Characterization Of Karyotype And Chromosome Homoeology Groups Of Pseudoroegneria Libanotica Based On Common Wheat Single-copy CDNA-FISH

Pseudoroegneria is an extremely important genome donor genus of the Triticeae,with more than 60% of perennial Triticeae species containing the St genome.Therefore,Pseudoroegneria is important in the phylogeny of the Triticeae.Plants in this genus have excellent disease resistance and stress tolerance properties,which can provide an abundant gene pool for wheat crops and forage breeding.To date,the homoeologous chromosomes of the St genome have not been fully distinguished,the standard karyotype has not been established,and homoeology groups among Triticeae genomes have not been determined.In this study,we generated 32 single-copy gene c DNA-FISH probes from common wheat,identified 1St～7St homology chromosome groups in diploid Pseudoroegneria libanotica,established the standard molecular cytogenetic karyotype of the St genome,and obtained the genome homoeology of the Triticeae specie.The main results are as follows:1.We distinguished the 1St～7St homologous chromosomes of Pse.libanotica and established the standard karyotypes using 32 wheat c DNA probes.The c DNA probe 5L-2displayed signals on the long arm of 5St and the short arm of 2St,indicating that a gene or fragment on the long arm of 5St was duplicated and inserted into the short arm of 2St.The chromosome sizes of the St genome range from 4.35 to 5.59 μm,the 1St with a large secondary construction region and 5St with a small secondary construction region on their short arm.The 2St is the longest and 4St is the shortest with a relative chromosome length of 16.13% and 12.20%,respectively.The arm ratio value varied from 1.10 to 2.96,they belong to 7St and 1St respectively,with an average arm ratio of 1.65.The centromere index ranged from 37.33 to 47.64.The karyotype type of Pse.libanotica is 2A and the karyotype formula is 2n=2x=14=10m+4sm(sat).2.The relative positions of 32 c DNA probe sequences on the St chromosome were measured.Compared with the location of other Triticeae species,we established a collinearity map and analyze the homoeology of the St genome with other genomes.The St genome of Pse.libanotica has the strongest covariance with sub-genomes B and D of wheat and genome M of Ae.comosa,followed by sub-genome A of wheat,and P genome of Ag.cristatum,whereas,the C genome of Ae.markgrafii and U genome of Ae.umbellulata displayed more variations,which may imply a distant genetic relationship.The standard molecular cellular karyotype of Pse.libanotica established in this study will significantly improve the understanding of the St genome at the chromosome and genome levels and lay the foundation for St genome utilization.