A Narrow Range of Wavelengths Active in Regulating Apothecial Development in Sclerotinia sclerotiorum

Three Swedish and one Canadian isolate of Sclerotinia sclerotiorum were tested for apothecial formation in light of di€erent wavelengths and for measuring light absorbance of macerated apothecia and apothecia ®l- trate in a spectrophotometer. The apothecial formation was recorded after keeping laboratory-produced sclero- tia under di€erent light ®lters illuminated by True-Lite ¯uorescent tubes. The experiments, performed at room temperature, demonstrated that normal apothecia developed only in light of wavelengths between 276 and 319 nm, and that macerated apothecia and apothe- cia ®ltrate absorbed light at the same wavelengths with a maximum absorbance at 310 nm. The stipes showed a clear positive phototropism in light that was not essen- tial for apothecia development. indicating that there may be di€erent photoreceptors for phototropism and photomorphogenesis. Negative phototropism of stipes occurred at certain wavelengths in yellow light.