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Assessment of Wild Rocket (Diplotaxis tenuifolia (L.) DC.) Germplasm accessions by NGS identified SSR and SNP markers

Publication . Reis, João M.; Pereira, Ricardo; Coelho, Paula S.; Leitão, José

Rocket is the common designation for two baby-leaf salad crops of the Brassicaceae family: Eruca sativa (L.) Cav., usually referred to as annual garden rocket, and Diplotaxis tenuifolia (L.) DC. commonly named to as perennial wild rocket. E. sativa is used for human consumption since antiquity. However, the growing consumer preference for D. tenuifolia is being accompanied by the fast increase in its production area and commercialization of new cultivars. Nevertheless, the worldwide number of wild rocket accessions maintained in germplasm collections is very reduced, the solution for which situation the project “REMIRucula” intends to contribute, establishing a germplasm collection at the INIAV, Oeiras, Portugal. Herein, we report on the establishment via next generation sequencing (NGS) of the first genome assembly of D. tenuifolia and the identification of specific single sequence repeat (SSR) and single nucleotide polymorphisms (SNP) loci for the establishment of specific DNA-markers for this species. A representative set of 87 D. tenuifolia and 3 E. sativa accessions were assessed by 5 SSR and 9 SNP-CAPS markers, allowing a drastic discrimination between both species and the establishment of unequivocal molecular fingerprints for the analyzed accessions. The non-discrimination within six pairs and one trio of D. tenuifolia accessions is discussed.

2022-12-12Journal article

Open Access

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