AN EVALUATION OF RDNA VARIATION IN LOLIUM SPECIES (RYEGRASS)

Species of the genus Lolium are important fodder and turf grasses for agricultural and amenity use world-wide. Difficulties currently exist regarding the taxonomy of Lolium species and also in the demarcation b etween Lolium and the genus Festuca with the debate focusing on the st atus of Festuca pratensis and its relations. The diversity in ribosoma l DNA (rDNA) in Lolium was investigated. Cloned probes for rDNA, deriv ed from the intergenic spacer (IGS-M) and transcribed regions (COD-M) of mustard (Sinapis alba) were used to investigate species relationshi ps. Genomic DNA from seven Lolium taxa, F. pratensis, and xFestulolium braunii, were assessed for variation in rDNA by RFLP. Data support co ntinued recognition of existing Lolium species' demarcations, and prov ided more taxonomic insight between allogamous Lolium taxa and F. plat ensis. The COD-M and IGS-M probes grouped taxa by reproductive mode. T he IGS-M probe distinguished all species as unique entities and establ ished that hybrids, xFestulolium braunii and Lolium xboucheanum, had r DNA phenotypes that were composites of their parental species. The evo lution of the ribosomal repeat unit is discussed and the potential for further rDNA taxonomic study in Lolium is considered.