Sources of resistance to stem nematode, Ditylenchus dipsaci (Kühn) Filipjev, in species of Medicago and Trifolium

The putatively resistant lucerne cv. Euver was as susceptible to 11 English and 11 French populations of ‘lucerne race’ stem nematode, Ditylenchus dipsaci, as the susceptible cv. Europe. The ‘resistant’ cv. Vertus showed some resistance to five of the English and four of the French populations but was just as susceptible as Europe to three English and four French populations. Twelve annual species of Medicago were very resistant to a mixture of two English and two French populations of the nematode. None of 13 perennial spp. of Medicago was very resistant to the same mixture of nematodes but resistant plants were identified in M. borealis, M. dzhawakhetica, M. glutinosa and M. romanica. Twenty six spp. of Trifolium were resistant to a mixture of two English and two French populations of ‘red clover race’ stem nematode.