Soma clonal and gametoclonal variation in crop improvement

1. SOMACLONAL VARIATION FOR CROP
IMPROVEMENT
SUBMITTED BY- MONALISA MATHAN
M.SC. BOTANY 1ST YEAR
ROLL- 20MSLSPS34
SUBMITTED TO- DR. VINAY K. YADAV
ASSISTANT PROFESSOR
CENTRAL UNIVERSITY OF PUNJAB, BATHINDA
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2. CONTENTS:
• Introduction
• Features
• Mechanism
• Cause of variation
• Factors affecting production of variants
• Isolation and Detection of somaclonal variants
• Application
• Disadvantages
• Conclusion
• References
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3. INTRODUCTION:
• Soma- somatic cells and clones- generations
• Somaclonal variation- the genetic and phenotypic
variation obtained from a single donor clone
among clonally propagated plants.
• The term Somaclonal Variation was first proposed
by Larkin and Scrowcroft in 1981. (Larkin,1981)
• According to Larkin and Scowcroft, “Somaclonal
variation is termed as the genetic variability which
is regenerated during tissue culture or plant
variants derived from any form of cell or tissue
cultures”. (Larkin,1981).
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4. • The recovery of genetic changes in plants generated from somatic cells provide
opportunities to give rise to natural variability and to use this variation for development
of new varieties for plenty of good purposes. (Larkin,1981)
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Figure showing a basic procedure to produce somaclonal variants

5. FEATURES:
• Calliclone(clones of callus),mericlone (clones of meristem) and protoclone (clones of
Protoplast) are obtained also.(Jha and Ghosh, 2010)
• Even after plantation into the field, heritable mutation is observed in plant population.
NOMENCLATURE OF SOMACLONES:
• The somaclones generated from tissue culture directly are termed as Ro or R plants.
• R1,R2, R3,R4 etc. plants are the subsequent generations.
• Some other workers use another criterion of nomenclature(Ro=SC1) and SC2,SC3,SC4
for subsequent generations.
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6. MECHANISM:
• Somaclonal variation occur as a result of genetic heterogeneity in plant tissue
culture.
6
A flow chart showing the steps involved to produce somaclonal variants
Source-
(https://www.researchgate.net/profile/PoojaManchanda/publication/325926985/figure/fig1/AS:643834597896192@1530513538202/Sc
heme-for-induction-and-selection-of-somaclonal-variation-in-sugarcane.png)

7. 7
Source-https://prod-
illustrations.s3.amazonaws.com/public/templates/5f1758d706055900ac53e3f4/thumbnail/V2_1595365591199_a86d4
0c5-729a-4b16-9317-db3f5bae302b_public.png)

8. KINDS OF VARIATION:
• Epigenetic change
• Physiological change
• Cytogenetic/ genetic change
• Biochemical change
• Phenotypic change
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9. Epigenetic change ( non-heritable variations):
• Epigenetic control of gene expression- somatically or meiotically heritable alteration in
gene expression that is potentially reversible and is not due to sequence modification.
• The consequences are not expressed in sexual progenies.
Physiological Cause :
• Exposure of culture media to plant hormones- that affects the growth of the plant
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10. Genetic Cause ( heritable variation):
I. Change in chromosome number
• Euploidy: gain or loss of a set of chromosomes
• Aneuploidy: when 1 or more chromosomes are add
• Polyploidy: gain or loss of an entire genome of an organism
II. Change in chromosome structure
• Deletion
• Inversion
• Duplication
• Translocation ( Lee and Ronald, 1988)
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11. III. Gene Mutation:
• Transition
• Transversion
• Insertion
• Deletion
IV. By Cytoplasmic genetic changes and plasma gene mutation:
V. Activation of transposable genetic element:
• Genomic changes in maize line and mutations in tobacco are caused by the
activation of transposable elements.
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12. VI. DNA sequence
 Due to certain changes in DNA:
• By using Restriction enzyme, the altered fragment is detected.
 Caused by changes in Protein
• Loss or gain of additional sequence in protein band
• Specific protein alteration
 Caused by DNA methylation:
• Methylation inactivates transcription process. ( Lee and Ronald, 1988)
VII. Mitotic crossing over:
• Mitotic crossing over is caused by symmetric or asymmetric recombination in
regenerated plants.
Phenotypic changes:
• The change is caused by the effect of environmental factors on the genotypes of
desired plant specimen.
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13. FACTORS AFFECTING VARIATION:
• Selection of propagule types (cells, protoplasts, calli).
• Selection agent for variation(toxin, herbicide, amino acid analogue).
• Kind of tools or technique used for selection.
• Duration of cell culture to regenerate plant specimen .(Jha and Ghosh, 2010)
• Growth hormone effects – auxin and cytokinin ratio greatly matters for
regeneration.
• Stability of resistant substance- durability of the substance
• Type of genotype and explant source (Skirvin etal.1994)
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14. DETECTION OF SOMACLONAL VARIANTS:
Different methods of selection and screening :
morphological characters of plant specimen :
• Qualitative characters: Plant height, maturity date,
flowering date and leaf size
• Quantitative characters: yield of flower, seeds and wax
contents in different plant parts
Detecting variant by means of cytological Studies:
• The number and morphology of chromosomes are
detected by staining meristematic tissues like root tip,
leaf tip with feulgen and acetocarmine dyes. (Skirvin
etal.1994)
Isolating variants on the basis of DNA contents:
• Measurement of the DNA contents is carried out by
cytophotometer.
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cells stained by
acetocarmine
DNA content stained
by feulgen dye

15. By using the technique of gel electrophoresis
Detection of disease resistance variant
• Pathogen or toxin responsible for disease resistance can be used as selection agent
during culture.
Detection of herbicide resistance variant:
• Resistance to herbicides-
i. Tobacco is resistant to glyphosate, sulfonylurea and picloram.
ii. Carrot is resistant to glyphosate
iii. Lotus is resistant to 2, 4-dichlorophenoxy acetic acid (2, 2-D)
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Gel electrophoresis to extract DNA

16. Detection of environmental stress tolerant variant:
• Discovery of high salt tolerant cell lines in tobacco.
• water-logging and drought resistance cell lines identification in tomato.
• temperature stress tolerant in cell lines discovery in pear.
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.
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Detection of disease resistant plant

17. APPLICATION OF SOMACLONAL VARIATION:
I. Novel variants:
• SCV sometimes leads to form some diverse novel variants having excellent
agronomic uses.
• Ex- development of an improved Geranium variety named “velvet rose”, production
of pure throne less black berries, discovery of Hasuyume- a protoplast derived rice
cultivar
II. Somaclonal variation and disease resistance:
• The 1st reported resistant spp. was sugarcane for eye spot disease
(Helminthosporium sacchari), downy mildew( Sclerospora sacchari).
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18. III. Somaclonal variation and abiotic stress resistance:
• Interesting biochemical mutants are evolved successfully which are used in plant
metabolic studies- secondary metabolic pathway and amino acid pathway.
IV. Salt tolerance and Aluminium tolerance:
• Mandal(1999) had developed a salt tolerant somaclone BTS24 from indigenous rice
cultivar named as Pokkali.
• By exposing excess ionic aluminium in form of aluminium chloride, the aluminium
tolerant somaclonal variants were selected.
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19. V. Herbicide resistance and Insect resistance:
• The somaclonal variants for Russian wheat aphid ( Deuraphis noxia) in wheat
was demonstrated by Zemetra(1993). An extract from aphid was exposed to
‘Stephens’(the calli from susceptible wheat cultivar).
VI. Seed quality:
• E.g.- a variety Bio L-212 of Lathyrus sativa- has improved seed quality
V. Alien gene introgression:
• Introgression of alien gene helps to widen crop germplasm base.
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20. HOW TO INCREASE SOMACLONAL VARIATION?
• The selected somaclones for genetic stability are tested and subsequent generations
are cultured by regenerating large number of plant specimen from long-term cultures.
• New cultivars are designed by growth and multiplication of genetically stable
somaclones.
• Several cycles of callus and suspension cultures are performed on regular interval.
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21. IS SOMACLONAL VARIATION SUCCESSFUL EQUALLY IN ALL THE CROP PLANTS?
• The method is used in coffee plant shortening programmes. It requires min. 20-25 years
to release a new variety.
• The general conclusion is somaclonal variation is successful in crops having limited
genetic system and narrow genetic base.
DISADVANTAGES:
• The variation is often uncontrollable and unpredictable – important traits may get lost.
• The frequency of variation is variable and not stable all the time – it might create new
variant progenies.
• Sometimes the variation is not implemented for agronomic traits like- quality, yield etc.
• Extended and extensive field trials are required.
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22. CONCLUSION:
• The complex phenomenon of somaclonal
variation occurs because of the multiplicity of
cellular and genetic mechanisms. The
genomic changes help in differentiation and
de-differentiation of cells.
• Salt tolerant, insect resistant, herbicide
resistance like plant varieties are designed by
crop breeders to improve yielding quality.
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23. REFERENCES:
• Abreu IS, Carvalho CR, Clarindo WR (2014) Massal induction of Carica papaya L.
‘Golden’ somatic embryos and somaclone screening by flow cytometry and
cytogenetic analysis. Cytologia 79(4):475–484 Article Google Scholar
• Afrasiab H, Iqbal J (2010) In vitro techniques and mutagenesis for the genetic
improvement of potato cvs. Desiree and Diamant. Pak J Bot 42:1629–1637 Google
Scholar
• Ahloowalia BS (1992) In vitro radiation induced mutants in Chrysanthemum. Mutat
Breed Newsl Google Scholar
• Alizadeh M, Singh SK, Jhang T, Sharma TR (2008) Inter simple sequence repeat
analysis to confirm genetic stability of micropropagated plantlets in three grape
(Vitis spp) rootstock genotypes. J Plant Biochem Biotechnology 17:77–80
• Deng ZN, Gentile A, Domina F, Nicolosi E, Tribulato E (1995) Selecting lemon
protoplasts for insensitivity to Phoma tracheiphila toxin and regenerating tolerant
plants. J Am Soc Hortic Sci 120:902–905 Google Scholar
• Devanand PS, Chen J, Henny RJ, Chao CCT (2004) Assessment of genetic
relationships among Philodendron cultivars using AFLP markers. J Am Soc Hortic Sci
129:690–697
• Grosser JW, Gmitter FG Jr, Chandler JL (1996) Somaclonal variation in sweet
orange—a tool for cultivar improvement. In: Proceedings of International Society of
Citriculture VIII Congress, Sun City, South Africa, pp 203–206
• Hwang SC, Ko WH (2004) Cavendish banana cultivars resistant to Fusarium wilt acquired
through somaclonal variation in Taiwan. Plant Dis 88:580–588
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THANK YOU
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