Identification, occurrence and host range of tomato powdery mildew (Oidium lycopersici) in the Czech Republic.
A powdery mildew (Oidium lycopersici) was recorded on tomato (Lycopersicon esculentum) for the first time in 1988 in the Czech Republic. Since that time, regular occurrence of spontaneous infection on leaves of glasshouse-grown tomatoes has been observed in at least 8 localities in the Czech Republic. Only the conidial (anamorph) stage was recorded; no sexual stage was found. For this reason a complete taxonomic determination was not possible. Morphological characterization confirmed that the observed powdery mildew could be described as Oidium lycopersici. In host-range studies 70 species of 20 genera of Solanaceae and 7 species of Cucurbitaceae were tested under controlled conditions with one isolate of O. lycopersici. Most of the Solanaceae expressed resistant or moderately susceptible reactions. A high level of susceptibility was recorded only in some Solanum species (S. capsicoides, S. jamaicense, S. laciniatum and S. lycopersicoides). On some Cucurbitaceae (Cucumis melo, C. sativus, Cucurbita spp.) development of powdery mildew symptoms and sporulation were recorded.