High Frequency Regeneration through Somatic Embryogenesis in Bacopa monnieri (L.) Wettest, an Important Medicinal Plant

Bacopa monnieri is well known in the Indian system of medicine or Ayurveda as brahmi or water hyssop and has been using as a brain tonic and to cure mental disorders. An efficient in vitro protocol for high frequency regeneration has been developed via somatic embryogenesis from the leaf explants of two months old Bacopa monnieri (L.) Wettest. plants grown under greenhouse conditions. A high frequency of embryoids formed after the transfer of fleshy, nodular, leaf-derived callus onto Murashige and Skoog (MS) medium supplemented with 0.5 mg l -1 2,4-D (2,4-dichloro-phenoxy acetic acid). A mean of 42.20 ± 2.20 embryoids developed per callus mass mean of 1.09 ± 0.06. An increase in the concentration above 1.5 mg l -1 of 2,4-D reduced the embryonic potentiality of the callus. Fluorescent staining of the embryogenic callus with auramine O stain revealed the occurrence of the embryogenic callus and facilitated the observation of the occurrence of globular, cordate and torpedo embryos and the subsequent differentiation of vasculature in the embryoids. The isolated cotyledonary embryoids matured and induced multiple shoots and roots on both MS basal medium and MS medium fortified with 1 to 1.5 mg l -1 6-benzylaminopurine, i.e., BAP. Each plantlet obtained from an embryoid, could further produce multiple shoots on MS basal medium from which a mean of 28.6±1.37 plantlets were harvested. Most regenerants (98%) were successfully hardened-off and transferred to the field and maintained for the evaluation of variation. The present system of somatic embryogenesis of B. monnieri could be a viable system for the improvement of this medicinal crop.