Sorting out of cytoplasmic elements in somatic hybrids of Petunia and the prevalence of the heteroplasmon through several meiotic cycles

Abstract

In previous papers we demonstrated direct transfer of cytoplasmic male sterility (cms) in Petunia via protoplast fusion. We showed further that a heteroplasmic state with respect to male sterility and fertility was obtained. Once this heteroplasmic state was achieved, the hypothetical sterility elements (te) and the fertility elements (fte) sorted out. In the present paper we describe a large population of somatic hybrid plants with tetraploid hybrid nucleic and plasmonic variation. Most of the somatic hybrid plants (3923) were homoplasmic male fertile (mf). 92 plants were homoplasmic male sterile (ms) and 32 were heteroplasmic plants containing both ste and fte. Somatic and gametic sorting out occurred only in sterile tissue, with one exception; gametic sorting out occurred in a single F3 fertile segregant. Nevertheless, in some cases, the two kinds of elements coexisted in a single heteroplasmic cell, prevailing through several meiotic cycles. The data presented in this paper indicate that the genetic nature of the ste in petunia is unique in comparison with other cytoplasmic sterilities studied.