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ESTABLISHMENT OF A WILD ROCKET (Diplotaxis tenuifolia) GERMPLASM
COLLECTION AND ITS PRELIMINARY ASSESSMENT FOR DOWNY MILDEW
RESISTANCE AND GENETIC DIVERSITY
Coelho, PS1; Carranca, C1; Scotti, P1; Semedo, J1; Loureiro, MF1; Pais, I1;
Gaspar, C2; Lopes, V2; António, C3; Diogo, V4; Leitão, J4
1INIAV, IP, Av. República, 2780-157 Oeiras, Portugal; 2BPGV/INIAV, S. Pedro de Merelim, 4700-859 Braga, Portugal;
3ITQB/NOVA, Av. República, 2780-157 Oeiras, Portugal; 4UAlg/FCT, Campus de Gambelas, 8005-139 Faro, Portugal
INTRODUCTION
RESULTS
Fig.1. Composition of the rocket
germplasm collection.
Biomolecular Characterization
Wild Rocket (Diplotaxis tenuifolia L.) is a baby leaf from Brassicaceae family, and its economic
relevance is increasing rapidly worldwide. Downy mildew (DM) caused by the oomycete
Hyaloperonospora sp. is a devastating disease, that reduces drastically the quality and yield of
the rocket leaves.
The aims of the project correspond to 4 scientific tasks: 1) Establishment of collections of
wild rocket germplasm and Hyaloperonospora sp. isolates; 2) Characterization of the rocket
collection regarding the response to DM infection under controlled and field conditions;
3) Biomolecular characterization of wild rocket and Hyaloperonospora sp. isolates; and
4) Metabolomic characterization of rocket with different DM responses.
Fig. 2. Preliminary evaluation of resistance response to downy mildew in rocket cotyledons, 1st and 2nd leaves accessions.
The accessions were divided in 4 groups according to DM resistance response: R=Resistant, PR=Partially Resistant,
S=Susceptible, and HS=Highly Susceptible.
•106 accessions were tested: Seed Banks=13, Breeding Companies=81, Commercial Varieties=3, and Eruca sp.=9.
Plants were inoculated by spraying with the Hyaloperonospora sp. isolate D5 at 15d, and were evaluated at 21d (Fig. 2).
• Cotyledons were more susceptible to DM than the 1st and 2nd leaves. Diplotaxis sp. showed different cotyledon and
leaves responses: 2acc. were cotyledon Resistant (from a Seed Bank and Breeding Company) and maintained a R leaf
response; 7acc. were cotyledon Partially Resistant and had a PR/R leaf response; 18 acc. were cotyledon Susceptible
and had a S/PR 1st leaf response; and 70 acc. were cotyledon Highly Susceptible, of which only 1 acc. was R (from a
Seed Bank), 11 acc. were PR, 39 acc. were S, and 19 acc. maintained the HS response on leaves (Fig. 2).
• All Eruca sp. (control) cotyledon and leaves inoculated with isolate D5 were Resistant.
•Genomic DNA was, so far, extracted from 40 D. tenuifolia accessions. A higher quantity of genomic DNA was extracted
from previously partially purified cell nuclei of a single plant and sent for next generation sequencing using an Illumina
platform.
• The bioinformatics analysis of the genomic and transcriptomic data available online (ncbi.nlm.nih.gov) allowed the
identification of 20 microsatellite loci among the uploaded Diplotaxis cDNA sequences (genomic data are still very scanty)
and 18 genomic microsatellite loci of Hyaloperonospora sp.
•Primers were obtained for all these loci and the respective microsatellite markers are presently being validated.
Hyaloperonospora sp. sporulation
on infected wild rocket (21d).
The first results regard the Establishment of the germplasm collection (Fig. 1), and the characterization of the
accessions to their Response to DM (Fig. 2) and Molecular features.
CONCLUSION
•In most accessions at 21 days evaluation, the 2nd leaf was very young and hence very resistant. The increase of
DM susceptibility with leaf aging was observed in other Brassica, such as cabbage, broccoli and radish.
Downy Mildew Response
This work is funded by national funds through the FCT - Foundation for Science and
Technology, I.P., in the context of the project «Refª PTDC/ASP-PLA/28963/2017».
cot.
cot.
1st leaf
2nd leaf