A narrow range of wavelengths active in regulating apothecial development in Sclerotinia sclerotiorum

Three Swedish and one Canadian isolate of Sclerotinia sclerotiorum were tes ted for apothecial formation in light of different wavelengths and for meas uring light absorbance of macerated apothecia and apothecia filtrate in a s pectrophotometer. The apothecial formation was recorded after keeping labor atory-produced sclerotia under different light filters illuminated by True- Lite fluorescent tubes. The experiments, performed at room temperature, dem onstrated that normal apothecia developed only in light of wavelengths betw een 276 and 319 nm, and that macerated apothecia and apothecia filtrate abs orbed light at the same wavelengths with a maximum absorbance at 310 nm. Th e stipes showed a clear positive phototropism in light that was not essenti al for apothecia development. indicating that there may be different photor eceptors for phototropism and photomorphogenesis. Negative phototropism of stipes occurred at certain wavelengths in yellow light.