|Rayas-Duarte, Patricia -|
|Mccullen, Michael -|
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 22, 2011
Publication Date: December 9, 2011
Citation: Doehlert, D.C., Rayas-Duarte, P., Mccullen, M.S. 2011. Inhibition of Fusarium graminiarum growth in flour gel cultures by hexane soluble compounds from oat (Avena sativa L.) flour. Journal of Food Protection. 74(12):2188-2191. Interpretive Summary: The plant disease commonly called “Scab” is caused by the fungus Fusarium graminearum, and primarily affects wheat and barley. Oats appear to be more resistant. This is generally attributed to the open panicle of oats, where the grain in oats is held on branches extending from the stem, rather than being clustered around the stem of the spike. However, we have investigated the possibility that chemical agents in oats may contribute to this resistance. We have grown the Fusarium fungus in culture plates on media made from the flour of wheat, barley and oats. Judging by colony diameter, the fungus grew better on wheat and barley flour than it did on oat flour. When we extracted fat from oat flour with hexane, the fungus grew just as well on defatted oat flour as it did on wheat flour. However, when we mixed the fat extracted from oats with wheat flour, we observed the same inhibition of fungal growth on the wheat flour with oat fat as we found with whole oat flour. We have identified oxygenated fats in oats that are associated with inhibition of fungal disease in rice and suspect these may be responsible for the inhibition of the fungal growth in culture. Our results support the possibility that oats may contain a chemical resistance to Fusarium, along with their open panicle.
Technical Abstract: Fusarium head blight, caused by the fungus Fusarium graminearum, primarily affects wheat (Triticum aestivum) and barley (Hordeum vulgarum) while oat (Avena sativa) appears to be more resistant. Although this has generally been attributed to the open panicle of oats, we hypothesized that a chemical component of oats may contribute to this resistance. To test this hypothesis, we created culture media made of wheat, barley, and oat flour gels (6 g flour/20 ml water, gelled by autoclaving) and inoculated these with plugs of Fusarium graminearum from actively growing cultures. Fusarium growth was measured from the diameter of the fungal plaque. Plaque diameter was significantly smaller on oat flour cultures than on wheat or barley cultures after 40 to 80 h of growth. Ergosterol concentration was also significantly lower in oat cultures than in wheat cultures after growth. A hexane extract from oats when added to wheat flour also inhibited Fusarium growth, and Fusarium grew better on hexane-defatted oat flours. The growth of Fusarium on oat flours was significantly and negatively affected by the oil concentration in the oat in a linear relationship. A hexane soluble chemical in oat flour appears to inhibit Fusarium growth and may contribute to oat’s resistance to Fusarium head blight. Oxygenated-fatty acids, including hydroxy, dihydroxy and epoxy fatty acids, were identified in the hexane extracts and are likely candidates for causing the inhibition.