Taxonomic relationships and interspecific hybridization in the genus Lolium (grasses)

Phylogenetic trees of the 8 species of the genus Lolium and of Festuca pratensis have been derived from frequency data at 13 isozyme loci using different distance algorithms. The best tree was obtained by the distance-Wagner method with the Cavalli-Sforza and Edwards chord distance. This tree appears robust when tested by bootstrap resampling of loci. This confirmed previous knowledge on species relationships in the genus Lolium, with supplementary data on the taxonomic position of the less studied L. persicum and L. canariense. Attempts were made to hybridize 4 Lolium species and F. pratensis. True interspecific hybrids, as confirmed by isozyme markers, were obtained for L. perenne x L, temulentum, L. temulentum x L. rigidum, L. temulentum x L. canariense and L. canariense x F. pratensis. This is the first report of this new form of Festulolium, which was obtained at a fairly high frequency, giving argument to a possible genetic proximity between L. canariense, an endemic species restricted to Atlantic islands, and F. pratensis, which has a more widespread, northern distribution. However, chromosome pairing analysis at meiosis did not support this conclusion, as the Fl L. canariense x F: pratensis definitely showed a higher level of asynapsis compared to that reported for L. perenne x F:pratensis. The apparently close relation between L. canariense and F: pratensis seen on the tree is therefore postulated to be an artefact, due to the low number of loci studied.