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Beschreibung:
The obligate biotrophic soil-borne fungus Synchytrium endobioticum is the causal agent of potato wart disease and is classified as a quarantine pest by the European and Mediterranean Plant Protection Organization. It produces sporangia with several hundred motile zoospores which infect meristematic tissue of below-ground parts of the plants, like tubers, stolons and stems of the potato, causing yield losses of up to 50-100 %. Typical symptoms are the formation of cauliflower-like irregular galls on the below-ground parts of the plant. The thick-walled resting sporangia are able to survive in the soil for several decades. More than 40 different pathotypes of S. endobioticum have been described. Pathotypes 1, 2, 6 and 18 are the most common and most aggressive forms of the fungus in Europe. Chemical control is difficult because accessibility of winter sporangia is limited and chemicals cannot penetrate the thick walls of the sporangium. Chemicals reported to be effective against S. endobioticum have also been described as phytotoxic and harmful to the environment. Strict phytosanitary measures and breeding of resistant potato cultivars are currently the methods of choice to control the disease. Another difficulty is the phenotypic resistance assessment of potato cultivars. To determine the resistance approximately 20 tubers have to be inoculated per pathotype and genotype, which are then evaluated microscopically and assigned to different resistance classes, ranging from extremely resistant to extremely susceptible. These amounts of tubers become available only after several years within the breeding process. Molecular markers that could detect resistant genotypes early in the breeding process, independently of the availability of tubers, would greatly facilitate breeding of potato wart resistant cultivars. Several resistance loci have been identified on different potato chromosomes with different resistance loci dependent on the genetic background of the used plant material. One major resistance locus has been ...