Sequence variation at the three chloroplast loci (matK, rbcL, trnH-psbA) in the Triticeae tribe (Poaceae): comments on the relationships and utility in DNA barcoding of selected species

Abstract

This study presents a phylogenetic analysis of the selected representatives of the Triticeae tribe and the assessment of possibilities of species identification on the basis of sequence variation in the three regions from the chloroplast DNA (matK, rbcL and trnH-psbA). The analysis included diploid and polyploid species of the following genomic compositions: E b , E e , H, I, Ns, St, Ta, Xu, NsXm, XoXr, XuXu, E b E e , E b E b E e , E b E e St, StH, StStH. The obtained matK and rbcL sequences revealed three well-supported clades: (1) Elymus, Lopophyrum, Pseudoroegneria, Thinopyrum (genomes E b , E e , St, StH, E b E e , E b E b E e , E b E e St, StStH); (2) Leymus, Hordelymus, Psathyrostachys (genomes Ns, NsXm, XoXr); (3) Hordeum (genomes H, I, Xu). This results support the view that the analyzed Elymus species (E. caninus, E. repens) acquired the Pseudoroegneria St genome maternally. They also indicate that Hordelymus europaeus carries the Ns genome from Psathyrostachys and point at the maternal origin of this component. Moreover, the presented results confirm the contribution of Psathyrostachys in the origin of Leymus as well as indicate the maternal character of this input. Differentiation observed within the Hordeum clade aligns with the alleged genome composition of the analyzed species. The DNA barcoding potential of the analyzed sequences was low. Nevertheless, several informative polymorphisms were found like e.g. the matK substitution specific for Thinopyrum bessarabicum, the trnH-psbA substitution differentiating Leymus arenarius from Psathyrostachys juncea and the group of species-specific deletions within trnH-psbA. In the DNA barcoding context we have also demonstrated negative importance of the high frequency cpDNA inversion leading to intraspecific variation.