EVALUATION OF A LUCERNE GERMPLASM COLLECTION IN RELATION TO TRAITS CONFERRING GRAZING TOLERANCE

A collection of 90 accessions of different germplasm groups from the M edicago sativa complex was evaluated at Lodi, Italy, for dry-matter yi eld, time to anthesis, height of regrowth, plant diameter, stem densit y, vegetative recovery after winter, and presence of deep-set crown an d ability to spread with creeping roots or rhizomes, these latter char acters possibly contributing to grazing tolerance. The germplasm group s proved rather distinct for these traits, but all included types pote ntially suitable for grazing. Interesting types combining deep-set cro wn and high yield occurred mainly in subsp, x varia and materials orig inated from artificial crosses involving at various extent the subspec ies falcata, sativa and x varia. Though belonging to subsp. sativa, '' mielga'' wild populations from Spain had aerial traits similar to thos e of the long-dormant, low-yielding subsp. falcata. Deep-crowned plant s had greater plant diameter than shallow-crowned plants, and could be categorised into four distinct top-growth models according to their h abit and vigour. One of these models combined spreading ability with h igh yield. The about 150 plants selected for their combination of deep crown, wide diameter, and good yield were characterised by a branch-r ooted system. There was general correspondence between top-growth and root morphology of each model. Of the four deep-crowned models, three had rhizomes, with wide range of underground development and morpholog y, while the fourth had creeping roots. The latter model was the most rare among the examined accessions, never appearing in either cultivat ed or wild subsp, sativa. The implications of the results on the devel opment of grazing-tolerant lucerne varieties are discussed.