Molecular analysis of the mitochondrial genome of Helianthus annuus in relation to cytoplasmic male sterility and phylogeny.

A circular supercoiled mitochondrial DNA plasmid P1 (1.45 kb) is shown in both normal fertile plants of Helianthus annuus, and some cytoplasmic male sterile lines (CMS A and CMS P). In contrast, no plasmid is found in some other types of CMS C, I, B and K. A circular supercoiled DNA (P2) of higher molecular weight (1.8 kb) is observed in CMS F. The mitochondrial plasmid P1 was cloned, nick-translated and hybridized with native mitochondrial DNA from different lines of male fertile, CMS or wild Helianthus. No sequence homology has been detected between plasmid DNA P1 and high molecular weight mitochondrial DNA in any line examined. A slight hybridization occurs between plasmids P1 and P2. Thus, there is no apparent relationship between mitochondrial plasmid DNA and CMS or Helianthus species. On the contrary, each Helianthus CMS and male fertile strain can be characterized by digestion fragment patterns (Sal I and Bgl I). Analysis of mitochondrial DNA from wild Helianthus strains indicated a relation between some CMS and the strain from which they were maternally derived, as for example CMS I and H. annuus ssp lenticularis and CMS F and H. petiolaris fallax. On the basis of restriction endonuclease patterns, a CMS phylogenic tree is proposed which illustrates a molecular polymorphism in the mitochondrial genome of Helianthus.