Schematic representation of shared nucleotide polymorphisms along the PPR-1 and PPR-2 coding sequences. The multiple gene alignment (additional file 1) was used to detect shared polymorphisms between PPR-1 or PPR-2 and the genes from the D81Rfo sequence. Flags represent positions of polymorphisms shared by the considered gene and PPR-A (circles), PPR-B (squares), or PPR-C (triangles). Open forms indicate a single position. Filled forms indicate several positions that were too close on the sequence to be distinctly represented on the diagram. The numbers above filled forms indicate the number of positions concerned. The end section of PPR-1, which contains the intron sequence, is treated as a block sharing 22 polymorphisms with PPR-B and 1 with PPR-C (regions with gaps were not considered).