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Int.J.Curr.Microbiol.App.Sci (2018) 7(7): 3778-3786
International Journal of Current Microbiology and Applied Sciences
ISSN: 2319-7706 Volume 7 Number 07 (2018)
Journal homepage: http://www.ijcmas.com
Review Article https://doi.org/10.20546/ijcmas.2018.707.438
A Review on Plant Tissue Culture, A Technique for Propagation and
Conservation of Endangered Plant Species
1,2 1 1
Ojo Michael Oseni *, Veena Pande and Tapan Kumar Nailwal
1
Department of Biotechnology, Kumaun University, Nainital,
Bhimtal Campus, Bhimtal-263136, India
2Department of Botany, Obafemi Awolowo University, Ile-Ife, Nigeria
*Corresponding author
ABSTRACT
Keywords
Plant tissue culture has been widely employed in area of agriculture,
Plant tissue culture, horticulture, forestry and plant breeding. It is an applied biotechnology used
Propagation, for mass propagation, virus elimination, secondary metabolite production
Conservation, and in-vitro cloning of plants. Recently, plant tissue culture has been used
Endangered plant
for the conservation of endangered plant species through short and medium
Article Info
term conservation also known as slow growth and cryopreservation also
Accepted: known as long term conservation. These methods had been successfully
26 June 2018
used to conserve plant species with recalcitrant seeds or dormant seeds and
Available Online:
10 July 2018 showed greater advantage over the conventional methods of conservation.
Introduction as the direct or indirect cause of most modern
extinctions. The primary threats to these
Conservation of natural resources is the wise species include residential and commercial
use of the earth's resources by humanity. development; overexploitation via fishing,
Usher (2000) defined conservation as the hunting, or collecting; disturbance by humans
maintenance of genetic, species, and during work and recreational activities;
ecosystem diversity in the natural abundance pollution; and the introduction of exotic
in which they occur. Thomas (2003) sees species (Venter et al., 2006; Prugh et al.,
conservation as the sacrifice of immediate 2010; McCune et al., 2013).
rewards in return for delayed ones. As the
global human population approaches eight The two main methods of conserving
billion, there is growing concern about the rate biodiversity are: ex-situ and in-situ
of extinction of other species that inhabit our conservation. Ex-situ conservation is the
planet (Barnosky et al., 2011; Dirzo et al., process of protecting or preserving an
2014). Compelling evidence points to humans endangered species of either plants or animal
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outside of its natural habitat either by In-vitro organ culture offers an alternative
removing whole or part of that population source for the conservation of endangered
from the threatened habitat and placing it in a genotypes (Sengar et al., 2010), which can be
new environment which may be a wild area or achieved using slow growth (short and
within human control environment. Methods medium term conservation) procedure or
of ex-situ conservation are Biological cryopreservation (long-term conservation)
Gardens, Seed bank, Gene bank, Germplasm (Scherwinski-Pereira et al., 2010). Tissue
bank and In-vitro storage. While in-situ culture protocols can be used for preservation
conservation involves the conservation and of plant tissues or organ when the targets for
preservation of species in their natural habitat conservation are clones instead of seeds. This
in places where the species naturally occurs. helps to keep the genetic background of a crop
Under this method the entire ecosystem is and to avoid the loss of the conserved
protected and maintained so that all the patrimony due to natural disasters, whether
constituent species, both known and unknown biotic or abiotic stress (Tyagi et al., 2007).
are conserved. The main methods of in-situ The plant species which do not produce seeds
conservations are: Strict nature reserve (SNR), (sterile plants) or which have „recalcitrant‟
Games Reserve and National Park. In-situ seeds that cannot be stored for long period of
conservation has been made almost impossible time can successfully be conserved via in-vitro
due to the disappearance of large wild areas as techniques for the maintenance of gene banks.
a result of natural disasters, pests, pathogens The method also reduced storage space for
and threats from changing government maintaining a large number of explants in an
policies and urban development. Ex-situ aseptic environment, the stored materials are
Conservation is very difficult to carry out due readily available for use and it can be easily
to the following problems: an adequate sample seen to be alive.
has to be taken for the conservation of genetic
diversity, land space requirement is very Plant tissue culture
important, particularly in the case of forest
trees which are very large, whereas land Plant tissue culture is the in vitro aseptic
availability drastically decreases, labour costs culture of cells, tissues, organs or whole plant
and trained personnel (Engelman, 1991). under controlled nutritional and environmental
conditions (Thorpe, 2007) often to produce the
Plant tissue culture is a modern method of clones of plants. The resultant clones are true-
propagation and conservation of plant species. to type of the selected genotype. The
Apart from their use as a tool of research, controlled conditions provide the culture an
plant tissue culture techniques have in recent environment conducive for their growth and
years, become of major industrial importance multiplication. These conditions include
in the area of plant propagation, disease proper supply of nutrients, pH medium,
elimination, plant improvement and adequate temperature and proper gaseous and
production of secondary metabolites. Small liquid environment. Plant tissue culture
pieces of tissue (named explants) can be used technology is being widely used for large
to produce hundreds and thousands of plants scale plant multiplication. Apart from their use
in a continuous process. A single explant can as a tool of research, plant tissue culture
be multiplied into several thousand plants in techniques have in recent years, become of
relatively short time period and space under major industrial importance in the area of
controlled conditions, irrespective of the plant propagation, disease elimination, plant
season and weather on a year round basis improvement and production of secondary
(Akin-Idowu et al., 2009). metabolites. Small pieces of tissue (named
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Int.J.Curr.Microbiol.App.Sci (2018) 7(7): 3778-3786
explants) can be used to produce hundreds and obtained in controlled conditions (Singh,
thousands of plants in a continuous process. A 1992).
single explant can be multiplied into several
thousand plants in relatively short time period Plant tissue culture medium contains all the
and space under controlled conditions, nutrients required for the normal growth and
irrespective of the season and weather on a development of plants. It is mainly composed
year round basis (Akin-Idowu et al., 2009). of macronutrients, micronutrients, vitamins,
Endangered, threatened and rare species have other organic components, plant growth
successfully been grown and conserved by regulators, carbon source and some gelling
micropropagation because of high coefficient agents in case of solid medium. Murashige
of multiplication and small demands on and Skoog medium (MS medium) is most
number of initial plants and space. In addition, extensively used for the vegetative
plant tissue culture is considered to be the propagation of many plant species in vitro.
most efficient technology for crop The pH of the media is also important that
improvement by the production of somaclonal affects both the growth of plants and activity
and gametoclonal variants. The of plant growth regulators. It is adjusted to the
micropropagation technology has a vast value between 5.4 - 5.8. Both the solid and
potential to produce plants of superior quality, liquid medium can be used for culturing. The
isolation of useful variants in well-adapted composition of the medium, particularly the
high yielding genotypes with better disease plant hormones and the nitrogen source has
resistance and stress tolerance capacities profound effects on the response of the initial
(Brown and Thorpe, 1995). Certain type of explant. Plant growth regulators (PGR‟s) play
callus cultures give rise to clones that have an essential role in determining the
inheritable characteristics different from those development pathway of plant cells and
of parent plants due to the possibility of tissues in culture medium. The auxins,
occurrence of somaclonal variability (George cytokinins and gibberellins are most
1993), which leads to the development of commonly used plant growth regulators. The
commercially important improved varieties. type and the concentration of hormones used
Commercial production of plants through depend mainly on the species of the plant, the
micropropagation techniques has several tissue or organ cultured and the objective of
advantages over the traditional methods of the experiment (Ting, 1982). Auxins and
propagation through seed, cutting, grafting cytokinins are most widely used plant growth
and air-layering etc. It is rapid propagation regulators in plant tissue culture and their
processes that can lead to the production of amount determined the type of culture
plants virus free (Garcia-Gonzales et al., established or regenerated. The high
2010). Coryodalis yanhusuo, an important concentration of auxins generally favors root
medicinal plant was propagated by somatic formation, whereas the high concentration of
embryogenesis from tuber-derived callus to cytokinins promotes shoot regeneration. A
produce disease free tubers (Sagare et al., balance of both auxin and cytokinin leads to
2000). Meristem tip culture of banana plants the development of mass of undifferentiated
devoid from banana bunchy top virus (BBTV) cells known as callus. Maximum root
and brome mosaic virus (BMV) were induction and proliferation was found in
produced (El-Dougdoug and El-Shamy, 2011). Stevia rebaudiana, when the medium is
Higher yields have been obtained by culturing supplemented with 0.5 mg/l NAA (Rafiq et
pathogen free germplasm in vitro. Increase in al., 2007). Cytokinins generally promote cell
yield up to 150% of virus-free potatoes was division and induce shoot formation and
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Int.J.Curr.Microbiol.App.Sci (2018) 7(7): 3778-3786
axillary shoot proliferation. High cytokinin to embryos. Highest efficiency of embryonic
auxin ratio promotes shoot proliferation while callus was induced by culturing nodal stem
high auxin to cytokinins ratio results in root segments of rose hybrids on medium
formation (Rout, 2004). Shoot initiation and supplemented with various PGR‟s alone or in
proliferation was found maximum, when the combination (Xiangqian et al., 2002). This
callus of black pepper was shifted to medium embryonic callus showed high germination
supplemented with BA at the concentration of rate of somatic embryos when grown on
0.5 mg/l (Hussain et al., 2011). abscisic acid (ABA) alone. Somatic
embryogenesis is not only a process of
Somatic embryogenesis regenerating the plants for mass propagation
but also regarded as a valuable tool for genetic
Somatic embryogenesis is an in vitro method manipulation. The process can also be used to
of plant regeneration widely used as an develop the plants that are resistant to various
important biotechnological tool for sustained kinds of stresses (Bouquet and Terregrosa,
clonal propagation. It is a process by which 2003) and to introduce the genes by genetic
somatic cells or tissues develop into transformation (Maynard et al., 1998). A
differentiated embryos. These somatic successful protocol has been developed for
embryos can develop into whole plants regeneration of cotton cultivars with resistance
without undergoing the process of sexual to Fusarium and Verticillium wilts (Han et al.,
fertilization as done by zygotic embryos. The 2009).
somatic embryogenesis can be initiated
directly from the explants or indirectly by the Organogenesis
establishment of mass of unorganized cells
named callus. Plant regeneration via somatic Organogenesis is refered to the production of
embryogenesis occurs by the induction of plant organs i.e. roots, shoots and leaves that
embryogenic cultures from zygotic seed, leaf may arise directly from the meristem or
or stem segment and further multiplication of indirectly from the undifferentiated cell
embryos. Mature embryos are then cultured masses (callus). Plant regeneration via
for germination and plantlet development, and organogenesis involves the callus production
finally transferred to soil and differentiation of adventitious meristems
into organs by altering the concentration of
Somatic embryogenesis has been reported in plant growth hormones in nutrient medium.
many plants including trees and ornamental Skoog and Muller (Skoog and Miller, 1957)
plants of different families. The phenomenon were the first who demonstrated that high ratio
has been observed in some cactus species of cytokinin to auxin stimulated the formation
(Torres-Munoz and Rodriguez-Garay, 1996). of shoots in tobacco callus while high auxin to
There are various factors that affect the cytokinin ratio induced root regeneration.
induction and development of somatic
embryos in cultured cells. A highly efficient Slow growth of cultured plants
protocol has been reported for somatic
embryogenesis on grapevine (Jayasankar et Slow growth is usually achieved by reducing
al., 1999) that showed higher plant the culture temperature, by modifying culture
regeneration sufficiently when the tissues media with supplements of osmotic agents and
were cultured in liquid medium. Plant growth growth inhibitors, or by removing growth
regulators play an important role in the promoters to reduce the cellular metabolism of
regeneration and proliferation of somatic the material, striving to maximize the time
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