Rooting Induction in Encapsulated Buds of M.26 Apple Rootstock for Synthetic Seed

Abstract

In 1993, Redenbaugh reported that the term “synthetic seed” (synseed) should be referred only to an encapsulated somatic embryo. In more recent years, synthetic seeds were defined as artificially encapsulated somatic embryos, shoots or other vitro-derived tissues that can be used for sowing under in vitro or ex vitro conditions (Aitken-Christie et al., 1995). It seems logical, therefore, that the terminology that was initially set up for somatic embryo synthetic seeds be now used for any kind of encapsulated expiant. The term “conversion” was explained as growth and development of both shoot and root systems, with minimal swellings, callus production, etc. In one word, “conversion” expresses the production of a green plant with a normal phenotype from a synthetic seed (Redenbaugh et al., 1988; Redenbaugh, 1993). When the above described criteria are met, it seems justified that the term “conversion” can be reasonably used to describe the development of a full plantlet from any synseed, either made from a bipolar (somatic embryo) or an unipolar explant. Talking about synseeds, there are other terms that should instead be avoided, such as “germination”, which is proper of the real seed, or “plantlet formation”, which can generally be related to any way of producing a small rooted plant from micropropagated units (Debergh and Read, 1991). Furthermore, the term “regrowth” should be used to indicate any other vegetative act different from conversion that is performed by an encapsulated propagule after sowing, such as rooting or sprouting or emission of a leaf, etc.