Priming is a treatment applied for seed enhancement. Brassica vegetable seeds are commonly affected by Alternaria brassicicola. The changes in germination and vigour of kohlrabi (Brassica oleracea L. var. gongylodes L.) seeds subjected to two priming methods in the presence of A. brassicicola were investigated. The following treatments were applied: uninoculated non-primed seeds (control), seeds inoculated with A. brassicicola (2∙104 spores ml-1), uninoculated and inoculated seeds hydroprimed for 1–2 days, and uninoculated and inoculated seeds osmoprimed for 1–4 days. The percentage of germinating seeds, germination capacity, the percentages of diseased seedlings and dead seeds were determined. The speed of germination, tetrazolium staining index, and electrical conductivity described seed vigour. The presence of A. brassicicola on/in seeds was confirmed on CW semiselective agar. Osmopriming was conducive to penetration of A. brassicicola into kohlrabi seeds. The presence of the fungus had no influence on the percentage of germinating seeds, but a significantly lower germination capacity and a higher percentage of diseased seedlings and dead seeds were observed after inoculation. Non-primed inoculated seeds germinated faster than uninoculated ones. Despite the presence of A. brassicicola, osmotic priming improved seed vigour as measured by the speed of seed germination and electrical conductivity. The results of the tetrazolium vigour test showed its limited usefulness for seeds heavily infected with A. brassicicola.
Kohlrabi is a fast growing, cool season vegetable cultivated primarily for its enlarged stem, which is rich in nutritional components, especially vitamin C and potassium. In two factorial experiment conducted in 2004-2006 there was estimated the effect of plastic covers (perforated plastic film, non woven agrotextile) and plant density (20x15, 25x20 cm) on yield and nutritional value of kohlrabi cultivated in spring season. The significant highest early and marketable yields were obtained from plots covered with agrotextile. The higher density of plants resulted in increased kohlrabi yield. Kohlrabi cultivated under covers had lower level of dry matter, reducing and total sugars. There was not observed the effect of covers on vitamin C concentration. Kohlrabi grown in spacing 20x15 cm contained higher amount of nitrates, vitamin C and reducing sugars in comparison to spacing 25x20 cm.