Fan-shaped Spectrums of Species and Paleopolyploidy for Foundation of Crossbreeding Evolution

Comment: 5. Somatic Cell HybridizationSomatic cell hybridization is a technique of fusion between different somatic cells from different tissues or species to produce hybrid cells in a cell culture. There is often one fused nucleus and the nuclear fusion can allow the recombination of chromosomal DNA for creating novel nuclear and/or cytoplasmic genomes, and produce a progeny with mixed characteristics. There are no hurdle of incompatibility (at interspecific, inter-generic or even at inter-kingdom levels) for the protoplast fusion (Sidebottom and Ringertz, 1984).Its major contribution to plant breeding is in overcoming common crossing barriers among plant species and in organelle genetics. The resulting hybrid has the chromosomes of both plants and it thus similar to polyploid plants. Protoplast fusion is a wonderful approach to overcome sexual incompatibility between different species of plants. Example-production of plant like pomato from potato and tomato (Sink et al 1992).In the animals, fusion of two different cells and production of a hybrid cell have been successfully achieved. It is interesting to note that the cells of taxonomically different animals can fuse and form hybrids. For instance, human-rodent somatic cell hybrids are developed by mixing human and mouse cells in the presence of the sendai virus. The hybrids contain the entire complement of the mouse genome and a few human chromosomes, because most human chromosomes are lost from the hybrid cell lines (Ohno-Shosaku et al 1984).The process of fusion can be achieved by spontaneous, mechanical, or induced fusion methods. As the spontaneous fusion, it is a natural process as is observed in case of egg fertilization. Actually, somatic hybridization is suitable for haploid protoplasts because fusion between two diploids results in the formation of an amphidiploid, which is not favorable.The cell-cell fusion remains poorly understood. However, it provides important experimental evidences that the cells, nuclei and DNAs from species of far relatives can fuse together and produce a hybrid cell with a new set of chromosomes. This means the two germ cells (sperms and ovules) from far relatives have more opportunity to combine and develop.