Abstract

The comparative organogenesis of Brassica napus L cultivars Cyclone, Star and Westar was studied. The cotyledonary explants gave a higher response to all the combinations of 0.5 mg/L 2,4-Dichlorophenoxyacetic acid (2,4-D) and benzylamino purine (BAP; 0.5, 1.0,1.5 and 2.0 mg/L) used for optimizing the conditions for callus induction. The best mean weight and mean length of callus was obtained at 0.5 mg/L 2,4-D and 1.5 mg/L BAP for Star cotyledonary explants. For the increased rooting and thus complete plant regeneration, a shock or a new method of exposing the explants culture to growth regulator free medium for seven days was performed followed for shooting on MS medium with growth regulators. The method was applicable to both hypocotyl and cotyledonary explants. The Shoot Induction Frequency for hypocotyl (6-34%) in the three cultivars is higher than the cotyledonary explants (3-23%). The method is speedy and almost all the shoots and some unshooted calli (78%) form roots on the same media without prior transfer to rooting medium. The analysis of variance (P<0.05) showed that the data is significantly different, and all the variation is due to the different groups/sources in the experiments. Thus, it is recommended to use separate explants of each variety for gene transformation, especially hypocotyl explants of Westar.

Key words: Tissue culture, regeneration, Brassica napus, hypocotyle, cotyledon.