Submitted to: Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 31, 2008
Publication Date: April 3, 2009
Citation: Okito, P., Wu, Y., Wang, R., Mott, I.W. 2009. Y-Genome Specific STS Marker in Pseudoroegneria and Elymus Species (Triticeae: Gramineae). Genome 52:391-400. Interpretive Summary: The genus Elymus L. (Triticeae, Poaceae) is composed of approximately 150 perennial species; it is the largest, most widely distributed, and most morphologically diverse taxon in the Triticeae. It is a complex group of allopolyploids containing multiple copies of different genomes, having a genomic formula of StH, StP, StY, StStY, StHY, StPY, or StWY. All the Elymuus species share a common St genome originated from the genus Pseudoroegneria, while the H genome originated from Hordeum, P from Agropyron and W from Australopyrum, but the donor of Y genome in Elymus is still unknown. It has been hypothesized that the St and Y genomes originated from a common ancestor genome. We first tested a putative Y genome specific STS marker on Elymus species for its reliability in detecting the Y genome, and then, used it to screen accessions of Pseudoroegneria and Hordeum species for identifying possible Y genome donors. We found rare accessions of 3 Pseudoroegneria species as potential Y genome donors, especially with P. spicata as a strong candidate of Y genome donor in E. longearistatus. Thus, our findings support the fore-mentioned hypothesis.
Technical Abstract: The tribe Triticeae Dumortier in the grass family (Poaceae) includes the most important cereal crops (e.g., wheat, barley, and rye) and some economically important forage grasses. Elymus L. is the largest and most complex genus in the Triticeae tribe with approximately 150 species occurring worldwide. The genomic constitutions of ~40% Elymus species are unknown, and some have unverified genomic combinations. Of those known for genome constitutions, Elymus species have a genomic formula of StH, StP, StY, StStY, StHY, StPY, or StWY. However, the origin of the Y genome is unknown because no diploid species had been identified as the Y genome donor. A putative Y genome specific random amplified polymorphic DNA (RAPD) marker was converted to a Sequence Tagged Site (STS) marker. The reliability of this STS marker for confirming the presence of Y genome was demonstrated using 42 accessions of Elymus. Excluding those Triticeae genomes having long chromosomes, the STS-PCR for the Y genome marker was then assayed only on 43 accessions of diploid Pseudoroegneria species having the St genome and 113 accessions of Hordeum that have the Xa or Xu genome in order to identify possible donors of the Y genome. A rare accession of P. spicata (Pursh) A. Love was found to possess sequences that most closely related to those from the tetraploid E. longearistatus (Boiss.) Tzvelev (StStYY), making P. spicata the most likely donor of Y genome. Our findings support the hypothesis that the Y genome in some Elymus species shares a progenitor genome (designated StY) with the St genome of Pseudoroegneria.