Ef®cient plant regeneration from multiple shoots formed in the leaf-derived callus of Lavandula vera, using the `̀ open culture system''

To develop an ef®cient procedure for plant regeneration from leaf-derived callus of Lavandula vera DC, the production of multiple shoots and the formation of roots from these shoots were studied. When calli were cultured in a medium with 4.0 10ÿ7 M N-(2-chloro-4-pyridyl)-N0phenylurea (CPPU), urea-type cytokinin, multiple shoots were obtained from the greenish surface of the callus ef®ciently at a rate of 52.2%. For multiple shoot development, the shoots were divided into 7±20 shoot clusters with 2±3 shoots and subcultured every 2 weeks. Two modi®ed culturesystems were employed for subculture; a `̀ closed culture system'' and an `̀ open culture system''. In the open-system, shoot clusters grew and elongated vigorously. In the closed-system, most of the clusters showed vitri®cation and did not elongate. In root induction culture, shoot clusters in the open-system were well rooted and grew vigorously, the highest rate of root formation being 74.0%, in the 1 2 MS medium supplemented with 1.0 10ÿ6 M indoleacetic acid (IAA). On the other hand, shoot clusters in the closed-system showed vitri®cation and did not root well. About seven times more regenerants were obtained from the multiple shoots than from normal shoots treated with 4.4 10ÿ6 M 6-benzylamino purine (BA), a purine-type cytokinin. These results indicate that ef®cient plant regeneration in L. vera from callus using multiple shoots is possible by means of an open-system. # 2000 Elsevier Science B.V. All rights reserved.