Synthetic Seeds of Asparagus Officinalis L.

There are numerous studies on in vitro clonal propagation of plant species. Asparagus (Asparagus officinalis L.) is dioecious and highly heterozygous. The plants are usually raised from seeds and the resulting seedlings contain equal proportions of male and female plants. Male plants are desirable because of their higher spear yield. Clonal propagation by division of the crowns is possible but the multiplication rate is low (Reuther, 1984). Therefore, tissue culture is an important method used to propagate superior selected plants to obtain high and uniform yield. There are mainly two tissue culture methods: (i) the conventional micropropagation by nodal sections or lateral buds and, (ii) by somatic embryogenesis. There are two major difficulties with the conventional micropropagation methods. Firstly, it is difficult to mechanize the tissue culture operation. The lack of ability to mechanize results in a costly product because of high labour costs. Secondly, the difficulty in rooting the explants results in low process yields, which in turn increases the cost of the resulting plants. On the other hand, mechanization is easier with somatic embryogenenic systems, especially when the somatic embryos (SEs) are produced in a liquid medium. Furthermore, somatic embryogenesis systems have high multiplication rates. Many studies have reported somatic embryogenesis in asparagus (Wilmar and Hellendoorn, 1968; Saito et al., 1991; Delbreil et al., 1994; Li and Wolyn, 1995).