GREEN-IT "Bioresources for Sustainability"

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

Publication . Coelho, Paula S.; Reis, João M.; Pereira, Ana L.; Vairinhos, Aliana; Lopes, Violeta; Leitão, José

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 < .000) was observed between the disease index in cotyledons and leaves. The molecular markers analyses revealed a wide genetic distance between Diplotaxis and Eruca, which gather in two clearly separated species clusters. The molecular variability is accompanied by a wide diversity of interactions with the pathogen isolate. The closest similarities among D. tenuifolia accessions were found in accessions provided by the same breeding company. Future studies will be focused on two main objectives: (a) the assessment of the accessions behavior that have evidenced an R/R, S/PR, and HS/PR cotyledon and leaf response under greenhouse or field production and (b) the genome mapping of genetic features that provide downy mildew resistance.

2022Journal article

Open access

Downy mildew evaluation in wild rocket genotypes (Diplotaxis tenuifolia (L.) DC) under field and controlled conditions

Publication . Coelho, P. S.; Pereira, A. L.; Reis, João; Carranca, C.; Lopes, V. R.; Leitão, José

Wild rocket downy mildew (DM) is a foliar disease caused by the oomycete Hyaloperonospora spp. that limits the production of brassicas, especially in temperate climates, infecting plants at all growth stages. During 2021 autumn season, a field trial (polytunnel) with a set of 40 wild rocket accessions from different origins (harvest missions, gene banks, commercial cultivars) was installed in a commercial enterprise located in Odemira, southern Portugal. The plants were naturally infected by Hyaloperonospora spp. and were visually evaluated 71 days after sowing. Field observations of adult plants evidenced differences among accessions concerning the DM resistance and agronomic traits (e.g., flowering date, vigour, plant habit, leaf serration). Sixteen wild rocket accessions were identified with an interesting resistance response to DM in adult phase. In a previous study, the wild rocket accessions were tested to Hyaloperonospora isolate D5 at seedling stage under controlled conditions. A significant coefficient of correlation was observed (r=0.628, P=0.000, n=36) by comparing the plants in both growth phases. In general, the accessions were more resistant at adult than at seedling stage. No accessions were resistant at seedling and susceptible at adult stage. However, two accessions with a highly susceptible response at seedling stage presented a resistant and a partially resistant response at adult phase under field conditions. Our results suggest that DM resistance observed at the seedling stage is a good indication of wild rocket resistance behaviour at field adult plant. The most promising accessions identified as resistant at seedling stage may be further exploited in breeding programmes.

2023-10Conference object

Restricted access