Seeds of all accessions were sterilized in 70% (v/v) ethanol for 2–3 min, 10% (w/v) chloramine T (Biochemie Poland, Katowice, Poland) for 20 min, and washed three times with sterile distilled water for 5 min. Seeds were germinated on MS (Murashige and Skoog 1962) medium supplemented with 0.8% (w/v) agar (Biocorp, Warszawa,
Poland). In order to obtain plantlets with well-developed leaves, seeds were placed in sterile 250 ml glass jars containing 30 ml of MS medium, and kept at 26±2°C under 16 h photoperiod with light intensity 55 μmol m−2 s−1. Etiolated hypocotyls were obtained from seeds placed in 9 cm Petri dish with 5 ml of MS medium, kept in the dark at 26± 2°C.