|Bruns, Herbert - Arnold|
Submitted to: Journal of Toxicology Toxins Reviews
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/6/2009
Publication Date: 4/6/2009
Citation: Abbas, H.K., Wilkinson, J.R., Zablotowicz, R.M., Accinelli, C., Abel, C.A., Bruns, H.A., Weaver, M.A. 2009. Ecology of Aspergillus flavus, regulation of aflatoxin production and management strategies to reduce aflatoxin contamination of corn. Journal of Toxicology Toxins Reviews. 28(2-3):142-153. Interpretive Summary:
Technical Abstract: The contamination of corn (maize) by fungi and the accumulation of mycotoxins are a serious agricultural problem for human and animal health. One particular devastating group of mycotoxins, called aflatoxins, has been intensely studied since the 1960s. Studies of Aspergillus flavus, the agriculturally relevant producer of aflatoxins, have resulted in a well characterized biosynthetic pathway, as well as a basic understanding of the organism life cycle. Unfortunately, these efforts have not resulted in production practices that substantially reduce aflatoxin contamination. Similarly the use of agrochemicals (e.g., fungicides) results in very limited reduction of the fungus or the toxin. Thus, cultural management (fertility and irrigation) coupled with aggressive insect management provide the current state of the art for integrated aflatoxin management. The development of resistant hybrids appears to be a very promising technology, but commercial hybrids are still not available. Thus, biocontrol appear to be the most promising available avenue of reducing aflatoxin accumulation. Biocontrol utilizes non-toxigenic strains of Aspergillus to reduce the incidence of toxin-producing isolates through competition. To maximize the effectiveness of biocontrol, a thorough knowledge of the environmental factors influencing colonization and growth of Aspergillius is needed. A. flavus not only colonizes tissue of plants, but saprophytically grows in the soil on plant residues. These residues serve as a reservoir for the fungus, allowing it to overwinter and under favorable conditions to resume growth and release new conidia. The conidia can be transmitted by air or insects to serve as new inoculum on host plants or debris in the field. This complex ecology of Aspergilli has been studied, but our understanding lags behind what is known about biosynthesis of the toxin itself. Our limited understanding of Aspergilli soil ecology is in part due to limitations in evaluating Aspergilli, aflatoxin, and the biosynthetic genes in the varying aspects of the environment. Current methods for assessing Aspergillus and aflatoxin accumulation rely heavily on cultural and analytical methods that are low throughput and technically challenging. Thus to understand Aspergillus ecology and environmental effects in contamination to maximize biocontrol efforts, it is necessary to understand current treatment effects and to develop methodologies capable of assessing the fungal populations present. To that end we discuss in this manuscript the current knowledge of A. flavus ecology, the application of selected molecular techniques to field assessments, and crop practices used to reduce aflatoxin contamination, focusing on chemical treatments (fungicides and herbicides), insect management, and crop management.