Screening for resistance to downy mildew and its early detection in roses

authored by
D. F. Schulz, T. Debener
Abstract

A resistance screening method was developed with defined conidia concentrations of Peronospora sparsa in a detached leaf assay. Disease severity was estimated microscopically by a five-step classification scheme based on the production of conidophores on the lower side of the leaf. With this method, a resistance screening was performed among several wild rose accessions and garden rose cultivars and 13 highly resistant accessions could be identified, which only occur among wild species. These accessions can be used to introgress resistance genes into breeding material. For the early detection of P. sparsa, a highly sensitive PCR based detection method was developed based on published primers and specific primers based on genomic DNA of P. sparsa after random priming with 34 different 15 to 20 meres. With the published ITS specific primers, we could detect pathogen DNA at a concentration of about 0.1 pg with primer PS 1/3. With primer PR 3/4, the sensitivity was tenfold higher but the specificity was lower. With our own designed specific primers, we could demonstrate in first tests that they could be useful for the detection of downy mildew in leaf samples. An ELISA using polyclonal antisera against P. sp a r s a was established as the second approach to detect the pathogen in the plant. It allows also the quantification of the pathogen. The detection limit for protein of P. sparsa in rose leaf extract was estimated at 10 ng/ml. The visual- and the serological detection methods were used in parallel to compare the correlation between the symptomatic leaf area and the ELISA readings in field-infested plants. A strong correlation was found between the infestation of the leaves and the protein content of P. sparsa.

Organisation(s)
Faculty of Natural Sciences
Section Molecular Plant Breeding
Type
Article
Journal
Acta Horticulturae
Volume
751
Pages
189-198
No. of pages
10
ISSN
0567-7572
Publication date
2007
Publication status
Published
Peer reviewed
Yes
ASJC Scopus subject areas
Horticulture
Electronic version(s)
https://doi.org/10.17660/ActaHortic.2007.751.22 (Access: Unknown)