Naphthaleneacetic Acid Solely Induced Extensive Hairy Root Development that Precedes Extensive Shoot Regeneration from Stalk Explants of Cauliflower (Brassica Oleracea Var. Botrytis)

A reliable, rapid, and single step strategy for in vitro regeneration of true-to-type cauliflower (Brassica oleracea var. Botrytis) plants is described. Mature stalk disc explants cultured on Murashige and Skoog (MS) medium supplemented with 2 mg l -1 naphthaleneacetic acid (NAA) regenerated entire plants within one month. During the first 18 days, hairy roots developed intensively before the regeneration of shoots (on average 52 shoots per 1-cm disc explant) on the same MS medium plus 2 mg l -1 NAA. Stem elongation and full plantlet development were successfully achieved within 10 days on MS medium without plant growth regulators, followed by plantlets transplantation into soil. This rapid and large scale propagation protocol was faster, easier and showed higher frequency of shoot induction comparing to the routine shoot-then-root organogenesis protocols using various combinations of cytokinins. On the other hand, NAA solely induced callus and hairy roots, but with poor shoot regeneration from cauliflower floret curd tissues compared to that from stalk disc explants.