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Submitted to: Aflatoxin Elimination Workshop Proceedings
Publication Type: Proceedings Publication Acceptance Date: 10/15/2002 Publication Date: 1/1/2003 Citation: Glenn, A.E. 2003. Panel discussion: fumonisin contamination of corn and development of cellular, biological, and enviromental control strategies. Aflatoxin Elimination Workshop Proceedings. October 23-26, 2001. Phoenix, Arizona. Interpretive Summary: The Second Fumonisin Elimination Workshop was once again held immediately prior to the Aflatoxin Elimination Workshop. The recent expansion of the workshop program to include fumonisins stems from food safety concerns associated with fumonisin contamination of corn. Such contamination results from pre-harvest fungal infection of corn, primarily by Fusarium verticillioides. This fungus is widely considered an endophyte of corn plants, is found world-wide wherever corn is grown, and is often the dominant fungus found infecting corn tissues, including kernels. Thus, given its close association with corn and its capacity to produce fumonisin mycotoxins, management strategies to eliminate, or at least significantly reduce levels of infection and production of fumonisins are of obvious concern. This is especially true given the recent release of FDA's "Draft Guidance for Industry" related to fumonisin levels in both human food and animal feed. Reflective of the growing interest in F. verticillioides and its processes of infection and fumonisin contamination of corn, this year's workshop program consisted of four presentations from ARS laboratories, three from university laboratories, and one from Monsanto Company. The presentations outlined the biological complexity of this fungus and its interactions with corn, while identifying potential strategies of control. A common theme emerging from the reports was the impact that environmental conditions can have on the severity of fumonisin production and contamination. Discussion began with a comment from Dr. Neil Widstrom concerning how current data suggest the environmental conditions are not as clearly defined as once thought. Defining specific seasonal parameters, for example temperature and rain (amount and timing), that result in high levels of fumonisin contamination is becoming more difficult since geographical location appears to have a significant impact. Overall fungal population structure, frequency of fumonisin-producing fungi in that population, and their inoculum levels were discussed as contributing factors in combination with environmental conditions. The discussion also focused quite heavily on the issue of some symptomless infections having significant levels of fumonisin contamination. Initial discussion focused on whether such symptomless contamination was simply a fluke or perhaps a subject of considerable concern. If symptomless contamination is found to be a consistent phenotype, what are the factors contributing to mycotoxin production? Fungal biomass within corn tissues was discussed relative to its metabolic activity and interactions with the corn host. Identification and utilization of resistant genetic corn stock were stressed as objectives necessary for management and control of Fusarium infection, ear rot development, and fumonisin contamination, especially given the close association between corn and the endophytic F. verticillioides. Also discussed was plant gene expression in response to environmental stresses and how F. verticillioides is in turn responding. Does the fungus respond to a stressed host plant in such a way to benefit itself, or does the fungus also suffer stress and therefore responds to alter its own microenvironment? How would either response impact mycotoxin production? Clearly much can still be learned about the interactions of F. verticillioides with its host and the impact of environmental conditions. Such knowledge in combination with resistance corn lines could greatly facilitate management of fumonisin contamination. Technical Abstract: The Second Fumonisin Elimination Workshop was once again held immediately prior to the Aflatoxin Elimination Workshop. The recent expansion of the workshop program to include fumonisins stems from food safety concerns associated with fumonisin contamination of corn. Such contamination results from pre-harvest fungal infection of corn, primarily by Fusarium verticillioides. This fungus is widely considered an endophyte of corn plants, is found world-wide wherever corn is grown, and is often the dominant fungus found infecting corn tissues, including kernels. Thus, given its close association with corn and its capacity to produce fumonisin mycotoxins, management strategies to eliminate, or at least significantly reduce levels of infection and production of fumonisins are of obvious concern. This is especially true given the recent release of FDA's "Draft Guidance for Industry" related to fumonisin levels in both human food and animal feed. Reflective of the growing interest in F. verticillioides and its processes of infection and fumonisin contamination of corn, this year's workshop program consisted of four presentations from ARS laboratories, three from university laboratories, and one from Monsanto Company. The presentations outlined the biological complexity of this fungus and its interactions with corn, while identifying potential strategies of control. A common theme emerging from the reports was the impact that environmental conditions can have on the severity of fumonisin production and contamination. Discussion began with a comment from Dr. Neil Widstrom concerning how current data suggest the environmental conditions are not as clearly defined as once thought. Defining specific seasonal parameters, for example temperature and rain (amount and timing), that result in high levels of fumonisin contamination is becoming more difficult since geographical location appears to have a significant impact. Overall fungal population structure, frequency of fumonisin-producing fungi in that population, and their inoculum levels were discussed as contributing factors in combination with environmental conditions. The discussion also focused quite heavily on the issue of some symptomless infections having significant levels of fumonisin contamination. Initial discussion focused on whether such symptomless contamination was simply a fluke or perhaps a subject of considerable concern. If symptomless contamination is found to be a consistent phenotype, what are the factors contributing to mycotoxin production? Fungal biomass within corn tissues was discussed relative to its metabolic activity and interactions with the corn host. Identification and utilization of resistant genetic corn stock were stressed as objectives necessary for management and control of Fusarium infection, ear rot development, and fumonisin contamination, especially given the close association between corn and the endophytic F. verticillioides. Also discussed was plant gene expression in response to environmental stresses and how F. verticillioides is in turn responding. Does the fungus respond to a stressed host plant in such a way to benefit itself, or does the fungus also suffer stress and therefore responds to alter its own microenvironment? How would either response impact mycotoxin production? Clearly much can still be learned about the interactions of F. verticillioides with its host and the impact of environmental conditions. Such knowledge in combination with resistance corn lines could greatly facilitate management of fumonisin contamination. |
