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Symmetric Hybrids - Many symmetric hybrids have been produced between sexually incompatible species. Some of these possess and express useful genes and are fertile; these have been ordered into breeding programmes. Symmetric hybrids provide the following opportunities.

1. Somatic hybrids can be produced between a nonflowering and a male sterile strain of a crop species.

2. The genetic base of some allopolyploid crops may be narrow e.g., in case of B. napus. Genetic base of a crop species is to total amount of genetic variation present in the crop. The genetic base in such cases can be widened considerably by synthesizing the species in question.

3. The symmetric hybrids can be used in a hybridization programme to transfer desirable characters from a related species into a crop species. A commercially useful gene transfer has been made from N. rustica to N. tabacum.

The somatic hybrids from these two species were backcrossed three times to N. tabacum. Resistance to black rot and high alkaloid content were transferred from N. rustica fusion parent. Selection in the backcross generations yielded two varieties, viz., Delgold and A.C. Chang. Delgold became a popular variety in Ontario, Canada.

4. Some somatic hybrids may possess such desirable features that may make them commercially useful. Some of the somatic hybrids between dihaploid clones of S. tuberosum (2n = 2x = 24) and the wild relative S. phureja (2n = 2x = 24) gave markedly higher tuber yields than the two fusion parents.

One hybrid clone yielded 3-times as much tuber as the potato commercial variety Bintje. Somatic hybridization is being used for potato improvement in the Netherlands.

5. Somatic hybridization can generate some novel materials that may be very useful in genetic, physiological, biochemical and other studies.

 
 

 
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