Phylogenetic relationships in the genus Avena based on the nuclear Pgk1 gene

The phylogenetic relationships among 76 Avena taxa, representing 14 diploids, eight tetraploids, and four hexaploids were investigated by using the nuclear plastid 3-phosphoglycerate kinase gene (Pgk1). A significant deletion (131 bp) was detected in all the C genome homoeologues which reconfirmed a major structural divergence between the A and C genomes. Phylogenetic analysis indicated the C(p) genome is more closely related to the polyploid species than is the C(v) genome. Two haplotypes of Pgk1 gene were obtained from most of the AB genome tetraploids. Both types of the barbata group showed a close relationship with the A(s) genome diploid species, supporting the hypothesis that both the A and B genomes are derived from an A(s) genome. Two haplotypes were also detected in A. agadiriana, which showed close relationships with the A(s) genome diploid and the A(c) genome diploid, respectively, emphasizing the important role of the A(c) genome in the evolution of A. agadiriana. Three homoeologues of the Pgk1 gene were detected in five hexaploid accessions. The homoeologues that might represent the D genome were tightly clustered with the tetraploids A. maroccana and A. murphyi, but did not show a close relationship with any extant diploid species.