The document provides a comprehensive overview of somaclonal variation, which refers to genetic variability arising during tissue culture in plants. It discusses the mechanisms, causes, and factors affecting these variations, as well as their applications and limitations in crop improvement. Additionally, it outlines methods for isolating and detecting somaclonal variants, emphasizing their potential benefits for enhancing traits like disease resistance and stress tolerance.

1. SOMACLONAL VARIATION- A
GENERAL ACCOUNT
By
Anupama Paul
MSc. 2nd semester Roll no-
34
Dept. of Life science and
Bioinformatics
Assam University, Silchar

2.  Introduction
 Features
 Mechanism
 Cause of variation
 Factors affecting production of variants
 Isolation of somaclonal variants
 Detection of somaclonal variants
 Applications
 Limitations
Contents

3.  “Soma’’ mean the somatic cells and “clones” means the
generations.
 The term Somaclonal Variation was first coined by
Larkin and Scrowcroft in 1981. (Larkin,1981)
 According to Larkin and Scowcroft , “Somaclonal
variation is the genetic variability which is regenerated
during tissue culture” or plant variants derived from any
form of cell or tissue cultures. (Larkin,1981)
 Genetic variations in plants that have been produced by
plant tissue culture and can be detected as phenotypic
traits.
Introduction

4. The genetic variations are inherited by the clones of
the treated plant.
 Somaclonal variation sometimes may lead to
desirable characteristics like increased pest
resistance etc. .(Jha and Ghosh, 2010).
 This kind of work is majorly done to achieve some of
the beneficial properties of plants like-disease
resistance, stress resistance, nutritional quality
improvement etc.
 The recovery of genetic changes in plants
generated from somatic cells thus offers an
oppurtunity to unravel natural variability and to use
this variation for development of new varities for
plenty of good purposes. (Larkin,1981)
Introduction

5.  Variations for Karyotype, isozyme characteristics and
morphology in somaclones may be observed.
 Calliclone(clones of callus),mericlone (clones of
meristem) and protoclone (clones of Protoplast) are
produced. .(Jha and Ghosh, 2010)
 Generally heritable mutation and persist in plant
population even after plantation into the field.
 Variation occurs in both qualitative and quantitative
traits.(Larkin,1981)
Features

6.  The somaclones that are generated from tissue
culture directly are regarded as Ro or R plants.
 The self fertilized progeny of Ro plants represent
R1plants.
 R2, R3,R4 etc plants are the subsequent
generations.
 Some other workers use other
nomenclature(Ro=SC1) and SC2,SC3,SC4 for
subsequent generations.
Nomenclature of somaclones

7. Somaclonal variation occur as a result of genetic heterogeneity
in plant tissue culture which may be
1. Genetic (Heritable Variations)
• Pre-existing variations in the somatic cells of
explant.
• Caused by mutations and other DNA changes
• Genetic disorders such as polyploidy, aneuploidy,
chromosomal aberrations etc.
• Occur at high frequency. .(Jha and Ghosh, 2010)
2. Epigenetic (Non-heritable Variations)
• Variations generated during tissue culture
• Caused by temporary phenotypic changes
• Due to culture conditions, varied nutrients etc
• Occur at low frequency. (Skirvin etal.1994)
Mechanism

8. Causes of Somaclonal
Variations
Physiological
Cause
Physiological
cause
Genetic cause
Biochemical cause
Source-
http://www.biologydiscussion.com/biotechnology/somaclonal-
variations/somaclonal-variations-basis-isolation-factors-and-
limitations/10712 - accessed on 11.4.18

9. Physiological Cause
 Exposure of culture to plant growth regulators.
 Culture conditions. ( Evan et al., 1984)

10. Genetic Cause
1. Change in chromosome number
 Euploidy: Changes chromosome Sets
 Aneuploidy: Changes in parts of chromosome
Sets
 Polyploidy: Organisms with more than two
chromosome sets
 Monoploidy: Organism with one
chromasomes set ( Lee and Ronald, 1988)
2. Change in chromosome structure
 Deletion
 Inversion
 Duplication
 Translocation ( Lee and Ronald, 1988)

11. 3. Gene Mutation
 Tansition
 Transversion
 Insertion
 Deletion
4. Plasma gene Mutation
5. Transposable element activation
( Lee and Ronald, 1988)
Genetic Cause

12. 6. DNA sequence
* Change in DNA
 Detection of altered fragment size by using
Restriction enzyme
 Change in Protein
 Loss or gain in protein band
 Alteration in level of specific protein
 Methylation of DNA
 Methylation inactivates transcription process.
( Lee and Ronald, 1988)
Genetic Cause

13. Factors affecting variation
 Selection propagule (cells, protoplasts, calli).
 Selection agent (toxin, herbicide, amino acid analogue).
 Technique used for selection.
 Duration of cell culture .(Jha and Ghosh, 2010)
 Growth hormone effects
 Stability of resistant substance.
 In vivo testing procedure.
 Ability for regeneration of plants.
 Genotype and explant source (Skirvin etal.1994)

14. Isolation of somaclonal variants
A number of selection systems are now being used to
select the variants.
A. Without in vitro technique:
 Unorganised callus and cells, grown in cultures for
various periods on a medium that contains no
selective agents, are induced to differentiate whole
plants.
 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

15. (Satyanarayana,2015)

16. Limitation of without in vitro
approch-
 There is no specific approach for isolation of
somaclones
 The appearance of a desired trait is purely by
chance.
 The procedure is time consuming and require
screening of many plants.

17. Isolation of somaclonal variants
B.With in vitro technique:
 Cell lines are screened from cultures by their ability to
survive in the presence of a substance in medium that
may be toxic or under condition 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).
 The plants resistant to the toxin are selected and grown
further by vegetative propagation or self-pollination.
 The subsequent generations are analysed for disease
resistant plants against the specific pathogenic

18. (Satyanarayana,2015)

19. Advantage of with in vitro
approch-
 There is specific selection for isolating a desired
trait.
 The procedure is less time consuming as
compared to without in vitro approach.

20. Detection of somaclonal variants
Different methods of selection and screening :
1. Analysis of morphological characters
 Qualitative characters: Plant height, maturity date,
flowering date and leaf size
 Quantitative characters: yield of flower, seeds and wax
contents in different plant parts
2. Variant detection by cytological Studies
 Staining of meristematic tissues like root tip, leaf tip with
feulgen and acetocarmine provide the number and
morphology of chromosomes. (Skirvin etal.1994)
3. Variant detection by DNA contents
 Cytophotometer detection of feulgen stained nuclei can
be used to measure the DNA contents (Skirvin etal.1994)

21. Detection of somaclonal variants
4. Variant detection by gel electrophoresis
 Change in concentration of enzymes, proteins
and hemical products like pigments, alkaloids and
amino acids can be detected by their
electrophoretic pattern
5. Detection of disease resistance variant
 Pathogen or toxin responsible for disease
resistance can be used as selection agent during
culture.
6. Detection of herbicide resistance variant
 Plantlets generated by the addition of herbicide to
the cell culture system can be used as herbicide

22. Detection of somaclonal variants
7. Detection of environmental stress tolerant variant
 Selection of high salt tolerant cell lines in tobacco.
 Selection of water-logging and drought resistance
cell lines in tomato.
 Selection of temperature stress tolerant in cell
lines in pear.
 Selection of mineral toxicities tolerant in sorghum
plant (mainly for aluminium toxicity) (Skirvin
etal.1994)

23.  Production of agronomically useful plants- ( Karp,1994)
In Table 46.3, somaclonal variations in a selected list of crops with
useful and improved morphological characters are given. The crops
include ric
 Resistance to diseases-
Somaclonal variations have largely contributed towards the
development of disease resistance in many crops without in vitro
selection and within vitro selection are respectively given in Tables
46.1 and 46.2.
 Resistance to abiotic stresses- ( Karp,1994)
i. Freezing tolerance e.g. wheat.
ii. Salt tolerance e.g., rice, maize, tobacco.
iii. Aluminium tolerance e.g., carrot, sorghum, tomato.
 Resistance to herbicides-
i. Tobacco resistant to glyphosate, sulfonylurea and picloram. ii.
Carrot resistant to glyphosate.
iii. Lotus resistant to 2, 4-dichlorophenoxy acetic acid (2, 2-D).
 Improved seed quality – ( Karp,1994)
A new variety of Lathyrus sativa seeds (Lathyrus Bio L 212) with a
Applications

24. Applications
(Satyanarayana,2015)

25. Limitations
 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 field trials
 Not suitable for complex agronomic traits like yield, quality
etc.
 May develop variants with pleiotropic effects which are not
true. (Karp,1994)

26.  Evans, D. A., W. R. Sharp, and Medina,H.,-"Somaclonal and gametoclonal
variation." American Journal of Botany (1984): Pp-759-774.
 Jha,T., and Ghosh, B., Somaclonal variation., Plant Tissue Culture Basic and
applied.(2010): Pp-200-219
 Karp, A. "Somaclonal variation as a tool for crop improvement." Euphytica 85.1-3 (1995): Pp-
295-302.
 Larkin, P., J., and Scowcroft,R.,. "Somaclonal variation—a novel source of variability from
cell cultures for plant improvement." Theoretical and applied Genetics 60.4 (1981): Pp-197-
214.
 Lee, M., and Ronald L. P. ,"The chromosomal basis of somaclonal variation." Annual Review
of Plant Physiology and Plant Molecular Biology 39.1 (1988): Pp-413-437.
 Skirvin, R., M., and Margaret N.,"Sources and frequency of somaclonal
variation." HortScience 29.11 (1994): Pp-1232-1237.
 Satyanarayana, U., Somaclonal variation, Biotechnology,9th edition,855, (2015): Pp-546-549
References

27.  http://www.agriinfo.in/default.aspx?page=topic&sup
erid=3&topicid2013- accessed on 11.4.18
 http://www.biologydiscussion.com/biotechnology/so
maclonal-variations/somaclonal-variations-basis-
isolation-factors-and-limitations/10712 - accessed
on 11.4.18
 http://www.biologydiscussion.com/biotechnology/so
maclonal-variations/applications-of-somaclonal-
variations/10716 - accessed on 11.4.18
References

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