Genome Constitution Of Roegneria Alashanica Revealed By Genomic In Situ Hybridization And Nuclear RDNA ITS Sequence Analysis

Many species in Triticeae (Poaceae) own genes which can be able to resist to cold, drought, diseases and pests. Therefore, these species can be used for forage cultivating, and also be good for wheat breeding. There are more than20basic genome, including Ns, H, P, St, Y, W and E genome, etc. in the perennial Triticeae. But the genome compositions in many species of Triticeae are still unknown, which caused a lot of trouble for people to idengtify and use them effectively. Therefore, identification of the genome composition of the species in Triticeae is an important basis to utilize the genetic resources effectively.Roegneria C. Koch is a large genus in Triticeae, containing about130species in the word. Many species of Roegneria are important forage resources. According to awn, the species in Roegneria were divided into awned and awnless species. The awnless species in Roegneria involving R. alashanica, R. elytrigioides, R. magnicaespes and R. grandis. All of these four species are merely growing in China. According to chromosome analysis of Lu and Zhang et al., the genome contitutions of R. elytrigioides is St1St2, while R. grandis contains the StY genome. Cytological studies showed that R. alashanica and R. magnicaespes contain one set of St genome, while the other genome are still unknown.In order to explore the genome constitutions of Roegneria alashanica Keng, genomic in situ hybridization (GISH) and DNA sequence analysis of nuclear rDNA internal transcribed spacer (ITS) of R. alashanica and its relatives were carried out in the present study. The main purposes are:(1) to investigate the genome constitution of R. alashanica;(2) to study the relationships between Roegneria species with awnless and the Pseudoroegneria species. The main results are as follows:(1) Genome DNA of Roegneria elytrigioides (2n=4x=28, St1St2), Pseudoroegneria geniculata (2n=4x=28, StSt), Roegneria ciliaris (2n=4x=28, StY), Roegneria grandis (2n=4x=28, StY) were used as probe respectively, and blocking with genome DNA of Pseudoroegneria strigosa ssp. aegilopoides (2n=2x=14, St), in the genomic in situ hybridization (GISH) with R. alashanica. The results show that:1) when R. elytrigioides and Pse. geniculata was used as probe,14chromosomes showed yellow fluorescence signals;2) when R. ciliaris was used as probe, none of the chromosomes showed fluorescence signals;3) when R. grandis was used as probe, some chromosomes show little spotty green hybridization singals. The results indecate that R. alashanica contains one set of St genome, while the other set of genome has non-homology with the Y genome.(2) Genome DNA of Pseudoroegneria libanotica was used as probe, while genome DNA of Hordeum bogdanii (2n=2x=14, H), Agropyron cristatum (2n=2x=14, P), Lophopyrum elongatum (2n=2x=14, Ee), were used as blocking, respectively. The results show that:1) the28chromosomes all show strong green fluorescence signals when blocking with genome DNA of H. bogdanii;2)14-16chromosomes show green fluorescence signals when blocking with Lo. elongatum;3)21chromosomes all show green fluorescence signals when blocking with Ag. cristatum. The results indicate that R. alashanica contained one set of St genome and the other set was closely related to St, E and P genome, while it has non-homology with the H genome.(3) Genome-DNA of Lophopyrum elongatum, Agropyron cristatum, Hordeum bogdanii were used as probe, respectively, while DNA of Pseudoroegneria libanotica were used for blocking. The results show that:1) the12-14chromosomes showed green fluorescence signals when probed with DNA of Lo. elongatum (Ee);2)7-10chromosomes showed weak green fluorescence signals when probed with DNA of Ag. cristatum (P);3) all chromosomes showed none green hybridization fluorescence when probed with DNA of H. bogdanii (H). The results indicat that R. alashanica contains one set of genome which is closely related to E and P genome, while it has non-homology with the H genome.(4) The ITS sequences of11Roegneria accessions (StY or StSt),9Pseudoroegneria accessions (St or StSt),2Hordeum accessions (H),2Lophopyrum (Ee or Eb), one Agropyron accessions (P),4Elymus accessions (StH),2Elytrigia accessions (EeSt or EbEeSt),2Douglasdeweya accessions (StP),2Hordeum accessions (H),2Australopyrum accessions (W), and2Psathyrostachys accessions (Ns) totally37accessions were used to estimate the phylogenetic relationships. In the neghbour-join tree, all the accession were clastered to four clades, named St, W/P, H and Ns,W/P, respectively. The St clade is the most enormous, and incudes Pseudoroegneria, Roegneria and most of Elymus species. All the sequences of R. alashanica were clustered into two clades, one was clastered in St clade, while the other one was claded with Agropyron (P) and Australopyrum (W). The result indicates that one set of genome in R. alashanica is St genome, and the other set genome of R. alashanica is related to St and P.It is concluded that R. alashanica contains one set of the St genome, while the other set of genome is related to St, P and E genome, but it has non-homology to the H or Y genome.