Fumonisin content in conventional versus Bt maize and implications of fumonisin contamination on fuel ethanol yield and DDGS quality

Abstract

Genetic engineering of maize plants with genes (Bt genes) for resistance to Lepidopteran insects reduces the risk of grain contamination with fumonisin mycotoxins. Fumonisins are secondary metabolites of certain Fusarium fungal species that may be present in maize grain and, when consumed, lead to a variety to detrimental health impacts in both humans and animals. Changing insect populations, newly available transgenes, and trends in maize utilization have raised new questions about the scope of Bt effects on fumonisins. Field trials were conducted at two locations in 2008-2011 to assess the effects of expression of Bt insecticidal proteins Cry1Ab, Cry1F, or Cry1Ab x Vip3Aa on fumonisin contamination in grain following infestations with European corn borer (ECB), Western bean cutworm (WBC), corn earworm (CEW), and natural insect infestation (no insects applied). These maize pests are common in the major maize-producing regions of the United States and their feeding can reduce yields and increase levels of fungal contamination and mycotoxins. Fumonisins have also demonstrated toxic effects on certain yeast strains used in fermentation of maize grain for fuel ethanol production. Additionally, because fumonisins are heat-stable and non-volatile under relevant conditions, they can be enriched up to threefold in dried distillers’ grains with solubles (DDGS), the residual non-fermentable co-product of fuel ethanol processing which is fed to livestock. Therefore, fumonisin contamination in maize is a significant consideration for maize and maize-based ethanol producers. Grain quality was assessed by visual inspection to determine the extent of kernel injury and Fusarium ear rot, and by ELISA or HPLC to determine the fumonisin content. Visual assessment of maize obtained from field trials revealed significant reductions in kernel injury and Fusarium ear rot in Bt versus non-Bt maize. Both HPLC and ELISA