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 trials. Principal component analysis (PCA) was shown to explain over 74% of the variation with the date of ear emergence, spike height and flag leaf length and width being responsible for the major differentiation. L. perenne separated into two groups following PCA, cluster analysis and k -means clustering, 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 be 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 introgression between them, especially between L. multiflorum and L. rigidum . The results are discussed in relation to selection of a core collection of Lolium accessions.