Asymmetric Hybrids - Many somatic hybrids exhibit the full somatic complement of one parental species, while all or nearly all chromosomes of the other parental species are lost during the preceding mitotic divisions; such hybrids are referred to as asymmetric hybrids.

The available evidence suggests that such hybrids are likely to show introgression of chromosome segments from the eliminated genome(s).

Asymmetric hybrids can be obtained even from those combinations, which normally produce symmetric hybrids by the following approach: protoplasts of one of the parental species are irradiated with a suitable dose of X-rays or gamma-rays to induce extensive chromosome breakage. In such cases, chromosome segment introgression may be markedly enhanced.