Morphological differentiation in four species of the genus Lolium

Three hundred and sixteen accessions belonging to four species of the genus Lolium were analysed for morphological differentiation following field tri als. Principal component analysis (PCA) was shown to explain over 74% of th e variation with the date of ear emergence, spike height and flag leaf leng th and width being responsible for the major differentiation. L. perenne se parated into two groups following PCA, cluster analysis and k-means cluster ing, as a result of floral initiation in the sowing year. Those accessions that did not attain floral initiation until the second year were found to b e from northern Europe. The inbreeder L. temulentum was separated from the three outbreeding species, L. perenne, L. multiflorum and L. rigidum, which are themselves distinct from each other although there is some introgressi on between them, especially between L. multiflorum and L. rigidum. The resu lts are discussed in relation to selection of a core collection of Lolium a ccessions.