Somatic Hybridization of Plants

Somatic Hybridization:

Fusion between protoplasts of the selected parents is induced by a solution of polyethylene glycol (PEG), or by very brief high voltage electric current. Somatic hybridisation allows the production of hybrids between lines and species that cannot be produced normally by means of sexual hybridisation.

Fusion of cytoplasm of two protoplasts results in coalescence of cytoplasm. The nuclei of two protoplasts may or may not fuse together even after fusion of cytoplasms. The binueleate cells are known as heterokaryon.

When nuclei are fused the cells are known as hybrid, and when only cytoplasms fuse and genetic information from one of the two nuclei is lost is known as cybride i.e, cytoplasmic fuse and genetic information from one of the two nuclei is lost is know as cybrid i.e, cytoplasmic hybrid.

However, production of cybrids which contain the mixture of cytoplasms but only one nuclear genome can help in transfer of cytoplasmic genetic information from one plant to another. Thus, information of cybrid can be applicable in plant breeding experiments.

For example, in China, cybrid technology in rice is a great success. Such plants are very useful in producing hybrid seeds without emasculation. Today, cybrid technology has successfully been applied to carrot, mustard, citnis, tobacco and sugar beet.

Somatic hybrids may also be used for gene transfer, transfer of cytoplasm and production of useful allopolypoloids.

Tissue and protoplast cultures have been used in genetic engineering for the transfer of DNA and extrachromosomal bodies — plasmids, mitochondria, chloroplasts, nif (nitrogen fixing) genes from the nitrogen fixing bacterium Klebsiella pneumoniae to a strain of the colon bacterium Escherichia coli. Isolated protoplasts have great advantage in all the afore mentioned uses.

For transformation purposes cultured apical meristems are also usable because these can easily be regenerated into whole plants and also because intact DNA taken up by plants appears to be rapidly transported to meristematic regions, where growth and differentiation are centred.