Somaclonal Variation.....................pptx

1. Somaclonal Variation

2. SOMACLONAL VARIATION

3. INTRODUCTION
 “ Somaclonal variation” term was coined by Larkin and Scowcroft
(1981)
 According to Larkin and Scowcroft (1981), “Somaclonal variation is
the genetic variability which is regenerated during tissue
culture” or plant variants derived from any form of cell or tissue
cultures.
 Genetic variations in plants that have been produced by plant tissue
culture and can be detected as phenotypic traits.

4.  The phenomenon of high variability in individuals from plant cell
cultures or adventitious shoots is called Somaclonal variation.
 Somaclonal variation is the variation seen in plants that have been
produced by plant tissue culture.
 This may lead to desirable characteristics like increased pest resistance
etc. This work performed to achieve some of beneficial properties of
plants like disease resistance, fruit quality, stress resistance, nutritional
quality, yield improvement etc.

5.  Somaclonal variation – Occur as a result of genetic
heterogeneity in plant tissue culture (inside the plant or
explant) that changes can passes from one to another
generations.
This may be due to:
 Expression of chromosomal mosaicism or genetic
disorders
 Spontaneous mutations due to culture conditions or
Physiological causes.
 Variation in karyotype, isozyme characteristics and
morphology (number and structure of chromosome) in
somaclones may be observed.
 Regenerated plant with altered chromosomal changes
often show changes in leaf shapes, color, growth rate and

6. MECHANISMS OF SOMACLONAL VARIATION
 KARYOTYPIC CHANGE
 Several plants alter their chromosome number in culture. Gross
karyotypic alterations have been observed in tissue cultured plant cells.
 Certain karyotypic changes such as aneuploidy or polyploidy is
responsible for the generations of clones.
 CHROMOSOMAL REARRANGEMENT:
 It has been elusive that several cryptic chromosomal rearrangements in
tissue culture conditions are responsible for somaclonal variation.
 Tissue culture derived from Barley plants show breakage, reunion and
translocations in their chromosomes.

7.  The same kind of irregularities
such as breaks, acentric and
centric fragments, ring
chromosomes and micronuclei
was noticed in the mixoploidy
garlic plants.
 This cryptic changes associated
with chromosomal
rearrangements not only result in
the loss of genes and their

8.  NUCLEOTIDE POOL IMBALANCE
 Imbalance is the nucleotide reserve may have serious
implications on nuclear DNA as well as organellar DNA
mutation.
 In addition, wide array of anomalies like chromosomal
aberrations, aneuploidy and sister chromatid exchange
result high degree of genetic variations.
 Plant tissue and cell culture provides ideal conditions for
the induction of imbalance nucleotide reserve pool during
serially transfer from depleted to fresh medium.
 This means that media components gets completely
depleted towards the end of subculture. As a
consequence, metabolic process fluctuates and may be
responsible for somaclonal variation.

9.  SOMATIC GENE REARRANGEMENT
 Somatic gene arrangements have been recorded in animal system, in
which mouse embryonic cells to plasma cells involves chromosomal
gene arrangements.
 It would also be possible that somatic gene arrangements will also occur
in higher plants. If so then the regenerated plants form somatic cells by
culture encourages somatic gene rearrangements seen in the new
germline.

10. TYPES OF SOMACLONAL VARIATION

11. CAUSES OF SOMACLONAL VARIATION
PHYSIOLOGICAL CAUSE

12. GENETIC CAUSE

14. BIOCHEMICAL CAUSE

15. Isolation of Somaclonal Variation
1)Generation of
Somaclonal variation
without in-vitro
Selection.

16. WITHOUT IN-VITRO TECHNIQUE
 Unorganized callus and cells, grown in cultures for various periods on a medium
that contain no selective agents, are induced to differentiate whole plants.
 An explant is cultivated on a suitable medium, supplemented with growth
regulators.
 The unorganized callus and cells do not contain any selective agent.
 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 varieties.
LIMITATIONS
1. Time consuming procedure
2. Require screening in many plants.
3. Appearance of desired traits are purely by chance.

17. 2) Generation of
Somaclonal Variation
with in-vitro
selection.

18. WITH IN-VITRO TECHNIQUE
 Cell lines are analyzed from plant cultures for their capability to survive in the presence
of a toxic substance in medium or under environmental stress conditions
 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.
 The plants resistant to the toxin are selected and grown further by vegetative
propagation .
 The subsequent generations are analyzed for disease resistant plants against the
specific pathogenic organism.
Advantages of With in-vitro Selection
 Specific approach for isolation of desired trait
 Less time consuming procedure as compared without
in-vitro approach

19. Applications of Somaclonal 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
Examples: Sugarcane: Selections for higher yield and disease resistance.
Potatoes: Yield and disease resistance
Paulownia: selection for leaf variegation.

20. 1) Production of agronomically useful plants (Novel Variants)
As a result of somaclonal variations, several novel variants of existing crops have been developed
e.g. An improved scented Geranium variety named ‘ Velvet Rose’, Pure thorn-less blackberries
etc.

21. 2) Production of Abiotic stress
resistance variety:
 Somaclonal variation has resulted in several
interesting biochemical mutants, which are being
successfully used in plant metabolic pathway studies,
i.e. amino acid and secondary metabolic pathways.
 Investigations have shown that level of free amino
acids, especially proline, increases during cold
hardening.
 In vitro selection has also been used to obtain plants
with increased acid soil, salt, aluminium and herbicide
resistance.

22. COLD TOLERANCE
 Lazar et.al., 1988 developed
somaclonal variants for freezing
tolerance in Norstar winter wheat. A
significant positive correlation
between proline level and frost
tolerance has been found in a broad
spectrum of genotypes.
 In vitro selection and regeneration
of hydroxyproline resistant lines of
winter wheat with increased frost

23. SALT TOLERANCE
 Plant tissue culture techniques have been
successfully used to obtain salt tolerant cell
lines or variants in several plant species,
tobacco, rice, maize, Brassica, Solanum
nigrum, Sorghum etc.
 Mandal et.al., 1999 developed a salt tolerant
somaclone BTS24 from indigenous rice
cultivar pokkali.

24. ALUMINIUM TOLERANCE
 In recent years, considerable research has been focused on the
understanding of physiological, genetic and molecular processes that
lead to aluminium tolerance.
 Aluminium toxicity during in-vitro selection in rice by making several
modifications in the media.( Low pH, low phosphate and calcium
concentrations.)
DROUGHT TOLERANCE
 Wang et al., 1993 used in vitro selection technique for generation of
somaclonal variants for Russian wheat aphid (Diuraphis noxia) in wheat.
 Variant of Bermuda grass (Cynodon dactylon) called Brazos R-3 with
increased resistance to fail armyworm.

25. 3) Disease Resistance
 Development of disease
resistance in many crops:
Rice, Wheat, Maize,
Sugarcane, Tobacco, Apple,
Tomato etc..
 Selected crops somaclonal
variants, with increasing
disease resistance developed,
without in-vitro selection are
respectively.
 Resistance first reported in
Sugarcane for Eye spot

26. 4) HERBICIDE RESISTANCE
 Through in-vitro selection several cell lines resistant to herbicides have
been isolated and few have been regenerated into complete plants.
 Tobacco resistant to Glyphosate, Sulfonylurea and Picloram
 Carrot resistant to Glyphosate
 Lotus resistant to 2,4 dichlorophenoxyacetic acid(2,4D)

27. 5) Improved Seed Quality
 Recently, a variety Bio L 212 of Lathyrus sativa has
been identified for cultivation in central India.
 This has been developed through somaclonal
variation and has low ODAP (𝛃-N-oxalyl-2-𝛂, 𝜷
diamino propionic acid), a neurotoxin, indication the
potential of somaclonal variation for the development
of varieties with improved seed quality

28. Advantages and Disadvantages of Somaclonal variation

29. Reference:-
 Evans D.A., Sharp W.R., Medina H. “Somaclonal
and Gametoclonal Variation” Am J Botany (1984)
759-774
 Satyanarayana U. “Somaclonal Variation,
Biotechnology, 9th Ed,(2015) 855: 546-549
 Larkin P.J., Margaret N. “Sources and Frequency of
Somaclonal variation”HortiSci 29.11 (1994) 1232-
1237