Genetic Approaches to Eliminate Aflatoxin Contamination of Peanuts (UWI 49)
The goals of UWI 49 are divided into two distinct areas: 1) the University of Wisconsin component is working at the molecular level examining the genes controlling aflatoxin synthesis and the symbiotic relationship between the fungus and the peanut plant. Factors that influence the switch-on of genes for aflatoxin production and the extent which plant/fungal interactions can be controlled, which will build a clearer picture of the complex biosynthetic pathways involved in aflatoxin production, and the interaction that occurs between the fungus and the plant; 2) the University of Georgia component is addressing the developing country need for low cost methods for aflatoxin analysis. There are requirements both to screen out highly contaminated peanuts from the food chain. Existing commercial affinity column based semi-quantitative screening methods work extremely well, but are very expensive due to high prices of imported affinity columns.
In the Georgia-Botswana component of the project, a simple screening method for determining aflatoxin was developed, which used the VICAM column system and replaced the affinity column with a low-cost alumina-based column which can be made with low cost in-country materials. Using acetone extraction, bromination and fluorescence measurement a limit of detection of 5 ppb for total aflatoxins has been achieved and 300-400 samples can be analyzed per day. The approach needs validation. The use of a silica-based material (Protect-It) for use during storage of peanuts to reduce insect damage was studied. The sharp material acts by penetrating the insect shell of hard-bodied insects. The effectiveness of this material has been demonstrated in Botswana and more work is required to get more widespread acceptance. At the University of Wisconsin, work was at the molecular level examining the genes controlling aflatoxin synthesis and the symbiotic relationship between the fungus and the peanut plant. The project examined factors that influence the switch-on of genes for aflatoxin production and the extent which plant/fungi interactions can be controlled. Key genes in the peanut responsible for the release of oxylipins have been identified, and the role of fatty acids in these interactions, were being investigated. The results of the project were helping to build a clearer picture of the complex biosynthetic pathways involved in aflatoxin production, and the interaction that occur between fungus and plant. It was found that oxylipins (e.g., oxygenated fatty acids including the peanut seed defense compound 13 and 9 HPODE, Aspergillus endogenous compounds, psi factor) appear to act as ligands signaling fungal sporulation and, depending on which oxylipin is present, aflatoxin. The work could ultimately help direct construction of bioengineered plants resistant to fungal attack or not triggering aflatoxin biosynthesis, or the development of novel fungicides.
Dr. Nancy Keller, University of Wisconsin, Madison
Dr. David Wilson, University of Georgia
Dr. A. Siame, University of Botswana
South Africa Collaborator
Dr. Binesh Somai, University of Port Elizabeth