Differentiation of the physiological races of Peronospora valeria-nellae with a differential set of cultivars and RAPD-PCR

When cultivating Lamb's lettuce (Valerianella locusta), Peronospora valerianellae is causing significant economic losses. Like other downy mildews, Peronospora valerianellae forms physiological races. Nine isolates of Peronospora valerianellae were used for the infection of cultivars and breeding lines of Lamb's lettuce, different virulences could be identified. Based on the results of a set, consisting of six different compatible cultivars, five physiological races of the pathogen could be separated. Whilst carrying out the experiment, it was possible to develop RAPD-markers. The DNA extracted from sporangia was used for PCR with random primers. Five primers produced reproducible polymorphisms with which single races could be differentiated. In contrast to the inoculation method where five races were found, only four races could be identified using the RAPD-Markers.