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What are the applications of somatic cell hybridisation?
It has been known since the 60's that somatic cells from the same or different species in culture could spontaneously fuse to form polyploid cells. The product of fusion was called Homokaryon if the two parental cells come from the same species, and Heterokaryon or Somatic Cell Hybrid if the fusion was site-specific.
The hybrid cells could divide by mitosis and proliferate and thus could be maintained in culture. Cell fusion is followed by nuclear fusion to produce uninucleate hybrid cells or Synkaryons.  The rate of cell fusion is very low; about one cell fuses in million of cells.

The applications are
1. Means of Genetic Recombination in Asexual or Sterile Plants:
Somatic cell fusion appears to be the only approach through which two different parental genomes can be recombined among plants that cannot reproduce sexually. Similarly,  protoplast of sexually sterile plants can be fused to produce fertile diploids and polyploids. There are several reports describing the amphidiploid and hexamploid plants produced from fusion of haploid protoplasts of tobacco.

2.  Overcoming Barriers of Sexual Incompatibility:
In plant breeding programmes, sexual crossing at Interspecific and Intergeneric levels often fails to produce hybrids due to incompatibility barriers, which can be overcome by somatic cell fusion.

3. Cytoplasm Transfer:

Power et.al. (1975) fused mesophyll protoplasts of Petunia with cultured cell protoplast of the crown gall of Parthenocissus and selected a line which contained the chromosomes of only Parthenocissus but exhibited some of the cytoplasmic properties of Petunia for some time. This was followed by direct application of cybridisation in agricultural biotechnology by transfer of cytoplasmic male sterility from Nicotiana techne to N. tabacum, N. tabacum to N.sylvestris and Petunia hybrida to P. axillaries. Besides cytoplasmic male sterility, the genophore of the cytoplasm codes for number of practially important traits, such as the rate of photosynthesis, low or high temperature tolerance, and resistance to disease or herbicides.


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