Protocols for Micropropagation of Woody Trees and Fruits

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2.6. Storage of in Vitro Cultures
O. PÉREZ-TORNERO AND L. BURGOS
In vitro repositories of valuable plant genotypes offer a number of advantages over
conventional methods. Greenhouse space and maintenance are reduced, and the stored
material is protected from insect pests and pathogens and can be micropropagated
rapidly when desired. Minimal growth storage is a very simple technique that allows
storage of plants in vitro for long period of time.
Figure 8. Acclimatization tunnel.
The main objective of the minimal growth procedure is the extension of the normal
subculture interval from 2–6 weeks to a much longer period (up to 12 months). It
also increases flexibility in micropropagation and overcomes temporary difficulties
in production. The common procedure requires incubation of in vitro plantlets at
reduced temperature and low light intensity (or in darkness).
In vitro apricot shoots can be stored for at least 6 months without subculture
(Pérez-Tornero et al., 1999b) when they are stored at 3° C on the proliferation
medium in darkness (Figure 9). Normal proliferation rates are obtained after storage
and shoots can be rooted and acclimatized.
3. CONCLUSIONS
Apricot cultivars can be efficiently micropropagated with the methodology
described here. In vitro introduction and establishment are better achieved if axillary
shoots are used as original explants. However, when internal contaminants are a
serious problem, the culture of meristem tips overcomes this problem. A modified
QL medium is ideal for proliferation of apricot shoots, whilst hyperhydricity
problems, often presents in apricot cultures, can be controlled by using a bottom
cooling system. Rooting of apricot shoots can be obtained readily but apical necrosis