THE PLANT-GROWTH REGULATOR METHYL JASMONATE INHIBITS AFLATOXIN PRODUCTION BY ASPERGILLUS-FLAVUS

Aflatoxins are highly toxic and carcinogenic compounds produced by cer tain Aspergillus species on agricultural commodities. The presence of fatty acid hydroperoxides, which can form in plant material either pre harvest under stress or postharvest under improper storage conditions, correlates with high levels of aflatoxin production. Effects on funga l growth and aflatoxin production are known for only a few of the nume rous plant metabolites of fatty acid hydroperoxides. Jasmonic acid (JA ), a plant growth regulator, is a metabolite of 13-hydroperoxylinoleni c acid, derived from alpha-linolenic acid. The volatile methyl ester o f JA, methyl jasmonate (MeJA), is also a plant growth regulator. In th is study we report the effect of MeJA on aflatoxin production and grow th of Aspergillus flavus. MeJA at concentrations of 10(-3)-10(-8) M in the growth medium inhibited aflatoxin production, by as much as 96%, Exposure of cultures to MeJA vapour similarly inhibited aflatoxin prod uction. The amount of aflatoxin produced depended on the timing of the exposure. MeJA treatment also delayed spore germination and inhibited the production of a mycelial pigment. These fungal responses resemble plant jasmonate responses.