somatic hybridization and cybrid

Somatic hybridization :- 

Somatic hybridiztion refers to crossing of crop plants though fusion of somatic cell.

The fusion of somatic cell takes place through protoplasts.

Protoplast is a plant, bacterial or fungal cell that had its cell wall completely or partially removed using either mechanical or enzymatic means.

Feature of somatic hybrid :- 

This method essential for regeneration of somatic hybrid in whole plant.

In this method there is equal contribution of cytoplasam from both parents.

For regenration of protoplast specific nutrient medium is used which differs from species to species.

Types of somatic hybrid:- 

1.Inter specific hybrid

2.Intra generic hybrid

3.Intertribal hybrid

• Symmetrical hybrid

• Asymmetrical hybrid

• Cybrids

Cybrid:- 

Cybrids :- Those somatic hybrid that involve normal protoplast of one species and nucleus less protoplast of another species are known as cybrids . 

Such hybrids are useful in transfer of CMS from one species to other.

Cybrids are produced in variable frequencies in normal protoplast fusion experiments due to one of the following:- 

I. Fusion of normal protoplast of one species with an enucleated protoplast of the other species.

II.Elimination of the nucleus of one species from anormal heterokaryon.

3. Gradual elimination of the chromosomes of one species

from a hybrid cell during the subsequent divisions.

Cybrids may be produced in relatively high frequency by

i. Irradiating protoplast of one species prior to fusion in order to inactivate their nuclei,

ii.By preparing enucleate protoplast of one species and fusing that with normal protoplast of other species.

Limitation :- 

 Used for vacuolated cells like onion bulb scale,

radish and beet root tissues

 Low yield of protoplast

 Laborious and tedious process

 Low protoplast viability