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. 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
9. Use :
Recalcitrant seeds
Vegetatively propagated
Large seeds
In vitro Collection
Concern:
Security
Availability
cost
10. 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)
11. 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
12. 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)
Editor's Notes
I plan to go into more technical detail with tissue culture techniques than I do with some of the other molecular biology techniques. The reason is that there is much more breeder support available for molecular biology than for tissue culture techniques, and if you want to apply some of these techniques, you are much more likely to be on your own than you are if you want to apply some of the molecular biology techniques in your breeding program.
The only other source for genetic variation that I am aware of is polyploidy. As a breeder, you have to be aware of epigenetic variation because it can look like a good source to use for breeding, but since it’s not heritable, it can only be useful for vegetatively propagated crops. Sources for epigenetic variation include gene aplification, DNA methylation, and increased transposon activity. Since using somaclonal variation is the same as mutation breeding, I would like to take a look at mutation breeding in more detail.
