Encapsulation, Germination, and Conversion of Somatic Embryos in Sugarbeet

Sugarbeet (Beta vulgaris L.) somatic embryos of biotech clone REL-2, obtained from callus grown with absci­ sic acid, were encapsulated with 2 % alginate and sub­ sequently germinated and converted into plantlets, in initial efforts necessary for eventual routine produc­ tion of artificial seeds. Factors examined were embryo size, alginate companion solution, cold storage dura­ tion, and germination substrate. Unencapsulated so­ matic embryo length category (0.5-1.9,2.0-2.9, or 3.0­ 3.9 mm) did not affect germination (98,99, 100%) or conversion (87, 89, 87%, respectively) rates into com­ plete plantlets on hormone-free Murashige-Skoog (MS) medium. Alginate companion solutions (either hor­ mone-free MS medium or H 20) had no differential ef­ fect on germination rate (100%) but did differ in con­ verting embryos to plantlets (81 vs. 64%, respectively). Subsequent experiments examining duration of cold storage of encapsulated embryos at 4°C found no lower rate of conversion at 25°C after 21 days of cold com­ pared with unstored embryos, but after 64 days of cold, the germination and conversion rates (70 and 45 %, respectively) at 25°C of embryos encapsulated with alginate in MS medium were lower compared with unstored embryos. With alginate in H20, germination after 64 days of storage at 4°C was 60%, and conver­