Phylogenetic relationships among low-ploidy species of Poa using chloroplast sequences.

Abstract

Species of the genus Poa are taxonomically and genetically difficult to delineate owing to high and variable polyploidy, aneuploidy, and challenging breeding systems. Approximately 5% of the proposed species in Poa are considered to include or comprise diploids, but very few of those diploids are represented in seed collections. Recent phylogenetic studies of Poa have included some diploid species to elucidate Poa genome relationships. In this study, we build upon that foundation of diploid Poa relationships with additional confirmed diploid species and accessions, and with additional chloroplast sequences. We also include samples of P. pratensis and P. arachnifera to hone in on possible ancestral genomes in these two agronomic and highly polyploidy species. Relative to most species of Poa, Poa section Dioicopoa (P. ligularis, P. iridifolia, and P. arachnifera) contained relatively large chromosomes. Phylogenies were constructed using the TLF gene region and five additional chloroplast genes, and the placement of new species and accessions fit within chloroplast lineages previously reported better than by taxonomic subgenera and sections. Low-ploidy species in the P chloroplast lineage, such as P. iberica and P. remota, grouped closest to P. pratensis.