Impact of essential oils on growth rate, zearalenone and deoxynivalenol production by Fusarium graminearum under different temperature and water activity conditions in maize grain.

AIMS: The effect of five essential oils (oregano, cinnamon, lemongrass, clove and palmarose) on growth rate, zearalenone (ZEA) and deoxynivalenol (DON) production by Fusarium graminearum strains was assessed. METHODS AND RESULTS: The influence of the essential oils was tested on irradiated maize at two concentrations (500 and 1000 mg kg-1), at different water activity (aw) (0.95 and 0.995) and temperature (20 and 30 degrees C) levels. At 0.995 aw all essential oils tested had an inhibitory effect on growth rate of F. graminearum at both temperatures studied. At this aw level, DON production in general was inhibited by all essential oils at 30 degrees C and, although palmarose and clove were the only essential oils with statistically significant inhibitory effect on ZEA production, an inhibitory trend was observed when cinnamon and oregano oils were added to maize grain. CONCLUSIONS: Antifungal and antimycotoxigenic activity of the essential oils assayed was shown to depend on environmental conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: It is apparent that essential oils should be considered as alternative preharvest natural fungicides. Further investigation on natural maize grain might be useful to study the effectiveness of these essential oils in the presence of natural mycoflora of maize grain.

Inhibitory effect of cinnamon, clove, lemongrass, oregano and palmarose essential oils on growth and fumonisin B1 production by Fusarium proliferatum in maize grain.

The effect of cinnamon, clove, oregano, palmarose and lemongrass oils on growth and FB1 production by three different isolates of F. proliferatum in irradiated maize grain at 0.995 and 0.950 aw and at 20 and 30 degrees C was evaluated. The five essential oils inhibited growth of F. proliferatum isolates at 0.995 aw at both temperatures, while at 0.950 aw only cinnamon, clove and oregano oils were effective in inhibiting growth of F. proliferatum at 20 degrees C and none of them at 30 degrees C. Cinnamon, oregano and palmarose oils had significant inhibitory effect on FB1 production by the three strains of F. proliferatum at 0.995 aw and both temperatures, while clove and lemongrass oils had only significant inhibitory effect at 30 degrees C. No differences were found using 500 or 1000 microg essential oil g(-1). At 0.950 aw, none of the essential oils had any significant effect on FB1 production. The results suggest that mainly cinnamon and oregano oils could be effective in controlling growth and FB1 production by F. proliferatum in maize under preharvest conditions.

The effect of fungal competition on colonization of maize grain by Fusarium moniliforme, F. proliferatum and F. graminearum and on fumonisin B1 and zearalenone formation.

The effect of water activity (0.98, 0.95, 0.93) and temperature (15, 25 degrees C) on fungal growth and toxin production from interactions between isolates of Fusarium moniliforme and F. proliferatum producing fumonisin, and an isolate of F. graminearum producing zearalenone, incubated at the same time on irradiated maize grains were determined in vitro. Populations (CFUs) of F. moniliforme and F. proliferatum were reduced to a greater or lesser extent by the presence of F. graminearum under all conditions tested, while that the presence of F. moniliforme or F. proliferatum had a minor inhibitory effect on fungal populations of F. graminearum. Fumonisin B, production by F. proliferatum was inhibited under all conditions tested, while fumonisin B1 production by F. moniliforme was inhibited at 15 degrees C and enhanced at 25 degrees C in the presence of F. graminearum. The level of zearalenone was not significantly modified in the presence of F. moniliforme and F. proliferatum under the conditions tested.