GENOMIC IN-SITU HYBRIDIZATION IDENTIFIES PARENTAL CHROMOSOMES IN THE WILD GRASS HYBRID X FESTULPIA-HUBBARDII

Genomic in situ hybridization (GISH) was used to discriminate between the parental chromosomes of the grass x Festulpia hubbardii (2n = 5x = 35 +/- 2B), a naturally occurring pentaploid hybrid between Festuca rubra (2n = 6x = 42 +/- 2B) and Vulpia fasciculata (2n = 4x = 28). Biotinylated total genomic DNA of V. fasciculata, mixed with an excess of unlabelled F. rubra genomic DNA as a block, hybridized preferentially in situ to mitotic Vulpia chromosomes. Unlike Giemsa C-banding, which provided a physical marker only for the terminal regions of the parental chromosomes, GISH unequivocally identified chromatin from all regions along every Vulpia chromosome. Clearly, GISH has the potential for testing the theory that Vulpia genetic material has been transferred into Festuca rubra populations by introgressive hybridization. Genomic probing also discriminated between homogenetic (Vulpia-Vulpia and Festuca-Festuca) and heterogenetic (Vulpia-Festuca) bivalents, showing that GISH can aid the interpretation of chromosome behaviour in meiotic nuclei of hybrids.