SOMATIC EMBRYOGENESIS AND PLANT-REGENERATION IN TISSUE-CULTURES OF RADISH (RAPHANUS-SATIVUS L)

Hypocotyl segments of 2- to 3-week-old radish (Raphanus sativus L. cv. F-1 Handsome Fall) seedlings produced yellowish compact calli when cultured on Murashige and Skoog's (MS) medium supplemented with 1 mgI(-1) 2,4-dichlorophenoxyacetic acid (2,4-D). Upon transfer onto medium containing 6-benzyladenine and alpha-naphthaleneacetic acid, up to 5.3% of the calli gave rise to a few somatic embryos. When subcultured for 3 to 6 months, 7% of the yellowish compact calli produced white, compact calli which formed numerous embryos. These calli maintained their embryogenic capacity for over 18 months. When cultured on medium containing 0.1 to 3 mgl(-1) 2,4-D, up to 90% of longitudinally sliced somatic embryo halves produced calli with numerous secondary embryos. Embryos were transferred onto medium containing 0.1 mgl(-1) 2,4-D and 1 mgl(-1) abscisic acid where they developed into the cotyledonary stage. Upon transfer onto half-strength MS basal medium, approximately 90% of the embryos developed into plantlets. These plantlets were successfully transplanted in potting soil and after cold treatment they were grown to maturity in a phytotron.