PLANT TISSUE CULTURE

BY SREEREMYA

Types of Tissue Culture

• The types of tissue culture can be grouped by the structures formed in culture.

• Plantlets • Seedlings • Callus• Somatic Embryogenesis

• Plantlet formation• 1. Axillary shoot formation Meristem culture

Shoot culture • 2. Adventitious shoot formation Diploid plant

regeneration Haploid and triploid regeneration

• Axillary shoots form directly from existing meristems. The initial explant is a shoot tip or stem pieces.

• Adventitious shoots form indirectly after the initiation of new meristems. The initial explant is an internodal stem piece, leaf, root or other tissue without a pre-existing meristem

• Indirect adventitious shoots may also form after an intermediate callus step.

• Plantlet formation - Meristem cultures• Uses a shoot tip that is less than 1 mm in size.

Can be used for micropropagation. Mostly used for virus elimination

Plantlet formation - Shoot cultures

• This is the most common form of micropropagation. Uses a portion of the stem with one to several nodes.

• Plantlet formation - Shoot cultures• Axillary branching 2. Nodal cultures 3. Stool

shoots 4. Pseudocorms 5. Minitubers 6. Micrografting

• Plantlet formation - Shoot cultures• Axillary branching • The initial explant contains several nodes on a

single stem.• Lateral shoots are stimulated to form a dense

clump of shoots.

• Plantlet formation - Shoot cultures• Nodal cultures • Used with species with strong apical

dominance. Long shoots are cut into single nodes and placed vertically in the medium. The new shoot elongates and the process is repeated.

• Stool shoots • A shoot with several nodes is layered

horizontally on the medium. A thicket of stems emerge. Clumps are separated and subcultured.

• Pseudocorms • Pseudocorms are the structures initiated after

seed germination in orchids.

• Minitubers• Minitubers can be produced in plants that

naturally form tubers like potato and yam. Each minituber can be used as a propagule.

• Micrografting - an alternative to meristem culture

• Production of disease-free plants. Virus indexing. Micropropagation. Rejuvenation by serial micrografting. Send germplasm between countries.

• Plantlet formation• 1. Axillary shoot formation Meristem culture

Shoot culture 2. Adventitious shoot formation Diploid plant regeneration Haploid and triploid regeneration

antlet formation - Adventitious shoots

• Diploid plant regeneration Explants include: Leaf pieces

• Plantlet formation - Adventitious shoots• Diploid plant regeneration Explants include:

Leaf pieces, petioles

• Plantlet formation - Adventitious shoots• Diploid plant regeneration Explants include:

Leaf pieces, petioles, bulb scales, stem internodes, roots and callus.

• Haploid plant regeneration • Anther culture is a procedure for obtaining

haploid (half the chromosome number) plants from normally diploid plants. The discovery that pollen grains could develop into embryos was made by accident with Datura by Guha and Masheshwari in 1964.

• Techniques used to regenerate plants • 1. Plantlet formation 2. Seedling formation 3.

Callus formation 4. Somatic embryo formation

• Seedling formation Seed culture Embryo culture Embryo rescue Ovule and ovary culture

• Seed culture• In nature, orchid seeds rely on symbiotic

mycorrhizal fungi associations to germinate. However, they can germinate and develop into seedlings on the proper tissue culture medium without the fungal association

• Seedling formation - Embryo rescue • Immature embryos are removed from the

ovule before they abort. Primarily used in breeding to rescue embryos from interspecific crosses. These crosses are initially successful and the embryo forms. However, they never reach maturity.

• Seedling formation - Ovule and ovary culture • Also used in plant breeding for difficult

crosses. Unfertilized ovules are excised, placed in tissue culture and artificially pollinated. Fertilized ovules develop in culture to form seeds.