ABSTRACT
The objectives of somatic hybridization may be to develop the following: (1) somatic or parasexual hybrids comprised of the complete genome of two “parents,” (2) asymmetric somatic hybrids where there has been only partial genome transfer between species, or (3) cytoplasmic hybrids (cybrids) with the nucleus of one parent and the cytoplasm of another. Somatic hybrids between closely related species are generally polyploid and have the potential of fertility. Potato has been the object of somatic hybridization with a range of related species from sexually compatible tuber-bearing Solanum relatives to sexually incompatible nontuberous Solanum, including tomato (Solanum lycopersicum L.), nightshade (Solanum nigrum L.), and tobacco. Both its plasticity in tissue culture and facile vegetative propagation have made the potato attractive to geneticists wishing to examine the potential of somatic hybridization in an important economic crop. Somatic hybrids between potato (Solanum tuberosum L.) and a weedy, nontuber-bearing relative, S. brevidens Phil., contained the additive number of chromosomes of the two parents (i.e., 72 with 48 from potato and 24 from S. brevidens). These somatic hybrids could be backcrossed to potato, resulting in fertile tuber-producing plants with considerable breeding potential as sources of disease resistance (Helgeson et al., 1986).
