Two key elements of the previous research effort were the availability of crop diversity collections from gene banks and a concerted effort to assemble extensive collec- tions of pathogen isolates, primarily from major crop production regions, in order to sample the diversity within the pathogen population.Indeed, one of the recommended downy mil- dew resistant lines (EBH502) was originally selected for white rust resistance in B. oleracea.Both elements were included in the current study, in an attempt to identify useful sources of downy mildew resistance for vegetable brassica production in the UK. A core diversity collection of more than 400 B. oleracea accessions had previously been screened for downy mildew resistance using two standard isolates of H. parasitica (Leckie et al., 1996).These were included in the current study because co-segregation of downy mildew resistance was observed following selection for white rust resistance in a rapid cycling population of B. rapa (Mitchell-Olds et al., 1995).Doubled haploid lines were also generated from white rust resistant plants selected in the earlier research effort.