Comparison of botanical characteristics and seedling root fluorescence fordistinguishing Italian and perennial ryegrass

The seedling root fluorescence test is used by many seed regulatory agencie s to distinguish between Italian (Lolium multiflorum Lam.) and perennial (L . perenne L.) ryegrass seeds. The objectives of this study were to examine phenotypic differences between fluorescent and non-fluorescent Italian and perennial ryegrass plants, and to compare classification of Italian and per ennial ryegrass using either seedling root fluorescence or botanical charac teristics. Fourteen populations were generated by dividing four Italian and three perennial ryegrass cultivars into fluorescent and non-fluorescent po pulations. Populations were evaluated for leaf color, growth habit, leaf ve rnation (rolled or folded), leaf width, and leaf length in the greenhouse a nd field. Plant height, spike length, spikelets spike(-1) and florets spike let(-1) were also measured in the field. Populations differed significantly for all characteristics. Population means and generalized squared distance s between populations for botanical characteristics were not significantly different for fluorescent and non-fluorescent populations within a given cu ltivar. Seedling root fluorescence was not linked to species or botanical c haracteristics. Stepwise discriminant analysis indicated that the rolled le aves oft. multiflorum discriminated it from L. perenne which has folded lea ves. Discrimination based on leaf vernation alone was identical to that usi ng all botanical characteristics and root fluorescence. A test based on lea f vernation should offer more reliable results than the seedling root fluor escence test for distinguishing Italian and perennial ryegrass.