Molecular cytogenetic characterization and phylogenetic analysis of four species (Poaceae).

Chromosomes of four (Andersson, 1855) species including (Andersson, 1855), (Schumann & Lauterb, 1901), (Hackel, 1882) and (Chen & Renvoize, 2005) were analyzed using sequentially combined PI and DAPI (CPD) staining and fluorescence hybridization (FISH) with 45S rDNA probe. To elucidate the phylogenetic relationship among the four species, the homology of repetitive sequences among the four species was analyzed by comparative genomic hybridization (cGISH). Subsequently four species were clustered based on the internal transcribed spacer (ITS) of 45S rDNA. Molecular cytogenetic karyotypes of the four species were established for the first time using chromosome measurements, fluorochrome bands and 45S rDNA FISH signals, which will provide a cytogenetic tool for the identification of these four species. All the four have the karyotype formula of species, which is 2n = 2x = 38 = 34m(2SAT) + 4sm, and one pair of 45S rDNA sites. The latter were shown as strong red bands by CPD staining. A non-rDNA CPD band emerged in and some blue DAPI bands appeared in and . The hybridization signals of genomic DNA to the chromosomes of and genomic DNA to the chromosomes of were stronger and more evenly distributed than other combinations. Molecular phylogenetic trees showed that and were closest relatives, and and were also closely related. These findings were consistent with the phylogenetic relationships inferred from the cGISH patterns.