Somaclonal variation arises from genetic changes in plants regenerated from tissue culture. The document discusses the history, types, causes and applications of somaclonal variation. It notes that somaclonal variants first observed in 1969 have since led to disease resistant crops. Variations can be genetic, epigenetic or chromosomal and result from tissue culture conditions. Both desirable variants like stress tolerance and random variants are obtained. Selection methods are used to isolate variants with desired traits for crop improvement.

1. SOMACLONAL VARIATION AND
ITS SIGNIFICANCE

2. CONTENTS
• Introduction
• Brief History
• Source and selection of somaclonal variation
• Kinds and types of variation
• Causes
• Application
• Advantages and disadvantages
• Conclusion
• Reference

3. INTRODUCTION
• “Soma” mean Vegetative and “clones” means the Identical copy.
• Genetic variation in plants arising from undifferentiated cells during tissue culture
is called somaclonal variation.
• The name somaclonal variation was coined by Larkin and Scowcroft in 1981.
• Tissue cultured plants which have genetic characters not seen in parent plants are
known as somaclonal variants.
• Somaclonal variations is not restricted to, but is particularly common in, plants
regenerated from callus. somaclonal variants raised from Calli are called Calli
clones, those raised from cells are called cell clones and those raised from
protoplast are called protoclones. If genetic variability is established in plants by
culturing gametic cells, then it is said to be gametoclonal variation.

4. BRIEF HISTORY
• S.K. Pillai (1969) observed variability in plant populations raised from
tissue culture of geranium.
• M. Krishnamurthi (1974) isolated disease resistant variants of
sugarcane from tissue culture.
• J.F. Shepard, D. Bidney and E. Shahin (1980) isolated potato variant
plant lines.
• D. A. Evans and W.R. Sharp (1983) analyzed somaclonal variations in
a large number of plants regenerated from leaf explants of tomato.

5. SOURCE MATERIAL FOR SOMACLONAL
VARIATION
• Somaclonal variation can be created both in monocots and
dicots.
• The regeneration source can be callus, protoplasts,
adventitious shoots, anthers,pollens or individual cells.
• It is known to occur both in asexually and sexually
reproducing plants.

6. SELECTION OF SOMACLONAL
VARIATIONS
Without Selection Pressure
• In this method, no selection pressure is applied to the tissue culture.
No toxin or inhibitory substance is added to the culture. The cells or
tissues are cultured in vitro into calli and plantlets are regenerated
from the calli.
 With Selection Pressure
• In this method, first a selection pressure is applied to cell or tissue
culture and then variant cell lines are screened from the culture to
regenerate plantlets from them.

7. KINDS OF VARIATIONS
Cytogenetic
• Deletion which is found partial chromosomal loss after breakage.
• Inversion and interchange that show intrachromosomal breakage and reunion.
Genetic
• The variations are associated with point mutation where base sequence alteration was
found.
Epigenetic
• The epigenetic variation is found in a process where alteration in DNA methylation
takes place and this variation is due to cytokinin habituation

8. TYPES OF VARIATIONS
Late replicating heterochromatin
• In replication process, heterochromatic regions of the chromosome
replicate later than euchromatic segments. This character can be
vulnerable to fluctuations in the mitotic cell cycle.
• In late replication of heterochromatin certain “shocks” to the genome
caused the activation of transposable elements. This activation is the
outcome of tissue culture.

9. Chromosomal aberration
• The changes in chromosome numbers in regenerated plants have
been the major clue for complete understanding of somaclonal
variation.
Cytoplasmic gene changes
• In somaclonal variants the chloroplast or mitochondrial genes exist in
high frequency.

10. CAUSES OF S.C VARIATIONS
The causes may be
Genetic
Physiological
Biochemical

11. GENETIC
• Pre-existing variations in the somatic cells of explant that are caused by
mutations and other DNA changes.
• Typical genetic alterations are
1.Changes in chromosome numbers (polyploidy and aneuploidy)
2.Change in chromosome structure (translocations, deletions and duplications)
3.DNA sequence (base mutations)
• Occur at high frequency

12. PHYSIOLOGICAL
• Exposure of culture to plant growth regulators
• Culture conditions
BIOCHEMICAL
• Lack of photosynthetic ability due to alteration in carbon
metabolism
• Antibiotic resistance

13. ISOLATION OF S.C VARIATION
Phenotypic characters
• This is a long term technique for isolation of somaclonal variations.
Cytological technique
• As the cells of the variants show increase in chromosome number and
morphology, the traditional squash technique was employed.

14. Biochemical technique
• Assay of biochemical products of regenerated plant extracts plant parts
have an important parameter for detection of the somoclonal
variations.
Stress tolerance
• The capacity of certain regenerated plants is to tolerate different
environmental stresses like high temperature, mineral toxicity, salt,
water logging
Pathogenic technique
• The pathogen is selected for isolation of the somaclonal variations.

16. ISOLATION OF S.C VARIANTS
 Without in vitro selection
 Within vitro selection

17. Without in Vitro Selection:
• An explant (leaf, stem, root etc.) is cultured on a suitable
medium, supplemented with growth regulators. The
unorganized callus and cells do not contain any selective
agent (toxic or inhibitory substance). These cultures are
normally sub-cultured, and transferred to shoot induction
medium for regeneration of plants. The so produced plants are
grown in pots, transferred to field, and analyzed for
somaclonal variants
• Somaclonal variants of several crops have been successfully
obtained by this approach e.g., sugarcane, potato, tomato,
cereals etc.

18. Limitations of without in vitro selection approach
• There is no directed and specific approach for the isolation of
somaclones without in vitro selection. Consequently, the appearance
of a desired trait is purely by chance. Further, this procedure is time
consuming and requires screening of many plants

20. With in Vitro Selection
• Isolation of somaclones with in vitro selection method basically involves
handling of plant cells in cultures (protoplast, callus) like microorganisms
and selection of biochemical mutants. The cell lines are screened from
plant cultures for their ability to survive in the presence of a
toxic/inhibitory substance in the medium or under conditions of
environmental stress.
• The differentiated callus, obtained from an explant is exposed in the
medium to inhibitors like toxins, antibiotics, amino acid analogs.
Selection cycles are carried out to isolate the tolerant callus cultures and
these calli are regenerated into plants. The plants so obtained are in vitro
screened against the toxin (or pathogen or any other inhibitor).

21. • The plants resistant to the toxin are selected and grown further by
vegetative propagation or self-pollination. The subsequent generations
are analyzed for disease resistant plants against the specific pathogenic
organism.
• Besides the disease resistant plants, plants with herbicide resistance and
antibiotic resistance have also been developed with in vitro selection
approach.

22. Advantages of with in vitro selection approach:
• The major advantage of with in vitro selection method is the specific
selection of the desired trait rather than a general variation found at the
plant level. This procedure is less time consuming when compared to
without in vitro selection approach.

24. FACTORS RESPONSIBLE FOR
VARIATION
Ploidy
• The chromosomal changes or the ploidy influences the frequency and
nature of the variation. In general, polyploids exhibit greater somaclonal
variation than diploids
Procedure in tissue culture
• Protoplast regeneration is associated with more somaclonal variation
than regeneration from cell explants. this clearly indicates the possibility
of the role of tissue culture procedure in somaclonal variation

25. Media composition
• The variation in chromosome number can be influenced by the addition
of different types of growth regulators in the medium. Hence, the media
composition is one of the factor its controlling the somaclonal variation
in tissue culture
Genotype
• The variations observed in different plants are not of same frequency i.e.
in begonia haemalis there is 43% of regenerates are variant in one variety
while only 7% are variant in another variety. From the evidences it can be
assumed that there is a genotypic component to instability in culture

26. Tissue source
• The different frequencies of somaclonal variations are found in
different types of tissues. Thus the tissue source is the one of the
factors in somaclonal variations. In chrysanthemum, difference in
somaclonal variations were found between petal and pedicel
derived plants. Differences in stability between different pea tissues
have been reported as the stem callus being more stable than root
callus.

27. APPLICATIONS OF S.C VARIATIONS
• Production of agronomically useful plants
• Resistance to disease
• Resistance to abiotic stresses
• Resistance to herbicides
• Improved seed quality and geraniums(esp. scented varieties)
• Woody ornamentals

28. ADVANTAGES OF S.C VARIATIONS
• Help in crop improvement
• Creation of additional genetic variations
• Increased and improved production of secondary metabolites
• Selection of plants resistant to various toxins, herbicides, high salt
concentration and mineral toxicity
• Suitable for breeding of tree species

29. DISADVANTAGES OF S.C VARIATIONS
• A serious disadvantage occurs in operations which require clonal
uniformity, as in the horticulture and forestry industries where
tissue culture is employed for rapid propagation of elite genotypes
• Sometime leads to undesirable results
• Selected variants are random and genetically unstable
• Require extensive and extended fields trials
• Not suitable for complex agronomic traits like yield, quality etc.
• May develop variants with pleiotropic effects which are not true.

30. CONCLUSION
Somaclonal variation is a valuable tool in plant
breeding, wherein variation in tissue culture
regenerated plants from somatic cells can be used in
the development of crops with novel traits.

31. REFERENCE
• Shekhawat.M.S.,(2010).Plant Cell and Tissue Culture. Saras
publication,Kanyakumari, pp- 145-162
• https://www.slideshare.net/SharmasClasses/somaclonal-variation-
and-its-crop-improvement-248395910
• https://www.slideshare.net/mobile/RIZWANABBAS3/plant-
regeneration-and-somaclonal-variations
• https://www.slideshare.net/RakeshKumar440/somaclonal-variation-
26537134

32. THANK YOU