Production of alternariol and alternariol methyl ether by Alternaria alternata grown on fruits at various temperatures

Two toxigenic strains of the fungus Alternaria alternata (ATCC 56836 and ATCC 66868) were grown on surface-disinfected, fresh, ripe fruits and tested for the production of alternariol (AOH) and alternariol methyl ether (AME). Examined fruits included strawberries; red and green seedless grapes; concord grapes; red delicious, golden delicious, and gala apples; and blueberries. After inoculation, fruits were incubated at 4, 10 degrees C, or room temperature (approximately 21 degrees C) for up to 3 weeks. At weekly intervals, duplicate samples were analyzed for AOH and AME by using liquid chromatography. Results indicated that A. alternata and its metabolites were not a major problem in strawberries due to the presence of fast-growing molds like Rhizopus and Botrytis that outgrew and possibly inhibited Alternaria. Both Alternaria strains showed limited growth on apples, although fast-growing molds were not present after surface disinfection; AOH and AME were produced only by the ATCC 56836 strain on the golden delicious and gala varieties, (ranging from <0.1 to 5 microg/g and <0.1 to 14 microg/g for AOH and AME, respectively). Restricted growth of both strains without toxin production occurred in blueberries, whereas moderate growth and AOH (<0.1 to 3,336 microg/g) and AME (<0.1 to 1,716 microg/g) production took place in grapes.