Action Spectrum for Photosporogenesis in Botrytis cinerea Pers. ex Fr

An action spectrum for photoinduced conidium formation in the fungus Botrytis cinerea Pers. ex Fr. was determined by exposing colonies to monochromatic radiation obtained from a diffraction grating monochromator. Wavelengths longer than 355 nm were ineffective even after exposures of 8 hours at intensities of 4,068 to 8,276 erg per cm(2) per second. Colonies were exposed at 22.5 C from 226 to 355 nm at about 5 nm intervals. Three prominent peaks of effectiveness occurred at about 231, 268, and 283 nm, and there was also a minor peak at about 303 nm. The most effective wavelength for inducing sporulation was 231 nm; it was 25% more effective than the second most effective wavelength (283 nm).