Infestation of Polish agricultural soils by Plasmodiophora brassicae on the Polish-Belarussian border in Podlasie province

Abstract: Extensive cultivation of oilseed rape worldwide, leads to tight rotations in regions suitable for the production of this cash crop. Growing of the same plant species on large areas and with only short breaks of crops having different requirements lead to accumulation of pests and diseases. In recent years in Poland a great increase of soil infestation by the soil-borne protist-like pathogen Plasmodiophora brassicae has been observed. This is why we have undertaken a methodical survey of agricultural soils in the whole country. In this paper we present the results of investigations done in 2012 and 2013 in Podlasie province (Podlaskie voivodeship) in counties located along the Polish-Belorussian border. The study was done in six counties, including one municipal county of Bialystok (1 sample) and five rural counties: Augustowski (7), Bialostocki (18), Hajnowski (8), Siemiatycki (9) and Sokolski (7). Apart from one sample from the field located in a municipal area, the samples were collected from 49 fields, 28 of which were located in typically rural communities and 21 originated from urban-rural communities. Sampling was done using a soil auger. Depending on field size, a sample was taken from 8 to 10 locations per field, 200 g of soil per location. In total ca. 1.6 to 2 kg of soil was collected per field. The detection of the presence of P. brassicae was done using a soil test performed in glasshouse conditions at 20 °C, using seedlings of two species of the genus Brassica, susceptible to P. brassicae. Eight weeks after sowing the plants were individually removed from the soil samples and were inspected for the presence on clubs on roots. The pathogen was found in 3 out of 50 fields monitored (6%), with one sample per Bialostocki, Hajnowski and Sokolski county. The pathogen was not found in samples from the field located in Bialystok municipal county. We conclude that the serious occurrence of P. brassicae is occasionally present in agricultural soils in Podlasie province in counties along the Polish-Belarussian border.