4 Discussion
The morphological characters of R. yenchiana differ from all
species previously described in Roegneria , especially in its
rudimentary spikelets at the inflorescence base, rectangular glumes, and
two short mucros in lemmas. GISH conformed that R. yenchicata is
a tetraploid (2n=4x=28) with the StY genome constitution.
Phylogenetic analysis based on all the three unlinked single-copy
sequences showed that the St -genome homoeologous types ofR. yenchiana were grouped with the sequences ofPseudoroegneria and Roegneria , and the Y -genome
homoeologous types of R. yenchiana were clustered with the
sequences of Roegneria with high statistic supports (BS
> 70% and PP > 0.9). In the phylogenetic tree
inferred from the combined chloroplast sequences, all the three
accessions of R. yenchiana were grouped withPseudoroegneria and Roegneria (BS = 81% and PP =
1.0). These results indicated that Pseudoroegneria andRoegneria are closely related to R. yenchiana . Combined
with GISH analysis, it can be concluded that the St genome ofR. yenchiana is derived from the genus Pseudoroegneria ,
and the Pseudoroegneria served as the maternal donors during its
polyploid speciation.