Intergeneric symmetric and asymmetric somatic hybridization in Festuca and Lolium

Summary Intergeneric symmetric and asymmetric somatic hybrids have been obtained by fusion of metabolically inactivated protoplasts from embryogenic suspension cultures of tall fescue (Festuca arundinacea Schreb.) and unirradiated or 10–500 Gy-irradiated protoplasts from non-morphogenic cell suspensions of Italian ryegrass (Lolium multiflorum Lam.). Genotypically and phenotypically different somatic hybrid Festulolium mature flowering plants were regenerated.Species-specific sequences from F. arundinacea and L. multiflorum being dispersed and evenly-represented in the corresponding genomes were isolated and used for the molecular characterization of the nuclear make-up of the intergeneric, somatic Festulolium plants recovered. The irradiation of Italian ryegrass protoplasts with 250 Gy X-rays prior to fusogenic treatment favoured the unidirectional elimination of most or part of the donor chromosomes. Irradiation of L. multiflorum protoplasts with 500 Gy produced highly asymmetric (over 80% donor genome elimination) nuclear hybrids and clones showing a complete loss of donor chromosomes.The RFLP analysis of the organellar composition in symmetric and asymmetric tall fescue (+) Italian ryegrass regenerants confirmed their somatic hybrid character and revealed a bias towards recipient-type organelles when extensive donor nuclear genome elimination had occurred.Approaches aimed at improving persistence of ryegrasses based on asymmetric somatic hybridization with largely sexually-incompatible grass species (F. rubra and Alopecurus pratensis), and at transferring the cytoplasmic male sterility trait by intra- and inter-specific hybridization in L. multiflorum and L. perenne, have been undertaken.Abbreviations cpDNA chloroplast DNA - CMS cytoplasmic male sterility - 2,4-D 2,4-dichlorophenoxy-acetic acid - IOA iodoacetamide - mtDNA mitochondrial DNA - RFLP restriction fragment length polymorphism