Molecular analysis of the fourth progeny of plants derived from a cytoplasmic male sterile chicory cybrid

Cytoplasmic male sterile (CMS) chicory cybrids have previously been obtained by fusion between chicory and CMS sunflower protoplasts. Preliminary restriction fragment length polymorphism analysis has shown mitochondrial recombination events in CMS plants and their progeny. The aim of this study was to investigate the fate of the mitochondrial genome of the fourth progeny derived from one CMS cybrid. Southern hybridization using several specific mitochondrial sequences as probes have revealed polymorphic patterns between the plants analysed and, consequently, the genetic instability of this genome. Presence of the sequence responsible for cytoplasmic male sterility in sunflower (orf522) was detected by polymerase chain reaction and confirmed by molecular hybridization in the CMS chicory plants; however, its part in CMS expression in chicory did not appear obvious. Moreover, different flowering phenotypes, including completely fertile plants occurred and no correlation could be established between the different mitochondrial profiles and the flowering types. These results suggested some hypotheses and questions about the molecular determinant of CMS in chicory, its regulation and expression and questions about the mitochondrial-nuclear interactions.