as for clubroot incidence and soil pH.

Clubroot is a damaging disease of oilseed rape and vegetable brassicas worldwide, caused by the soil-borne protist Plasmodiophora brassicae Wor. Due to the long life of resting spores, the assessment of the pathogen abundance in agricultural fields can serve as a guideline for disease control at the country-wide level or the regional scale. Between 2013 and 2019, we collected 431 soil samples from fields cultivated with Brassicaceae crops throughout 16 provinces of Poland. The samples were subjected to qPCR based analysis of P. brassicae DNA concentration. From these data, the spore loads and gene copies g⁻¹ soil were calculated and used to produce an assessment of the current clubroot risk potential at a country-wide and regional scale. The country-wide map, showing the spread of the pathogen in agricultural soils, was made using ArcGis software package implementing the interpolation with the Inverse Distance Weight method. The calculation of gene copies specific to P. brassicae helped to formulate the recommendations for farmers in respect to the cultivation guidelines. It showed a high risk of yield losses in defined regions of north, south-west and central Poland and an urgent need to undertake intensive preventative measures.

LAMP is an innovative, simple, rapid, specific and cost-effective nucleic acid amplification method. Due to the use of a special enzyme – GspSSD polymerase, the reaction takes a short time and can be performed at isothermal conditions. The sensitivity and specificity of LAMP technique is significantly higher, than standard PCR techniques, as two or three specific primer pairs are used. The technique is regarded as a useful tool for the detection and identification of plant pathogens. In this work, LAMP was used to study the composition of the population of fungi of the genus Leptosphaeria, causing a damaging disease of oilseed rape, called blackleg or stem canker. The detection concerned DNA present in fungal spores contained in air samples obtained using Hirst-type volumetric trap, in Pomerania (north Poland) in 2010. The results achieved using the LAMP technique were similar to these obtained with previously used, highly specific method of Real-time PCR. Conducting LAMP reaction was much easier and less time-and cost-consuming, due to a simplified method of DNA isolation of pathogens from plant tissues. Then, the LAMP technique was used to assess the composition of the population of Leptosphaeria spp. in plants of oil- seed rape collected from the field in the Opole region (south-we- stern part of Poland) in 2013. In contrast to studies conducted in 2002–2003, the analysis of leaf symptoms showed a higher pro- portion of L. maculans compared to L. biglobosa, what reflects changes in the composition of pathogen population of fungi causing blackleg on oilseed rape in this part of Poland.