Embed Size (px)
Citation preview
Sarbesh D. Dangol, PhD Agricultural Genetic Engineering.
1
Ways of Creating Genetic Variations in Plants.
Sarbesh D. DangolNigde, Turkey.
December 21, 2015.
12/15/2015
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.
12/15/2015
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.
12/15/2015
Sarbesh D. Dangol, PhD Agricultural Genetic Engineering.
4
Somaclonal Variation
12/15/2015
Sarbesh D. Dangol, PhD Agricultural Genetic Engineering.
5
Deletion and Duplication
12/15/2015
Sarbesh D. Dangol, PhD Agricultural Genetic Engineering.
6
Inversion and Translocation
12/15/2015
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
12/15/2015
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.
12/15/2015
9
Variation using Somatic Cell
Hybridization
12/15/2015
Sarbesh D. Dangol, PhD Agricultural Genetic Engineering.
10
Variation byCybridization
12/15/2015
Sarbesh D. Dangol, PhD Agricultural Genetic Engineering.
•Cytoplasmic male sterility.•Herbicide resistance.•Antibiotic resistance.
•Chloroplast/mt-DNA fusion.
Sarbesh D. Dangol, PhD Agricultural Genetic Engineering.
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).
12/15/2015
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
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.
12/15/2015
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.
12/15/2015
Sarbesh D. Dangol, PhD Agricultural Genetic Engineering.
15
Bridging ploidy levels in interspecific crosses
Purpose: For disease resistance, stress resistance, improved traits.
12/15/2015
Sarbesh D. Dangol, PhD Agricultural Genetic Engineering.
1612/15/2015
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.
12/15/2015
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.
12/15/2015
Sarbesh D. Dangol, PhD Agricultural Genetic Engineering.
19
Variation using Agrobacterium mediated transformation
12/15/2015
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.
12/15/2015
Sarbesh D. Dangol, PhD Agricultural Genetic Engineering.
21
• Thank you.
12/15/2015
