Lettuce (Lactuca sativa) is an important leafy vegetable, most often used in salads. A significant yield and quality constraint in lettuce cultivation is the downy mildew pathogen Bremia lactucae. Downy mildew (Dm) resistance genes  introgressed in lettuce cultivars are often rapidly broken by new Bremia strains. As such, there is a constant need to identify new resistance gene variants that can be used in lettuce breeding programmes.

Wild Lactuca germplasm is suggested to contain a large diversity of field-evolved resistance against diverse Bremia pathotypes. Although the genetic basis of several Dm resistance genes have been unravelled, few information is known on the frequency and variation of these genes in natural populations. Our research aims to assess the genetic diversity of Dm resistance genes in populations of wild lettuce species in order to improve germplasm exploration strategies and resistance breeding in lettuce.