Novel ‘homeotic’ CMS patterns generated inNicotianavia cybridization withHyoscyamusandScopolia

Abstract

Cytoplasmic hybrids (cybrids) that contain nuclear genetic material from Nicotiana tabacum and cytoplasms from Hyoscyamus niger or Scopolia carniolica were constructed by protoplast fusions. Both types of hybrids exhibited cytoplasmic male sterility (CMS). Furthermore, unusual floral morphogenesis marked by 'green flowers' deprived of corolla and stamens occurred in the majority of the lines. Backcrosses of these plants with wild-type tobacco demonstrated a maternal inheritance of the 'green flower' trait. After repeated transfer of cytoplasm ('donor-recipient fusion') from cytoplasmic hybrid N. tabacum (+H. niger) to albino plastome mutant N. tabacum DSR A15, male sterile tobacco plants with two types of flowers were recovered ('green flowers' and corolla-containing flowers with transformed stamens). RFLP analysis confirmed that N. tabacum (+ H. niger) and N. tabacum (+S. carniolica) as well as their sexual progenies contained plastids from H. niger and S. carniolica, respectively. Mitochondrial DNA within the hybrids N. tabacum (+H. niger) originated from H. niger, but was obviously altered. Repeated parasexual transmission, cybrids in the combination of N. tabacum+N. tabacum (+H. niger), reflected similar characteristics. Cybrids, N. tabacum (+S. carniolica) and their sexual progeny, which resulted after pollination with wild-type tobacco, contained a modified mtDNA generally originating from tobacco. Further histological analysis established the dramatic difference in the composition of 'green flowers' and flowers of wild-type tobacco. Therefore, the construction of tobacco cybrids with foreign cytoplasms provides a functional method for the de novo generation of alternative CMS types.