EFFECT OF SILVER NITRATE ON IN VITRO REGENERATION AND ANTIOXIDANT RESPONSES OF OILSEED RAPE CULTIVARS (BRASSICA NAPUS L.)

We studied a stimulatory effect of silver nitrate on callus formation and shoot regeneration of five oilseed rape commercial varieties Ability, Lagonda, Lancia, Menthal and Mirakel (Brassica napus L.). Hypocotyls were induced to organogenesis on the media supplemented with silver nitrate at concentration 5 mg.L1 and without silver nitrate as a control. After 2 weeks of cultivation, calli on the media with silver nitrate became deep green in colour. First shots appeared after 4 weeks of cultivation on the media with silver nitrate. Calli formed on the control media were pale green and did not form any shoots or at very low efficiency. Silver nitrate improved regeneration efficiency from 0- 0.8% to 8.3-10% in varieties Albina, Lancia and Menthal. Explants of Lagonda and Mirakel did not form any calli and these varieties appeared to be recalcitrant. Analyses of six weeks-old calli showed that silver nitrate increased concentration of photosynthetic pigments, which is a good prerequisite for cell regeneration. Silver nitrate increased malondialdehyde level and induced changes in enzyme activities of antioxidants ascorbate peroxidase and catalase; and in the accumulation of non-enzymatic antioxidant proline; in the genotype dependant manner. The results suggest that an activation of stress response was necessary to obtain shoots with higher frequency in the varieties Albina, Lancia and Menthal.