Saatgut-Testmethoden für Falschen Mehltau an Feldsalat

Peronospora valerianellae is one of the most important pathogens of corn salad. It is seedborne and besides seed treatments there is no possibility to control the disease. The wash-off-test and the grow-out-test are currently in use to test seed lots for the presence of the pathogen. Despite these test methods, there are still seed lots that show infected plants during production of corn salad. This indicates that a low infection rate of a seed lot (< 0.25% - 1%) may lead to serious problems in grower’s production units. To allow an improved identification of seed lots with low infection rate, a specific PCR-based detection method for P. valerianellae was developed. Three test methods were compared for their efficacy to detect contaminated seed lots. Six out of seven seed lots not showing contamination in the standard grow-out test were identified as contaminated. With an extended grow-out test, it was possible to confirm these results from the PCR-test. The PCR based test for P.valerianellae on seed offers the possibility to detect the pathogen below the actual detection limits.