Grundlagen für die biologische Bekämpfung von Rumex obtusifolius L. und R. crispus L. mit Uromyces rumicis (Schum.) Wint.

Abstract

TeUospores of Uromyces rumicis (Schum.) Wint., coUected in the field or in a greenhouse, are dormant. TeUospore dormancy could only be broken by an outdoor storage during the winter. TeUospores produced on detached dock leaves could be activated to germinate by storing the spores during 60 days on water agar at 2 °C in continuous darkness. Within ten days, after changing the teUospores to 8 °C or 15 °C under ulumination up to approximately 70 to 80% of the teliospores germinated with basidia and basidiospores. Both in the field experiment and in the climatic Chamber Ranunculus Fi¬ caria L. was the only species that could be infected by basidiospores (haplontic phase) of 17. rumicis. U. rumicis formed aecia and aeciospores on R. Ficaria. A reinfection of Rumex obtusifolius L. with the aeciospores was always successful. 11 species of the genus Ranunculus, 16 other species out of the famuy Ranunculaceae, Rumex crispus L., R. ob¬ tusifolius and Berberis vulgaris L. could not be infected. In the dicaryotic phase the pathogenicity of 11 strains of 17. rumicis was different. Strains coUected on R. obtusifolius infected R. obtusifolius and formed freely sporulating uredopustules. On the leaves of R. cris¬ pus the same strains caused only necrotic spots without uredopustules. Strains coUected on R. crispus produced freely sporulating uredopustu¬ les on R. obtusifolius and R. crispus. An american ecotype of R. cris¬ pus was not infected by aU strains of 17. rumicis coUected in the field. In the greenhouse uredopustules could be selected, which attacked this resistent ecotype severely.