Blue light inhibits mycotoxin production and increases total lipids and pigmentation in Alternaria alternata.

Light inhibits production of the mycotoxins alternariol and alternariol monomethyl ether, both polyketids produced by Alternaria alternata. This effect seems to be general because seven isolates of A. alternata with different alternariol- and alternariol monomethyl ether-producing abilities all respond to continuous light with reduced levels of alternariol and alternariol monomethyl ether when the mycotoxins were calculated on a microgram-per-milligram (dry weight) basis. Blue light inhibited alternariol and alternariol monomethyl ether production 69 and 77%, respectively. Red light gave no reduction of toxin levels. Total lipids were increased 25% when mycelium was grown in blue light as compared with red light or darkness. In white or blue light, but not in red light or darkness, a red-brown pigment accumulated by the mycelium.