Somatic Embryogenesis of Pathogen- Free Horseradish (Armoracia Rusticana) Plants in Vitro

Abstract

Illinois had been the major producer of horseradish in the United States for many years. Horseradish root production in Illinois had recently decreased due to a disease complex that causes root discoloration and rots. The use of pathogen-free (PF) horseradish planting stock was a means for the Illinois horseradish growers to restore root quality and yields. Micropropagation of PF plants through tissue culture could be used to deliver PF planting stock to growers, but it was time-consuming and has high labor costs. In addition, the growers needed millions of plants to supply their planting stock needs. It had been proposed to develop a method to produce whole plants from single cells via somatic embryogenesis. To initiate somatic embryogenesis, the Illinois Horseradish ‘Doll’ cultivar (‘Doll’) was tested with 2,4 -D (0.25 to 1.0 mg/l) and BA in vitro. Somatic embryogenic callus was successfully induced from leaf explants on MS medium supplemented with 2, 4-D. Somatic embryos (SEs) were collected from the callus, germinated, and converted to whole plants. Histological studies of SEs showed that they developed from cells near the vascular bundles. Furthermore, SEs developed through stages that mimicked normal embryo development. SEs germinated to give healthy and vigorous horseradish plants. Since cell suspensions of somatic embryogenic calli yielded plants, it raised the possibility to generate large number plantlets from suspension cultures. In addition, it was predicted that SEs could be encapsulated to make “artificial seeds” that could be used to supply a certified set program.