Genetic relationships of tetraploid Elymus species and their genomic donor species inferred from polymerase chain reaction-restriction length polymorphism analysis of chloroplast gene regions

The genetic relationships of 38 individuals from 13 Elymus tetraploid species, two Pseudoroegneria species and one Hordeum species were examined using polymerase chain reaction-restriction length polymorphism analysis of chloroplast gene regions. The 13 Elymus species contain SH and SY genomes with either a single spikelet or multiple spikelets per rachis node. The Pseudoroegneria and Hordeum species contain an S genome with single spikelet per rachis node and an H genome with multiple spikelets per rachis node, respectively. Four chloroplast gene regions, trnD-trnT intron, trnK [tRNA-Lys (UUU) exon1]-trnK [tRNA-Lys (UUU) exon2], trnC-trnD, and rbcL were amplified with specific primers and subsequently digested with up to 16 different restriction enzymes. Interspecific variation was detected in the four regions. A dendrogram based on similarity matrices using the unweighted pair group method with arithmetic average algorithm separated the 38 individuals into two distinct groups: the Elymus and Pseudoroegneria species as one group and Horduem as a second group. This result corresponded well with previous findings, and strongly suggested that a Pseudoroegneria species is the maternal donor to tetraploid Elymus species. Unlike previous studies using nuclear genes, the chloroplast DNA used in this study could not clearly separate the SY-genome species from SH-genome species. No clear separation between the species with a single spikelet per rachis node and the species with multiple spikelets per rachis node was found. Intra-specific variation was detected for the species studied. These observations provide molecular evidence for the highly diverse nature of the Elymus gene pool based on morphological characteristics.