Beiträge zur Systematik und Biologie von Plectosphaerella cucumeris und der zugehörigen Konidienform

The ascigerous and conidial states of Plectosphaerella cucumeris Klebahn are redescribed. Perithecia were readily obtained only in four out of several thousand cultures. The species is homothallic. The correct name of the ascigerous state is considered to be Plectosphaerella cucumeris Klebahn; Nectria septomyxa Wollenweber is rejected, because it is based on a bitunicate ascomycete Sphaerella solani Ellis & Everh., for which the new combination Didymella solani (Ellis & Everh.) W. Gams & Gerlagh is proposed. For the identification of the conidial state the need for a ‘Hochkultur’ is emphasized. It is renamed Fusarium tabacinum (Beyma) W. Gams. A compilation of data has been made for the frequency of occurrence of the fungus in arable soils. The most significant observations on pathogenicity reported in the literature refer to tobacco and pansies. Own pathogenicity tests with potatoes, cucumbers, wheat, and rape were not successful. The most significant biological activities reported were xylan decomposition and steroid transformations.