Effects of blue and near ultraviolet lights on the lateral-type sclerotial development in Botrytis cinerea were studied.
When a developing sclerotial primordium at a stage from 2 (i.e. swelled hyphae) to 3 (i.e. club-shaped hyphae) was exposed to blue light for 12-24hr, sclerotial development was inhibited. The outgrowth of club-shaped hyphae from swelled ones and further branching of club-shaped hyphae were suppressed and these sclerotial initials de-differentiated into “sterile” hyphae with sharply pointed and shrivelled tips. The inhibitory effect of blue light on the primordia at a stage from 2 to 3 could not be reversed by near ultraviolet light.
On the other hand, when a sclerotial primordium at a stage from 1 to 3 was exposed to near ultraviolet light for a short time, the formation of conidiophores was induced on that primordium. Sclerotial development was inhibited by the predominance of conidiation over the sclerotial primordia at a stage from 1 to 2. The sclerotial development after stage 3 was no longer influenced by irradiation with near ultraviolet light, and continued normally.
Thus, both blue and near ultraviolet lights inhibited the lateral-type sclerotial development at a definite stage of sclerotial formation, though the effects of these lights were different from each other.