Regeneration and Rooting of Canola (Brassica napus L.) Cultivars Using Growth Regulator-Free and Auxin-Cytokinin Combinations

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The genus Brassica includes some of the very important crop species and is one of the most economically important genera in the Brassicaceae family (syn. Cruciferae). 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 were 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 explant culture to growth regulator-free medium for seven days was performed, followed by shoot 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 of 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 are significantly different and all the variation is due to the different groups/sources in the experiments. In conclusion, a brief shock treatment can significantly enhance the rooting and regeneration potential of Canola cultivars when cultured on growth regulator-free MS medium for seven days. Thus, it is recommended to use separate explants of each variety for gene transformation, especially hypocotyl explants of Westar.

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