Sources of resistance to downy mildew (Peronospora parasitica (Pers. (ex Fr.) Fr.) in Sicilian germplasm of cauliflower and broccoli

Downy mildew (Peronospora parasitica (Pers. ex Fr.) Fr.) is a serious disease of brassicas inseveral countries. Seedlings are very susceptible to this pathogen and crops require frequent fungicidetreatments to reach a good marketable yield. The use of resistant cultivars can be the most economical,reliable and environmental friendly method for managing this disease. In this work 32 Sicilian landracesand 16 commercial cultivars of cauliflower and broccoli (B. oleracea) were screened for downy mildewresistance at the cotyledon stage using one P. parasitica strain from Portugal and one from Sicily (Italy).Seven-day old seedlings were inoculated by deposing a droplet of a spore suspension on the cotyledons,incubated under controlled environment and scored 7 days later using a seven-class scale of interactionphenotype (IP), which took into consideration host response and pathogen sporulation. There were nodifferences in virulence between the two P. parasitica isolates. Accessions ranged from very susceptible tohighly resistant to downy mildew showing a variable number of resistant individuals per accession. Fortyaccessions were very susceptible to downy mildew and are of no interest as sources of resistance, sincemost of the seedlings were scored in the most susceptible IP classes. Seven accessions had intermediateresistance and included individuals that expressed some degree of resistance. Accession Cv 90 (‘CavolfioreTorino’) and Br 63 (‘Sparaceddu’) showed the majority of seedlings in the resistant IP classes andmay constitute valuable sources of resistance to downy mildew to be used in breeding programs.