Downy mildew resistance and genetic variability in a wild rocket germplasm collection

Abstract

One hundred accessions of a “core collection” of Diplotaxis tenuifolia (L.) DC. and Eruca spp. were screened at seedling stage for resistance to downy mildew. Accessions tested at the seedling stage were assigned to 0–6 interaction phenotypes. All cultivated rocket (Eruca spp.) accessions exhibited a resistant (R) response both in cotyledons and in young leaves. The wild rocket (D. tenuifolia) accessions exhibited higher susceptibility in cotyledons than in the 1st and 2nd leaves, with 16 and 47 accessions classified as resistant or partially resistant (PR) in the cotyledon and in leaves stages, respectively. Only three wild rocket accessions displayed an R phenotype in cotyledons and leaves. The most frequent response in cotyledons vs. leaves was the highly susceptible/susceptible (HS/S) combination (33 accessions), followed by the S/PR combination (18 accessions). A significant correlation (r = 0.917, P