The document discusses various applications of plant tissue culture including the development of superior cultivars through somaclonal variation, embryo rescue, anther and pollen cultures, and protoplast fusion. It also describes micropropagation in detail, including its features, steps, and advantages over conventional propagation methods. Additionally, it covers somatic hybridization and the process of protoplast isolation, fusion, selection of hybrid cells, and regeneration of hybrid plants.

1. Plant Tissue Culture
Application

2. Development of
superior cultivars
Germplasm storage
Somaclonal variation
Embryo rescue
Ovule and ovary cultures
Anther and pollen cultures
 Callus and protoplast culture
Protoplasmic fusion
In vitro screening
 Multiplication

3. Tissue Culture Applications
Micropropagation
Germplasm preservation
Somaclonal variation
Haploid & dihaploid production
In vitro hybridization – protoplast fusion

4. Micropropagation

5. Features of Micropropagation
• Clonal reproduction
– Way of maintaining heterozygozity
• Multiplication stage can be recycled many times to
produce an unlimited number of clones
– Routinely used commercially for many ornamental species,
some vegetatively propagated crops
• Easy to manipulate production cycles
– Not limited by field seasons/environmental influences
• Disease-free plants can be produced
– Has been used to eliminate viruses from donor plants

6. Microcutting propagation
• It involves the production of shoots from pre-existing
meristems only.
• Requires breaking apical dominance
• This is a specialized form of organogenesis

7. Steps of Micropropagation
• Stage 0 – Selection & preparation of the mother plant
– sterilization of the plant tissue takes place
• Stage I - Initiation of culture
– explant placed into growth media
• Stage II - Multiplication
– explant transferred to shoot media; shoots can be constantly
divided
• Stage III - Rooting
– explant transferred to root media
• Stage IV - Transfer to soil
– explant returned to soil; hardened off

8. Conventional Micropropagation
Duration: 6 years 2 years
Labor: Dig & replant every 2 years; Subculture every 4 weeks;
unskilled (Inexpensive) skilled (more expensive)
Space: More, but less expensive (field) Less, but more expensive
(laboratory)
Required to
prevent viral Screening, fumigation, spraying None
infection:
COMPARISON OF CONVENTIONAL &
MICROPROPAGATION OF VIRUS
INDEXED REGISTERED RED
RASPBERRIES

9. Ways to eliminate viruses
 Heat treatment.
Plants grow faster than viruses at high temperatures.
 Meristemming.
Viruses are transported from cell to cell through
plasmodesmata and through the vascular tissue. Apical
meristem often free of viruses. Trade off between infection
and survival.
 Not all cells in the plant are infected.
Adventitious shoots formed from single cells can give virus-
free shoots.

10. Elimination of viruses
Plant from the field
Pre-growth in the greenhouse
‘Virus-free’ Plants
Heat treatment
35o
C / months
Active
growth
Meristem culture
Micropropagation cycle
Virus testing
Adventitious
Shoot
formation

11. Indirect Somatic Embryogenesis
Explant → Callus Embryogenic → Maturation → Germination
1.Callus induction
2. Embryogenic callus development
3.Maturation
4.Germination

12. Induction
• Auxins required for induction
–Proembryogenic masses form
–2,4-D most used
–NAA, dicamba also used

13. Development
Auxin must be removed for embryo development
Continued use of auxin inhibits embryogenesis
Stages are similar to those of zygotic embryogenesis
– Globular
– Heart
– Torpedo
– Cotyledonary
– Germination (conversion)

14. Maturation
• Require complete maturation with apical
meristem, radicle, and cotyledons
• Often obtain repetitive embryony
• Storage protein production necessary
• Often require ABA for complete maturation
• ABA often required for normal embryo
morphology
– Fasciation
– Precocious germination

15. Germination
• May only obtain 3-5% germination
• Sucrose (10%), mannitol (4%) may be required
• Drying (desiccation)
– ABA levels decrease
– Woody plants
– Final moisture content 10-40%
• Chilling
– Decreases ABA levels
– Woody plants

16.  In situ : Conservation in ‘normal’ habitat
–rain forests, gardens, farms
 Ex Situ :
–Field collection, Botanical gardens
–Seed collections
–In vitro collection: Extension of micropropagation techniques
•Normal growth (short term storage)
•Slow growth (medium term storage)
•Cryopreservation (long term storage
 DNA Banks
Plant germplasm preservation

17. Use :
 Recalcitrant seeds
 Vegetatively propagated
 Large seeds
In vitro Collection
Concern:
 Security
Availability
cost

18.  Use of immature zygotic embryos
(not for vegetatively propagated species)
 Addition of inhibitors or retardants
 Manipulating storage temperature and light
 Mineral oil overlay
 Reduced oxygen tension
 Defoliation of shoots
Ways to achieve slow growth

19. Conservation of plant germplasm
• Vegetatively propagated species (root and tubers, ornamental, fruit trees)
• Recalcitrant seed species (Howea, coconut, coffee)
Conservation of tissue with specific characteristics
• Medicinal and alcohol producing cell lines
• Genetically transformed tissues
• Transformation/Mutagenesis competent tissues (ECSs)
Eradication of viruses (Banana, Plum)
Conservation of plant pathogens (fungi, nematodes)
Cryopreservation
Storage of living tissues at ultra-low temperatures (-196°C)

21. Cryopreservation Steps
 Selection
 Excision of plant tissues or organs
 Culture of source material
 Select healthy cultures
 Apply cryo-protectants
 Pre-growth treatments
 Cooling/freezing
 Storage
 Warming & thawing
 Recovery growth
 Viability testing
 Post-thawing

22. Cryopreservation Requirements
• Preculturing
– Usually a rapid growth rate to create cells with small vacuoles
and low water content
• Cryoprotection
– Cryoprotectant (Glycerol, DMSO/dimetil sulfoksida, PEG)
to protect against ice damage and alter the form of ice crystals
• Freezing
– The most critical phase; one of two methods:
• Slow freezing allows for cytoplasmic dehydration
• Quick freezing results in fast intercellular freezing with little
dehydration

23. Cryopreservation Requirements
• Storage
– Usually in liquid nitrogen (-196o
C) to avoid changes in ice
crystals that occur above -100o
C
• Thawing
– Usually rapid thawing to avoid damage from ice crystal
growth
• Recovery
– Thawed cells must be washed of cryo-protectants and nursed
back to normal growth
– Avoid callus production to maintain genetic stability

25. Somaclonal Variation
 Variation found in somatic cells dividing mitotically in culture
 A general phenomenon of all plant regeneration systems that
involve a callus phase
Some mechanisms:
 Karyotipic alteration
 Sequence variation
 Variation in DNA Methylation
Two general types of Somaclonal Variation:
– Heritable, genetic changes (alter the DNA)
– Stable, but non-heritable changes (alter gene expression,
epigenetic)

26. Epigenetic
the study of gene regulation that does not involve making changes
to the SEQUENCE of the DNA, but rather to the actual BASES
within the nucleotides and to the HISTONES
The three main mechanisms for regulation are:
 CpG island methylation (…
meCGmeCGmeCGmeCGmeCGmeCGmeCGmeCG…)
 acetylation and methylation of histone H3
 the production of antisense RNA

27. Somaclonal Breeding Procedures
• Use plant cultures as starting material
– Idea is to target single cells in multi-cellular culture
– Usually suspension culture, but callus culture can
work (want as much contact with selective agent as
possible)
– Optional: apply physical or chemical mutagen
• Apply selection pressure to culture
– Target: very high kill rate, you want very few cells to
survive, so long as selection is effective
• Regenerate whole plants from surviving cells

28. Requirements for Somaclonal Breeding
• Effective screening procedure
– Most mutations are deleterious
• With fruit fly, the ratio is ~800:1 deleterious to beneficial
– Most mutations are recessive
• Must screen M2 or later generations
• Consider using heterozygous plants?
– But some say you should use homozygous plants to be sure effect is mutation
and not natural variation
• Haploid plants seem a reasonable alternative if possible
– Very large populations are required to identify desired mutation:
• Can you afford to identify marginal traits with replicates & statistics?
Estimate: ~10,000 plants for single gene mutant
• Clear Objective
– Can’t expect to just plant things out and see what happens; relates
to having an effective screen
– This may be why so many early experiments failed

30. Embryo Culture Uses
• Rescuing interspecific and intergeneric hybrids
– wide hybrids often suffer from early spontaneous abortion
– cause is embryo-endosperm failure
– Gossypium, Brassica, Linum, Lilium
• Production of monoploids
– useful for obtaining "haploids" of barley, wheat, other cereals
– the barley system uses Hordeum bulbosum as a pollen parent

31. Bulbosum Method
Hordeum
vulgare
Barley
2n = 2X = 14
Hordeum
bulbosum
Wild relative
2n = 2X = 14
Haploid Barley
2n = X = 7
H. Bulbosum
chromosomes
eliminated
X
Embryo Rescue
↓
• This was once more efficient than microspore culture in creating
haploid barley
• Now, with an improved culture media (sucrose replaced by
maltose), microspore culture is much more efficient (~2000
plants per 100 anthers)

32. Bulbosum technique
H. vulgare is the seed parent
zygote develops into an embryo with elimination of HB
chromosomes
eventually, only HV chromosomes are left
embryo is "rescued“ to avoid abortion
Excision of the immature embryo:
 Hand pollination of freshly opened flowers
 Surface sterilization – EtOH on enclosing structures
 Dissection – dissecting under microscope necessary
 Plating on solid medium – slanted media are often used to
avoid condensation

33. Culture Medium
– Mineral salts – K, Ca, N most important
– Carbohydrate and osmotic pressure
– Amino acids
– Plant growth regulators

34. Culture Medium
–Carbohydrate and osmotic pressure
» 2% sucrose works well for mature embryos
» 8-12% for immature embryos
» transfer to progressively lower levels as embryo grows
» alternative to high sucrose – auxin & cyt PGRs
– amino acids
» reduced N is often helpful
» up to 10 amino acids can be added to replace N salts, incl.
glutamine, alanine, arginine, aspartic acid, etc.
» requires filter-sterilizing a portion of the medium

35. – natural plant extracts
» coconut milk (liquid endosperm of coconut)
» enhanced growth attributed to undefined hormonal factors
and/or organic compounds
» others – extracts of dates, bananas, milk, tomato juice
– PGRs
» globular embryos – require low conc. of auxin and cytokinin
» heart-stage and later – usually none required
» GA and ABA regulate "precocious germination“
» GA promotes, ABA suppresses
Culture Medium

36. “Wide” crossing of wheat and rye
requires embryo rescue and chemical
treatment to double the number of
chromosomes.
Triticale

37. Haploid Plant Production
 Embryo rescue of interspecific
crosses
– Creation of alloploids
 Anther culture/Microspore
culture
– Culturing of Anthers or
Pollen grains (microspores)
– Derive a mature plant from a
single microspore
 Ovule culture
– Culturing of unfertilized
ovules (macrospores)

38. Specific Examples of DH uses
• Evaluate fixed progeny from an F1
– Can evaluate for recessive & quantitative traits
– Requires very large dihaploid population, since no prior selection
– May be effective if you can screen some qualitative traits early
• For creating permanent F2 family for molecular marker
development
• For fixing inbred lines (novel use?)
– Create a few dihaploid plants from a new inbred prior to going to
Foundation Seed (allows you to uncover unseen off-types)
• For eliminating inbreeding depression (theoretical)
– If you can select against deleterious genes in culture, and screen
very large populations, you may be able to eliminate or reduce
inbreeding depression
– e.g.: inbreeding depression has been reduced to manageable level
in maize through about 50+ years of breeding; this may reduce
that time to a few years for a crop like onion or alfalfa

39. Somatic Hybridization
Development of hybrid plants through the fusion of somatic
protoplasts of two different plant species/varieties

40. Somatic hybridization technique
1. isolation of protoplast1. isolation of protoplast
2. Fusion of the protoplasts of desired species/varieties2. Fusion of the protoplasts of desired species/varieties
3. Identification and Selection of somatic hybrid cells3. Identification and Selection of somatic hybrid cells
4. Culture of the hybrid cells4. Culture of the hybrid cells
5. Regeneration of hybrid plants5. Regeneration of hybrid plants

41. Isolation of Protoplast
(Separartion of protoplasts from plant tissue))
1. Mechanical Method 2. Enzymatic Method

42. Mechanical Method
Plant Tissue
Collection of protoplasm
Cells Plasmolysis
Microscope Observation of cells
Cutting cell wall with knife
Release of protoplasm

43. Mechanical Method
Used for vacuolated cells like onion bulb scale,
radish and beet root tissues
Low yield of protoplast
Laborious and tedious process
Low protoplast viability

44. Enzymatic Method
Leaf sterlization, removal of
epidermis
Plasmolysed
cells
Plasmolysed
cells
Pectinase +cellulase Pectinase
Protoplasm released
Release of
isolated cells
cellulase
Protoplasm
released
Isolated
Protoplasm

45. Enzymatic Method
Used for variety of tissues and organs including
leaves, petioles, fruits, roots, coleoptiles, hypocotyls,
stem, shoot apices, embryo microspores
 Mesophyll tissue - most suitable source
 High yield of protoplast
 Easy to perform
 More protoplast viability

46. Protoplast FusionProtoplast Fusion
(Fusion of protoplasts of two different genomes(Fusion of protoplasts of two different genomes))
1. Spontaneous Fusion 2. Induced Fusion
Intraspecific Intergeneric Electrofusion
Mechanical
Fusion
Chemofusion

47. Uses for Protoplast Fusion
Combine two complete genomes
– Another way to create allopolyploids
In vitro fertilization
Partial genome transfer
– Exchange single or few traits between species
– May or may not require ionizing radiation
Genetic engineering
– Micro-injection, electroporation, Agrobacterium
Transfer of organelles
– Unique to protoplast fusion
– The transfer of mitochondria and/or chloroplasts between
species

48. Spontaneous Fusion
• Protoplast fuse spontaneously during isolation
process mainly due to physical contact
• Intraspecific produce homokaryones
• Intergeneric have no importance

49. Induced Fusion
• Types of fusogens
• PEG
• NaNo3
• Ca 2+
ions
• Polyvinyl alcohol
Chemofusion- fusion induced by chemicals

50. Induced Fusion
• Mechanical Fusion- Physical fusion of protoplasts
under microscope by using micromanipulator and
perfusion micropipette
• Electrofusion- Fusion induced by electrical stimulation
• Fusion of protoplasts is induced by the application of high strength
electric field (100kv m-1
) for few microsecond

51. Possible Result of Fusion of Two
Genetically Different Protoplasts
= chloroplast
= mitochondria
= nucleus
Fusion
heterokaryon
cybrid cybridhybrid
hybrid

52. Identifying Desired Fusions
• Complementation selection
– Can be done if each parent has a different selectable marker (e.g.
antibiotic or herbicide resistance), then the fusion product
should have both markers
• Fluorescence-activated cell sorters
– First label cells with different fluorescent markers; fusion
product should have both markers
• Mechanical isolation
– Tedious, but often works when you start with different cell types
• Mass culture
– Basically, no selection; just regenerate everything and then screen
for desired traits

53. Advantages of somatic
hybridization
• Production of novel interspecific and intergenic hybrid
– Pomato (Hybrid of potato and tomato)
• Production of fertile diploids and polypoids from sexually
sterile haploids, triploids and aneuploids
• Transfer gene for disease resistance, abiotic stress
resistance, herbicide resistance and many other quality
characters
• Production of heterozygous lines in the single species
which cannot be propagated by vegetative means
• Studies on the fate of plasma genes
• Production of unique hybrids of nucleus and cytoplasm

54. Problem and Limitation of
Somatic Hybridization
1. Application of protoplast technology requires efficient plant
regeneration system.
2. The lack of an efficient selection method for fused product is
sometimes a major problem.
3. The end-product after somatic hybridization is often unbalanced.
4. Development of chimaeric calluses in place of hybrids.
5. Somatic hybridization of two diploids leads to the formation of an
amphiploids which is generally unfavorable.
6. Regeneration products after somatic hybridization are often variable.
7. It is never certain that a particular characteristic will be expressed.
8. Genetic stability.
9. Sexual reproduction of somatic hybrids.
10. Inter generic recombination.

55. TYPICAL SUSPENSION PROTOPLAST
+ LEAF PROTOPLAST PEG-INDUCED
FUSION

57. NEW SOMATIC HYBRID PLANT

58. True in vitro fertilization
 Using single egg and sperm cells and fusing them
electrically
 Fusion products were cultured individually in 'Millicell'
inserts in a layer of feeder cells
 The resulting embryo was cultured to produce a fertile
plant
A procedure that involves retrieval of eggs and
sperm from the male and female and placing them
together in a laboratory dish to facilitate
fertilization

60. Requirements for plant genetic
transformation
• Trait that is encoded by a single gene
• A means of driving expression of the gene in
plant cells (Promoters and terminators)
• Means of putting the gene into a cell (Vector)
• A means of selecting for transformants
• Means of getting a whole plant back from the
single transformed cell (Regeneration)