rbcL Plastid Pseudogene as a Tool for Orobanche (Subsection Minores) Identification

Abstract: Among members of the Orobanchaceae, parasitism has led to a drastic reduction in the morphological characters useful in identification. This is especially the case of species belonging to the subsection Minores (section Orobanche ), which is a real tangle for agronomists and botanists. In this study, more than 120 specimens collected in the west of France were studied for their morphological characters and molecular markers. Their rbcL plastid gene was analyzed by RFLP and nucleotide sequencing. Because of several substitutions, insertions and deletions in the coding sequence, leading to stop codons and frameshift, this rbcL gene could be considered as a pseudogene. Variations in both 5' upstream and coding regions allowed us to distinguish among specimens inside the Minores subsection. It was then possible to point out morphological characters, not used in floras, that fit with molecular analysis and confirm the existence of four taxa. Consequently, a new key to species determination using molecular analysis or morphological characters or a combination of both is proposed for O. hederae, O. amethystea, O. minor and O. loricata. Finally, the value of plastid pseudogenes in taxonomy is discussed.