Screening and evaluation of resistance to downy mildew (Peronospora parasitica) and clubroot (Plasmodiophora brassicae) in genetic resources of Brassica oleracea

52 entries including landraces, old cultivars and wild accessions of B. oleracea and closely related Brassica species were screened for resistance against downy mildew and clubroot. Several accessions resistant to downy mildew and a few to clubroot were found. Genetic inheritance of the resistance in downy mildew was investigated by screening F1 and BC1F1 offspring from three resistant landrace accessions crossed with both a resistant and a susceptible father. The seedling resistance against downy mildew was found to be inherited recessively. This is a bit surprising as earlier papers mostly report of inheritance controlled by a single dominant gene. Previous screenings of B. oleracea resistance against downy mildew at the cotyledon stage have been done with P. parasitica isolated from B. oleracea as the original host plant. The recessive nature of the cotyledon resistance found in this screening might be due to the fact that the P. parasitica isolate was collected from B. napus fields. The clubroot seedling resistance was found to be controlled by recessive inheritance after screening the F1 offspring, this in agreement with earlier results/reports.