Somatic Embryos from Callus of Sugarbeet Biotecllnology Clone REL-l

Abstract

Somatic embryos could be used fo r proliferati ve propagation or for gene transfer procedures in sugarbeet (Beta vulgaris L.) if adequate methods for initiation and development could be devi sed. With sugarbeet model clone REL-1, plating of fresh suspension culture cells grown with hormone-free Murashige and Skoog (MS) medium onto further ho'rmone-free MS medium elicited a low frequency of somatic embryogenesis, about one embryo per ml of suspension used. The incl usion of 0.1 or 0.3 mg/ I abscisic acid (ABA) in the plating medium increased the number of somatic embryos in this system. A combination of naphthaleneacetic acid (NAA) (1 mg/ 1) and ABA (0.1 mg/ 1) gave the highest somatic embryo yield, 15 em­ bryos per ml of suspension. After 22 to 40 days, embryos at various stages, ranging from globular, heart, and torpedo­ shaped embryos to mature opaque white embryos with cotyledons and radicles, were present at the callus surface. The external morphology of several somatic embryos was examin­ ed by scanning electron microscopy. The somatic embryos developed into normal plantlets, including betalain pigmen­ tation on hypocotyls, after being transferred onto hormone­ free MS medium. The conversion rate of somatic embryos of different lengths (1 , 2, 3 mm) into complete plantlets was si milar (78, 81 and 86070, respectively). Secondary em­ bryogenesis, which would be useful in providing somatic em­ bryos for gene transfer purposes, was not observed in this study.