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 r ubra (2n = 6x = 42 +/- 2B) and Vulpia fasciculata (2n = 4x = 28). Biot inylated 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 parent al chromosomes, GISH unequivocally identified chromatin from all regio ns along every Vulpia chromosome. Clearly, GISH has the potential for testing the theory that Vulpia genetic material has been transferred i nto Festuca rubra populations by introgressive hybridization. Genomic probing also discriminated between homogenetic (Vulpia-Vulpia and Fest uca-Festuca) and heterogenetic (Vulpia-Festuca) bivalents, showing tha t GISH can aid the interpretation of chromosome behaviour in meiotic n uclei of hybrids.