Crop Stress and Aflatoxin Contamination: Perspectives and Prevention Strategies

Abstract

The fungal metabolites called afl atoxins are potent naturally occurring carcinogens, produced primarily by Aspergillus fl avus and A. parasiticus . A. fl avus affects many agricultural crops such as maize, cotton, peanuts, and tree nuts. It can contaminate these crops with afl atoxins in the fi eld before harvest. It is a serious concern because of its toxic and carcinogenic properties and also due to the risk of contamination in food and feed on human health and livestock. It is not only a serious food safety issue, but it has signifi cant economic implications for the agricultural industry worldwide because of restrictions limiting the trade of contaminated crop. Host plant resistance is an effective, effi cient and dependable tool to protect crops from the preharvest infection and afl atoxin contamination processes. Host plant resistance to afl atoxin contamination is a complex trait, and dissecting this trait is an equally complex task. With the technological breakthrough in genomics and next-generation sequencing, our understanding on the Aspergillus biology is greatly enhanced. This chapter aggregates the rich afl atoxin literature and focuses on the factors that cause the stress execrably and increase the afl atoxin contamination of grains before and after harvest. Further discussed are potential future prevention technology and strategies that could be employed to guide future research, such as "next-generation" genetics.

Responses of Aspergillus flavus to Oxidative Stress Are Related to Fungal Development Regulator, Antioxidant Enzyme, and Secondary Metabolite Biosynthetic Gene Expression

“…The contamination of crops with aflatoxin, a carcinogenic secondary metabolite of the facultative plant parasite Aspergillus flavus (Guo et al, 1996), is a threat to human health, global food safety and security (Williams et al, 2010; Guo et al, 2012; Torres et al, 2014; Andrade and Caldas, 2015). Aflatoxin contamination of staple and dietary supplemental crops such as maize and peanut result in both losses in crop value in international trade due to restrictions on aflatoxin content (Matumba et al, 2015; Wu, 2015), and negative impacts in human and animal health (Williams et al, 2004, 2010; Kew, 2013).…”

“…Aflatoxin contamination of staple and dietary supplemental crops such as maize and peanut result in both losses in crop value in international trade due to restrictions on aflatoxin content (Matumba et al, 2015; Wu, 2015), and negative impacts in human and animal health (Williams et al, 2004, 2010; Kew, 2013). These concerns are the impetus for investigations into the biology of this organism and its interactions with host plants related to aflatoxin contamination (Diener et al, 1983, 1987; Amaike and Keller, 2011; Guo et al, 2012; Fountain et al, 2014). …”

Oxidative stress and carbon metabolism influence Aspergillus flavus transcriptome composition and secondary metabolite production

“…Over the last decade, several studies have elucidated the biosynthetic pathway for aflatoxin production and have begun to characterize upstream factors regulating its expression141516. Aflatoxin biosynthesis is carried out by a 25 gene-cluster that is highly conserved among toxigenic isolates of A. flavus 16.…”

Resistance to Aspergillus flavus in maize and peanut: Molecular biology, breeding, environmental stress, and future perspectives

“…It has been established that there exists a correlation between the drought tolerance of maize lines and their relative resistance to aflatoxin contamination under hot and dry conditions [5,26]. These conditions are also known to result in the accumulation of ROS in plant tissues, and, given that recent reports demonstrate that ROS can regulate aflatoxin production in Aspergillus spp., this provides a potential link between aflatoxin production and host-derived oxidative stress [19,25,41,53].…”

“…In addition, the link that exists between aflatoxin contamination and environmental stress, particularly drought stress, has also been a focal point of molecular research and applied breeding programs in recent years [5,[21][22][23][24][25]. Hence, the use of drought tolerant germplasm with aflatoxin resistance has gained momentum for selection in various genetic studies [21,26].…”