Molecular evolution and nucleotide diversity of nuclear plastid phosphoglycerate kinase (PGK) gene in Triticeae (Poaceae)

Levels of nucleotide divergence provide key evidence in the evolution of polyploids. The nucleotide diversity of 226 sequences of pgk1 gene in Triticeae species was characterized. Phylogenetic analyses based on the pgk1 gene were carried out to determine the diploid origin of polyploids within the tribe in relation to their A(u), B, D, St, Ns, P, and H haplomes. Sequences from the Ns genome represented the highest nucleotide diversity values for both polyploid and diploid species with pi = 0.03343 and theta = 0.03536 for polyploid Ns genome sequences and pi = 0.03886 and theta = 0.03886 for diploid Psathyrostachys sequences, while Triticum urartu represented the lowest diversity among diploid species at pi = 0.0011 and theta = 0.0011. Nucleotide variation of diploid Aegilops speltoides (pi = 02441, presumed the B genome donor of Triticum species) is five times higher than that (pi = 0.00483) of B genome in polyploid species. Significant negative Tajima's D values for the St. A(u), and D genomes along with high rates of polymorphisms and low sequence diversity were observed. Origins of the A(u), B, and D genomes were linked to T. urartu, A. speltoides, and A tauschii, respectively. Putative St genome donor was Pseudoroegneria, while Ns and P donors were Psathyrostachys and Agropyron. H genome diploid donor is Hordeum. (C) 2013 Elsevier B.V. All rights reserved.