Het toetsen van stammen vanNectria cinnabarina (Tode) fr. op levende takken in vitro

Summary Some types of elm hybrids resistent to the Dutch elm disease turned out to be susceptible toNectria cinnabarina (Tode) Fr. This fungus may behave as a parasite, killing branches. Virulent and non-virulent strains are known. A method is described for cultivatingNectria-strains in vitro on living desinfected branches ofAcer and ofUlmus. Three weeks after inoculation with a virulent strain the branches were killed. They were covered all over by a thick layer of mycelium. The mycelium of non-virulent strains could not kill the branches. It developed only sparsely. By this method it will be possible to select the most virulent strains out of a collection of isolates in order to use them for testing elm hybrids on their resistence toNectria cinnabarina.