Resistance toPhytophthora porri in leek and some of its wild relatives

Summary Winter leek and related plant material was evaluated for resistance to white tip disease (Phytophthora porri) in the Netherlands. Significant differences in partial resistance were found between winter leek accessions in field tests with zoospore and natural inoculation. These differences were consistent over three years, and indicate that resistance can be improved through mass selection in winter leek cultivars. Some accessions of wild or cultivated relatives of winter leek with higher levels of resistance were found in a glasshouse test with zoospore inoculation. These sources of resistance were also highly resistant in field experiments over a two year period.