7 months ago


Poster 15 Natural

Poster 15 Natural Products to control black dot and silver scurf in Potatoes Josep Massana Codina 1,2 , Sylvain Schnee 1 , Brice Dupuis 1 , Stéphanie Schürch 1 , Jean- Luc Wolfender 2 and Katia Gindro 1 1 Agroscope, Nyon, 2 Université de Genève, Genève, Black dot and silver scurf are two blemish diseases of Solanum tuberosum L. These two diseases affect the quality of the tubers and are caused by two phytopathogenic fungi: Colletotrichum coccodes and Helminthosporium solani, respectively. Chemical fungicides are commonly used to control fungal pathogens, but this is not an option in consumption potatoes because of the residues remaining on tubers. Natural Products (NPs) are chemical compounds or substances that are produced by a living organism: this definition encompasses both complex extracts, but also the isolated compounds of these extracts, and they can be produced by marine organisms, bacteria, fungi or plants. The use of Natural Products (NPs) as source of antifungal compounds has been largely used in the past years. This strategy offers several advantages in comparison to the traditional chemical control. First of all, few active ingredients are available in the chemical control fungicides, increasing the risk of resistance development; second, residues of these compounds can be found on the surface of the food products, with a potential effect on public health; and finally, the use of synthetically produced antifungal compounds for the treatment of food products induces concern in consumers. The aim of this project is to use NPs for post-harvest treatments of potato tubers in order to control the blemish diseases black dot and silver scurf. To this end, (1) plant species from different families showing diverse secondary metabolite production were selected; (2) different extracts from these plants were produced; (3) their biological activity was evaluated through a newly developed in vitro biotest; (4) the activity of some of these extracts is currently tested in vivo; and (5) the active compound will be isolated and characterized. In total, more than 50 extracts from 21 plant species were screened for a biological activity against Colletotrichum coccodes and Helminthosporium solani. Some of these extracts showed antifungal activity to one of the fungal pathogens, but only three of them showed antifungal activity against both. These three plant extracts were selected for further experiments, including the isolation of the active compound and the treatment of infected tubers. Preliminary data show interesting results that need to be confirmed. The use of efficient NPs to treat potato tubers against C. coccodes and H. solani, appears then as a promising alternative. 22

Poster 20 Developing a fast, accurate and cost-saving technique to determine the vegetative compatibility types in Cryphonectria parasitica Sever Branka, Carolina Cornejo, Daniel Rigling, Simone Prospero WSL, Zürcherstrasse 111, 8903 Birmensdorf, Hypovirus infection of the chestnut blight fungus Cryphonectria parasitica attenuates virulence on chestnut trees. However, vegetative incompatibility restricts virus transmission and hampers biological control of chestnut blight. To date, the vegetative compatibility (vc) types in C. parasitica are determined by pairing the target isolates with tester strains of known vc types. This method is, however, time consuming and not always completely reliable. Our main goal was to develop a multilocus genotyping assay to characterize the vegetative incompatibility (vic) loci in C. parasitica. A new primer set was developed that characterizes the six known di-allelic vic loci. Primers were labeled with fluorescent dyes for detection on a genetic analyzer. PCR assay results were validated using a panel of European tester strains with genetically determined vic genotypes. We are currently verifying the PCR specificity and optimizing the multilocus assays. 23

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