Funding: The publication is supported by the EFOP-3.6. 1-16-2016-00022 project. The project is co-financed by the European Union and the European Social Fund. Plant Dis. 106: 767, 2022; published online as https://doi. org/10.1094/PDIS-07-21-1472-PDN. Accepted for publication 17 August 2021.

Watercress (Nasturtium officinale) is an aquatic dicotyledonous vegetable belonging to Brassicaceae (Aiton 1812). Watercress was grown in an aquaponic system on fired clay ball medium at the Aquaponic Research Station of the University of Debrecen, in the city of Debrecen (Hungary). During January 2020, 3-month-old plants showed symptoms in aquaponic cultivation. A visual survey showed 30% of plants with symptoms. Leaves and stems withered and showed white cotton-like mycelium. Mycelia from infected plants were placed on potato dextrose agar (PDA) and incubated at 25 C for 7 days. Single hyphal tips were transferred to produce a pure culture. All 10 fungal isolates showed similar morphological characteristics on PDA. Colonies consisted of white mycelia after 3 days, and globoid to irregular and black 2.5 to 7 (average, 3) mm (n= 100 from 10 plates) sclerotia formed 10 days later, which are the typical morphological features of Sclerotinia sclerotiorum (Mordue et al. 1976). Molecular identification was performed with one of the 10 isolates (Scl_B). Mycelia were grown in 250 ml of potato dextrose broth in a rotary shaker at 175 rpm at 24 C for 6 days. DNA was extracted from mycelium using a NucleoSpin plant II (Macherey-Nagel, Germany) according to the manufacturer, s protocol. Polymerase chain reaction (PCR) amplification (Kim et al. 2014) was performed with primers ITS1/ITS4 for the internal transcribed spacer (ITS) region (White et al. 1990) on a Primus 96 thermal cycler (MWG Biotech, Germany). Specific PCR was