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2.9 BRIEF REVIEW OF IN VITRO CULTURE
Literature review
The term ”tissue culture” is actually a misnomer inherited from the field of animal
tissue culture. Plant micropropagation involves the culture of a whole individual from
isolated tissues, while animal tissue culture involves the culture of isolated tissues
(KYTE & KLEYN, 1996).
According to AHLOOWALIA et al. (2002), the process of micropropagation can be
divided into five stages: the pre-propagation step (stage 0); the initiation of explants
(stage I); the subculture of explants for multiplication or proliferation (stage II);
shooting and rooting of the explants (stage III); and hardening off the cultured
individuals (stage IV). The pre-propagation stage involves preparing the explant for
aseptic culture.
The explant and its response in vitro is significantly influenced by the phytosanitary
and physiological conditions of the donor plant (KANE, 2004). Plant material used in
clonal propagation should be taken from mother plants that have undergone the
appropriate pre-treatment with fungicides and pesticides to minimize contamination in
the in vitro cultures (AHLOOWALIA & PRAKASH, 2002). Such a piece of plant
material is called an explant (SMITH, 2000b). A single explant can theoretically
produce an infinite number of plants (KYTE & KLEYN, 1996). Explants can be
obtained from meristems, shoot tips, macerated stem pieces, nodes, buds, flowers,
peduncle pieces, anthers, petals, pieces of leaf or petiole, seeds, nucellus tissue,
embryos, seedlings, hypocotyls, bulblets, bulb scales, cormels, radicles, stolons,
rhizome tips, root pieces or protoplasts (KYTE & KLEYN, 1996). The explants should
be surface decontaminated with antibiotic sprays before they are introduced into
culture (AHLOOWALIA et al., 2002; KANE, 2004).
In stage I an aseptic culture is initiated by inoculating the explant onto a sterile
medium (AHLOOWALIA et al., 2002). Once such an explant is established it can be
multiplied a number of times (AHLOOWALIA et al., 2002). The explants are then
transferred to a contaminant free in vitro environment (AHLOOWALIA et al., 2002).
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