An efficient method for in vitro screening of susceptibility of wild cherry (Prunus avium L.) to Phytophthora species

A method was developed for in vitro screening clones of wild cherry (Prunus avium L.) for susceptibility to four Phytophthora species (P. uniformis, P. megasperma P. citrophthora, and P. cinnamomi), by using inoculation tests on micropropagated plants. Susceptibility was evaluated with a disease severity scale based on visual assessments of external symptoms. All tested wild cherry clones were very susceptible to P. citrophthora, while susceptibility to P. cinnamomi was variable among the clones, and resistance to P. uniformis and P. megasperma was generally high. These results were consistent with those obtained previously using inoculated wild cherry seedlings. The method offers advantages compared to seedling or sapling assays, including reduced time requirement, evaluation of cloned material under controlled conditions, and easy replication at any time of year. Compared to field tests, the method does not depend on the availability of land and does not involve risks of soil or water contamination, which is always a concern in Phytophthoras. The method is suitable for mass screening of plant material in programmes for selecting genetically improved wild cherry clones for disease resistance.