Suppressive effect of preirradiation with blue light on near ultraviolet light induced conidiation in Alternaria tomato

Abstract

Conidiophore formation in Alternaria tomato (Cke.) Weber (ATCC 38852) was induced by irradiation with near ultraviolet light, and conidia formed in subsequent darkness. However, blue light applied before the inductive near ultraviolet radiation suppressed the induction. Preirradiation with blue light just before the inductive near ultraviolet radiation was most suppressive. An action spectrum for this suppression showed a peak around 447 nm, with a shoulder between 400 and 440 nm, a minor peak around 478 nm in the blue region, and another near 385 nm in the near ultraviolet region. This action spectrum is very similar to the ubiquitous blue light response (cryptochrome).