An innovatory protocol for large-scale production of narcissus ‘Carlton’ somatic embryos was developed based on the repetitive somatic embryogenesis (RSE). RSE was established as a stepwise process beginning with primary somatic embryogenesis (PSE) on ovary explants followed by secondary somatic embryogenesis (SSE) and continuously repeating cycles of SSE. A highly embryogenic lines of callus were sourced from primary embryogenic tissue, callus and embryos, which were continuously exposed to Amino-3,5,6-trichloropicolinic acid (Picloram) or 2,4-Dichlorophenoxyacetic acid (2,4-D) (both 25 µM) and 6-Benzyladenine (BA) (5 µM). Thus obtained calluses were multiplicated in six-week repetitive cycles and the efficiency of multiplication was 2.1- to 2.3-fold. Using RSE protocol, on regeneration medium containing 5 µM BA and 0.5 µM α-Naphthaleneacetic acid (NAA) it was possible to receive more than 20 embryos per 100 mg of callus. PSE yielded only 3.3–11 embryos. RSE resulted in the production of cream-coloured soft calluses which retained high efficiency of multiplication and differentiation of somatic embryos for over two years.

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