Mitochondrial recombination in cytoplasmic hybrids of Nicotiana tabacum by protoplast fusion

Abstract

We have previously regenerated tobacco plants from fused protoplasts isolated from two varieties of Nicotiana tabacum. The parent cells had distinct morphological nuclear and cytoplasmic markers, enabling us to recognise, among the whole regenerated plants, those with a single parental nucleus and a hybrid cytoplasm produced by the mixing of the two parental cytoplasms¹. Genetic analysis of their progeny has confirmed that the phenotypes of these cytoplasmic hybrids (or cybrids) are stable and maternally inherited. Analysis with restriction endonuclease has shown that only one or the other parental chloroplast DNA is present in the progeny of the cybrids². We report here, however, that the mitochondrial (mt) DNAs of cybrids are different from those of the parents and from the mixture of the two. The new DNAs result from mitochondrial recombination.