Ways of creating variations in plants

1. Ways of Creating Genetic
Variations in Plants.
Sarbesh D. Dangol
Nigde, Turkey.
December 21, 2015.
12/15/2015 1
Sarbesh D. Dangol, PhD Agricultural Genetic
Engineering.

2. Somaclonal Variation
• Variability frequently observed in cell cultures.
• Treatment with mutagenic agents not
inevitable.
• Variations originate among cells of somatic
origin.
• Millions of cells can be propagated in limited
space.
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Sarbesh D. Dangol, PhD Agricultural Genetic
Engineering.

3. • Beneficial genetic variations are utilized.
• Crop cultivars deficient in a particular trait
may be cultured and screened.
• Genetic stability required.
• Screening for stress resistance.
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Sarbesh D. Dangol, PhD Agricultural Genetic
Engineering.

4. Somaclonal Variation
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Sarbesh D. Dangol, PhD Agricultural Genetic
Engineering.

5. Deletion and Duplication
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Sarbesh D. Dangol, PhD Agricultural Genetic
Engineering.

6. Inversion and Translocation
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Sarbesh D. Dangol, PhD Agricultural Genetic
Engineering.

7. • Spontaneous point mutations, somatic crossing
over, transposable elements, euploidy, aneuploidy,
etc.
Other factors involved in
somaclonal variation
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Sarbesh D. Dangol, PhD Agricultural Genetic
Engineering.

8. Somatic Cell Hybridization
• Also called Somatic cell fusion or protoplast
fusion.
• Removal of cell wall by mechanical or chemical
enzymes.
• Nuclei fusion using PEG (Polyethylene glycol),
NaNO3, Ca2+ ions, polyvinyl alcohol, etc.
• Successful in potato, tobacco, alfalfa.
• Most difficult in cereal crops and grain legumes.
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Sarbesh D. Dangol, PhD Agricultural Genetic
Engineering.

9. Variation using
Somatic Cell
Hybridization
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Sarbesh D. Dangol, PhD Agricultural Genetic
Engineering.

10. Variation by
Cybridization
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Sarbesh D. Dangol, PhD Agricultural Genetic
Engineering.
•Cytoplasmic male sterility.
•Herbicide resistance.
•Antibiotic resistance.
•Chloroplast/mt-DNA fusion.

11. Variation by
Polyploidy induction
• Polyploidy permits greater expression of
genetic diversity.
• Unreduced gametes.
• Triploids/ Pentaploids are generally infertile.
• Used to genetically deseed certain plant
cultivars (eg-Triploid watermelon, banana).
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Sarbesh D. Dangol, PhD Agricultural Genetic
Engineering.

12. Polyploidy induction
• Use of colchicine (Alkaloid extracted from seeds of
Colchicum autumnale).
• Colchicine disrupts normal chromosomal division.
• Dissociates spindle preventing daughter
chromosomes’ migration to opposite poles, followed
by mitosis.
• Colchicine is applied to meristem regions of plants
by wetting with aqueous solution.
• Effective when applied to germinating seeds, to
roots or developing meristems.
12/15/2015 12
Sarbesh D. Dangol, PhD Agricultural Genetic
Engineering.

13. Artificially induced autoploids
• Autopolyploids (Autotetraploids) can be formed
from normal diploid plants. AA  AAAA
• Generally stockier and less fertile than diploid
parents.
• To be fully fertile, some mechanisms must
enforce bivalent chromosome pairing (natural
selection) for euploid gametes to occur.
• High seed production not necessary in
ornamentals, forage, grasses, vegetatively
propagated tuber crops.
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Sarbesh D. Dangol, PhD Agricultural Genetic
Engineering.

14. Artificially induced alloploids
• Natural: Wheat X Rye  Triticale.
• Ph1 allele in wheat is a suppressor gene of
homoeologus chromosome pairing to generate
tetraploids and hexaploids in wheats.
• Only bivalents can pair in meiosis. (In AABB, AA and BB
pairing, not AB pairing).
• Search wild germplasms with beneficial characters and
cross with cultivable crops.
• Beneficial only if produces viable seeds.
• Must be sufficiently normal and viable to reach
maturity.
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Sarbesh D. Dangol, PhD Agricultural Genetic
Engineering.

15. Bridging ploidy levels in interspecific
crosses
Purpose: For disease resistance, stress
resistance, improved traits.
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Sarbesh D. Dangol, PhD Agricultural Genetic
Engineering.

16. 12/15/2015 16
Sarbesh D. Dangol, PhD Agricultural Genetic
Engineering.

17.  In Triticosecale, hexaploids have better agronomic
traits than octoploid forms.
 More success when crossing closely related species at
low ploidy level.
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Sarbesh D. Dangol, PhD Agricultural Genetic
Engineering.

18. Variation using anther culture
• Colchicine treatment for doubled haploids.
• Completely homozygous diploid.
• Useful in mutation studies. Immediate display of recessive mutation.
• Selfing for several generations to obtain homozygosity not required.
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Sarbesh D. Dangol, PhD Agricultural Genetic
Engineering.

19. Variation using Agrobacterium
mediated transformation
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Sarbesh D. Dangol, PhD Agricultural Genetic
Engineering.

20. Mutational variation
• A sudden change in the heriditary material of
a cell.
• Involves deletions, rearrangements, loss of
chromosomes or duplication of chromosomes.
• Use of mutagenic agents such as X-rays, UV,
neutrons, gamma rays.
• Use of chemicals such as Ethyl methane
sulfonate (EMS) for less damage of cells.
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Sarbesh D. Dangol, PhD Agricultural Genetic
Engineering.

21. • Thank you. 
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Sarbesh D. Dangol, PhD Agricultural Genetic
Engineering.