Infestation of Polish Agricultural Soils by Plasmodiophora Brassicae Along The Polish-Ukrainian Border

There has been a rapid, worldwide increase in oilseed rape production that has resulted in enormous intensification of oilseed rape cultivation, leading to tight rotations. This in turn, has caused an accumulation of pests as well as foliar and soil-borne diseases. Recently, clubroot has become one of the biggest concerns of oilseed rape growers. Clubroot is caused by the soil-borne protist Plasmodiophora brassicae Woronin. The pathogen may be present in groundwater, lakes, and irrigation water used in sprinkling systems. It can be easily transmitted from one field to another not only by water, but also by soil particles and dust transmitted by wind and on machinery. The aim of our overall study was to check for P. brassicae infestation of Polish agricultural soils. This paper presents the 2012 results of a study performed along the Polish-Ukrainian border in two provinces: Lublin (Lubelskie Voivodeship) and the Carpathian Foothills (Podkarpackie Voivodeship), in south-east Poland. Monitoring was done in 11 counties, including nine rural and two municipal ones. In total, 40 samples were collected, out of which 36 were collected from fields located in rural areas and four from municipal areas, with two per municipal region. Each sample was collected at 8-10 sites per field, using a soil auger. The biotest to detect the presence of P. brassicae was done under greenhouse conditions using seedlings of the susceptible Brassicas: B. rapa ssp. pekinensis and the Polish variety of oilseed rape B. napus cv. Monolit. Susceptible plants grown in heavily infested soils produced galls on their roots. A county was regarded as free from the pathogen, if none of the bait plants became infected. The pathogen was found in three out of 40 fields monitored (7.5%) in the Carpathian Foothill region. The fields were located in two rural counties. The pathogen was not found in Lublin province, and was also not detected in any of the municipal counties. The detection with a biotest was fully confirmed by PCR-based molecular detection of P. brassicae DNA in soil samples

Effect of Meiotic Polyploidisation on Selected Morphological and Anatomical Traits in Interspecific Hybrids of <i>Brassica oleracea</i> × <i>B</i>. <i>napus</i>

In Brassica, interspecific hybridisation plays an important role in the formation of allopolyploid cultivars. In this study, the ploidy of F1 and F2 generations resulting from interspecific hybridisation between B. oleracea inbred lines of head cabbage (B. oleracea L. var. capitata) (2n = 18) and kale (B. oleracea L. var. acephala) (2n = 18) with inbred lines of rapeseed (B. napus L.) (2n = 38) was examined by flow cytometry analysis and chromosome observation. Furthermore, the effect of meiotic polyploidisation on selected phenotypic and anatomical traits was assessed. The F1 hybrids of head cabbage × rapeseed (S3) and kale × rapeseed crosses (S20) were allotriploids with 2n = 28 chromosomes, and nuclear DNA amounts of 1.97 (S3) and 1.99 pg (S20). These values were intermediate between B. oleracea and B. napus. In interspecific hybrids of the F2 generation, which were derived after self-pollination of F1 hybrids (FS3, FS20) or by open crosses between F1 generation hybrids (FC320, FC230), the chromosome numbers were similar 2n = 56 or 2n = 55, whereas the genome sizes varied between 3.81 (FS20) and 3.95 pg 2C (FC230). Allohexaploid F2 hybrids had many superior agronomic traits compared to parental B. napus and B. oleracea lines and triploid F1 hybrids. In the generative stage, they were characterised by larger flowers and flower elements, such as anthers and lateral nectaries. F2 hybrids were male and female fertile. The pollen viability of F2 hybrids was comparable to parental genotypes and varied from 75.38% (FS3) to 88.24% (FC320), whereas in triploids of F1 hybrids only 6.76% (S3) and 13.46% (S20) of pollen grains were fertile. Interspecific hybrids of the F2 generation derived by open crosses between plants of the F1 generation (FC320, FC230) had a better ability to set seed than F2 hybrids generated from the self-pollination of F1 hybrids. In the vegetative stage, F2 plants had bigger and thicker leaves, larger stomata, and significantly thicker layers of palisade and spongy mesophyll than triploids of the F1 generation and parental lines of B. oleracea and B. napus. The allohexaploid F2 hybrids analysed in this study can be used as innovative germplasm resources for further breeding new vegetable Brassica crops at the hexaploid level