Abstract
At this time, no “magic bullet” for solving the aflatoxin contamination problem in maize and cottonseed has been identified, so several strategies must be utilized simultaneously to ensure a healthy crop, free of aflatoxins. The most widely explored strategy for the control of aflatoxin contamination is the development of preharvest host resistance. This is because A. flavus infects and produces aflatoxins in susceptible crops prior to harvest. In maize production, the host resistance strategy has gained prominence because of advances in the identification of natural resistance traits. However, native resistance in maize to aflatoxin contamination is polygenic and complex and, therefore, markers need to be identified to facilitate the transfer of resistance traits into agronomically viable genetic backgrounds while limiting the transfer of undesirable traits. Unlike maize, there are no known cotton varieties that demonstrate enhanced resistance to A. flavus infection and aflatoxin contamination. For this reason, transgenic approaches are being undertaken in cotton that utilize genes encoding antifungal/anti-aflatoxin factors from maize and other sources to counter fungal infection and toxin production. This review will present information on preharvest control strategies that utilize both breeding and native resistance identification approaches in maize as well as transgenic approaches in cotton.
Highlights
Aflatoxins, are highly toxic and carcinogenic compounds produced by the fungi, Aspergillus flavus and A. parasiticus during growth on crops such as maize, peanut, cottonseed, and tree nuts [1].A. flavus is most commonly associated with aflatoxin contamination of susceptible crops thoughA. parasiticus is often associated with contamination of peanut
Chromosome regions associated with resistance to A. flavus and inhibition of aflatoxin production in maize have been identified through Restriction Fragment Length Polymorphism (RFLP) analysis in three “resistant” lines (R001, LB31, and Tex6) in an Illinois breeding program, after mapping populations were developed using B73 and/or Mo17 elite inbreds as the “susceptible” parents [50,51]
The identification of natural resistance traits to aflatoxin accumulation in maize genotypes has provided an inroad to the development of a host resistance strategy in which genes encoding resistance associated proteins can be utilized as molecular markers for transfer of aflatoxin resistance traits into elite maize varieties
Summary
Aflatoxins, are highly toxic and carcinogenic compounds produced by the fungi, Aspergillus flavus and A. parasiticus during growth on crops such as maize, peanut, cottonseed, and tree nuts [1]. Developing countries in many regions of the world, such as Sub-Saharan Africa, cannot afford the costs associated with monitoring and mitigation of aflatoxin in food and feed crops. Several maize lines have been identified and developed with increased resistance to A. flavus infection and aflatoxin contamination and this has enabled the identification of natural resistance traits [10,11,12,13]. (2) identification of RAPs and their corresponding genes in maize kernels through comparative proteomics and genomics of resistant and susceptible maize inbreds; (3) development of practical technology for use by maize breeders based upon identification of RAP-associated proteins (and genes) as resistance markers to aid in marker-assisted maize breeding; and (4) production of genetically engineered cotton with resistance alleles of RAP genes from maize and genes from non-native sources to enhance resistance to aflatoxin contamination
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