Research Accomplishment Reports 2011

Mycotoxins: Biosecurity, Food Safety and Biofuels Byproducts (NC129, NC1025)

L.J. Vaillancourt
Department of Plant Pathology

 

Non-Technical Summary

One of the most important food safety and security issues facing grain and livestock producers is preventing mycotoxin contamination of food and feed, and reducing the deleterious effects of mycotoxins on livestock. Mycotoxins in grains processed for biofuels become concentrated in the solid byproduct known as distillers grain (DG). The sale of DGs for animal feed has become an important source of supplemental income for biofuel producers, and mycotoxin contamination is a major concern.

The lowering of tolerance limits for mycotoxins in overseas markets has increased the burden for grain buyers and food processors; currently, levels of mycotoxins that are acceptable for some US products are unacceptable in European and Asian markets, resulting in non-tariff trade barriers. Grain buyers and food processors need a reliable method for rapid assessment of grain quality pertaining to mycotoxins and mycotoxigenic fungi.

One important objective of this project is to develop and test rapid methods based on molecular diagnostic techniques to detect mycotoxins at the first points of sale (elevators), as well as mycotoxigenic fungi in the commodity. The project also aims to develop and test several novel cost-effective protocols to detoxify mycotoxins and prevent further deterioration in contaminated grain. New methods to monitor and treat contaminated grain would benefit domestic consumers and would allow American commodities to compete more effectively in foreign markets.

Another objective of the project is to characterize the genetic and environmental factors that influence production of mycotoxins. This information will enable us to improve our ability to predict, monitor, and minimize mycotoxin production in the field. Workers who are responsible for animal and human health need information about the toxicity, carcinogenicity, modes of action, and biomarkers of exposure and disease for all categories of mycotoxins. To address this need, this project also includes research in these areas that can be used to train health-care providers to identify exposure and treat related disease, as well as to develop accurate risk assessment recommendations.

2011 Project Description

We are working to understand molecular relationships among mycotoxigenic fungi, and genes that quantitatively regulate pathogenicity and mycotoxin biosynthesis, with a focus on the Fusarium pathogens that cause Fusarium head blight (FHB) of wheat and barley. FHB results in contamination of grain with tricothecene mycotoxins, which are severely damaging to human and animal health, and which pose significant regulatory constraints to the producer.

A combination of host resistance and fungicide treatment is the most effective strategy to lower the impact of FHB. To produce cereal varieties with durable resistance, and to maintain efficacy of fungicide treatments, we must understand the origin and degree of genetic diversity that is present in the pathogen population.

In one part of our recent work we developed new genetic markers that can be used to monitor out-crossing and genetic diversity in the pathogen population. Application of these novel repetitive RFLP probes to a group of G. zeae isolates originating in and near Kentucky uncovered a surprisingly high degree of genotypic diversity in these local populations. It confirmed that the isolates used by the U.K. wheat breeding team were representative of the diversity in the state. It also revealed that there were at least two novel Fusarium species, including one that appears to be undescribed, causing FHB symptoms in western Kentucky. The RFLP probes were also shown to be useful as genetic markers for segregation analysis and could be used in the future to monitor outcrossing in field populations.

In other work, we crossed two genetically and phenotypically similar strains of G. zeae and showed that this resulted in transgressive progeny that were significantly more aggressive and toxigenic than their parents. This was a surprising finding that showed that even when local strains appear to be similar in their pathogenicity, they have the potential to produce new and potentially more damaging strains by crossing.

Crossing in G. zeae is under control of MATing type genes. We deleted the complete MAT1 locus, and separately the two mating specificities, MAT1-1-1, and MAT1-2-1. Deletion of MAT1-1-1 and MAT1-2-1 genes had a significant negative effect on aggressiveness to wheat, and on mycotoxin production in planta and in vitro, while deletion of the complete MAT1 locus has no effect on disease development nor on mycotoxin production. This exciting result reveals a previously unsuspected role for MAT genes in mycotoxin production that will be further explored in future research.

2011 Impact

Mycotoxins are fungal metabolites that can adversely affect animal and human health. Mycotoxins can be produced in grain during storage or processing, but are most frequently associated with fungal infection that occurs before harvest. Generally, a basal level of mycotoxins is always present in US grain; however, in some years, environmental conditions lead to localized or widespread outbreaks of mycotoxin contamination.

Without an aggressive research program to prevent, treat, and contain outbreaks of mycotoxins in grain, US grain producers will suffer the consequences of reduced marketability of their products. The natural occurrence of mycotoxins in grain is an important security concern for the grain industry and end-users of grain; mycotoxins have been used as agents of terrorism, e.g. aflatoxin in Iraq. Stakeholders need cost-effective methods to predict, monitor, and minimize mycotoxin production in the field, and to detoxify mycotoxins and prevent further deterioration in contaminated grain.

The scientists involved in this multistate, multidisciplinary research proposal work individually on mycotoxin issues related to their respective disciplines and areas of expertise. The production of mycotoxins by mycotoxigenic fungi represents a basic aspect of agricultural science. Improving our understanding of how mycotoxin biosynthesis is regulated will not only lead to novel treatment strategies, but may also advance our understanding of fungal pathogenesis in general.