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In sub-Saharan Africa (SSA), diverse fungi belonging to Aspergillus section Flavi frequently contaminate staple crops with aflatoxins. Aflatoxins negatively impact health, income, trade, food security, and development sectors. Aspergillus flavus is the most common causal agent of contamination. However, certain A. flavus genotypes do not produce aflatoxins (i.e., are atoxigenic). An aflatoxin biocontrol technology employing atoxigenic genotypes to limit crop contamination was developed in the United States. The technology was adapted and improved for use in maize and groundnut in SSA under the trademark Aflasafe. Nigeria was the first African nation for which an aflatoxin biocontrol product was developed. The current study includes tests to assess biocontrol performance across Nigeria over the past decade. The presented data on efficacy spans years in which a relatively small number of maize and groundnut fields (8-51 per year) were treated through use on circa 36,000 ha in commercially-produced maize in 2018. During the testing phase (2009-2012), fields treated during one year were not treated in the other years while during commercial usage (2013-2019), many fields were treated in multiple years. This is the first report of a large-scale, long-term efficacy study of any biocontrol product developed to date for a field crop. Most (>95%) of 213,406 tons of maize grains harvested from treated fields contained <20 ppb total aflatoxins, and a significant proportion (>90%) contained <4 ppb total aflatoxins. Grains from treated plots had preponderantly >80% less aflatoxin content than untreated crops. The frequency of the biocontrol active ingredient atoxigenic genotypes in grains from treated fields was significantly higher than in grains from control fields. A higher proportion of grains from treated fields met various aflatoxin standards compared to grains from untreated fields. Results indicate that efficacy of the biocontrol product in limiting aflatoxin contamination is stable regardless of environment and cropping system. In summary, the biocontrol technology allows farmers across Nigeria to produce safer crops for consumption and increases potential for access to premium markets that require aflatoxin-compliant crops.
Across sub-Saharan Africa, chili peppers are fundamental ingredients of many traditional dishes. However, chili peppers may contain unsafe aflatoxin concentrations produced by Aspergillus section Flavi fungi. Aflatoxin levels were determined in chili peppers from three states in Nigeria. A total of 70 samples were collected from farmers’ stores and local markets. Over 25% of the samples contained unsafe aflatoxin concentrations. The chili peppers were associated with both aflatoxin producers and atoxigenic Aspergillus flavus genotypes. Efficacy of an atoxigenic biocontrol product, Aflasafe, registered in Nigeria for use on maize and groundnut, was tested for chili peppers grown in three states. Chili peppers treated with Aflasafe accumulated significantly less aflatoxins than nontreated chili peppers. The results suggest that Aflasafe is a valuable tool for the production of safe chili peppers. Use of Aflasafe in chili peppers could reduce human exposure to aflatoxins and increase chances to commercialize chili peppers in premium local and international markets. This is the first report of the efficacy of any atoxigenic biocontrol product for controlling aflatoxin in a spice crop.
Biological control is one of the recommended methods for aflatoxin mitigation. Biocontrol products must be developed, and their efficacy demonstrated before widespread use. Efficacy of two aflatoxin biocontrol products, Aflasafe GH01 and Aflasafe GH02, were evaluated in 800 maize and groundnut farmers' fields during 2015 and 2016 in the Ashanti, Brong Ahafo, Northern, Upper East, and Upper West regions of Ghana. Both products were developed after an extensive examination of fungi associated with maize and groundnut in Ghana. Each product contains as active ingredient fungi four
Aflatoxin contamination of crops is frequent in warm regions across the globe, including large areas in sub-Saharan Africa. Crop contamination with these dangerous toxins transcends health, food security, and trade sectors. It cuts across the value chain, affecting farmers, traders, markets, and finally consumers. Diverse fungi within Aspergillus section Flavi contaminate crops with aflatoxins. Within these Aspergillus communities, several genotypes are not capable of producing aflatoxins (atoxigenic). Carefully selected atoxigenic genotypes in biological control (biocontrol) formulations efficiently reduce aflatoxin contamination of crops when applied prior to flowering in the field. This safe and environmentally friendly, effective technology was pioneered in the US, where well over a million acres of susceptible crops are treated annually. The technology has been improved for use in sub-Saharan Africa, where efforts are under way to develop biocontrol products, under the trade name Aflasafe, for 11 African nations. The number of participating nations is expected to increase. In parallel, state of the art technology has been developed for large-scale inexpensive manufacture of Aflasafe products under the conditions present in many African nations. Results to date indicate that all Aflasafe products, registered and under experimental use, reduce aflatoxin concentrations in treated crops by >80% in comparison to untreated crops in both field and storage conditions. Benefits of aflatoxin biocontrol technologies are discussed along with potential challenges, including climate change, likely to be faced during the scaling-up of Aflasafe products. Lastly, we respond to several apprehensions expressed in the literature about the use of atoxigenic genotypes in biocontrol formulations. These responses relate to the following apprehensions: sorghum as carrier, distribution costs, aflatoxin-conscious markets, efficacy during drought, post-harvest benefits, risk of allergies and/or aspergillosis, influence of Aflasafe on other mycotoxins and on soil microenvironment, dynamics of Aspergillus genotypes, and recombination between atoxigenic and toxigenic genotypes in natural conditions.
Anthracnose, caused by Colletotrichum gloeosporioides, is one of the major constraints limiting water yam (Dioscorea alata) production in the tropics. In this region, yam anthracnose control is mostly achieved by the deployment of moderately resistant yam genotypes. Therefore, screening for new sources of anthracnose resistance is an important aspect of yam research in the tropics. The reliability and applicability of different yam anthracnose rating parameters has not been fully examined. Disease severity on detached leaves in the laboratory and leaf severity, lesion size, and spore production on whole plants in the greenhouse were used to screen an F1 yam population and correlate screening results with field evaluations. Anthracnose lesion size had the smallest predicted residual means but whole-plant severity and detached-leaf severity had the best variance homogeneity and relatively small predicted residual means. The concordance correlation coefficient (r c ) and κ statistic were used to determine the agreement between anthracnose rating parameters and field evaluations. Detached-leaf (r c = 0.95, κ = 0.81) and whole-plant (r c = 0.96, κ = 0.86) evaluations had high positive agreement with field evaluation but spore production (κ = 0.69) and lesion size (κ = 0.57) had moderate positive agreement. These results suggest that all the evaluated rating parameters can be used to successfully screen yam germplasm for anthracnose resistance but lesion size and spore production data may need to be transformed.
Aflatoxin (AF) contamination occurs throughout sub-Saharan Africa reducing trade opportunities and exposing populations to a potent carcinogen that causes liver cirrhosis, stunting, and reduced immune function.Use of atoxigenic strains of Aspergillus flavus to competitively exclude AF producers is an established tool for AF prevention in the US.Utilizing the same principles, highly effective biocontrol products were developed for several African nations.Each product uses 4 genetically distinct atoxigenic isolates of A. flavus as active ingredients.The isolates are endemic to target nations to ensure no introduction of exotics and adaptation to target agroecosystems.Adaptation to Africa began in Nigeria where the resulting product aflasafe™ was evaluated in farmer's fields for 5 seasons on over 500 fields.Treatments reduced AF by 82-95% in maize and peanut.Also in West Africa, products for Senegal (aflasafe SN01) and Burkina Faso (aflasafe BF01) were evaluated in farmer's fields for multiple seasons with reductions exceeding 75%.Aflasafe KE01, developed for Kenya in East Africa, where lethal aflatoxicoses has been repeatedly reported had excellent efficacy on farm for two seasons.In one area, untreated controls averaged >1,100 ppb and treated fields <75 ppb.The aflasafe biocontrol products have area-wide and long-term influences that offer real promise for relieving human populations in Africa of the health effects caused by chronic AF exposure. Role of plant elicitor peptides and phytoalexins in enhancing maize resistance to Aspergillus flavus infectionA. HUFFAKER (1), J. Sims (1), S. Christensen (1), E. A. Schmelz (1) (1) USDA-ARS CMAVE, Gainesville, FL, U.S.A. Phytopathology 104(Suppl.3):S3.139Maize responds to pests and pathogens with complex defense responses.To facilitate effective breeding for pest and pathogen resistance, we're elucidating cellular and molecular functions of regulatory and metabolic components of these maize defense responses.Our studies of regulatory components have focused on a family of peptide signals (ZmPeps) and their cognate receptors (ZmPEPRs) that regulate maize immunity.One of these, ZmPep1, triggers synthesis of plant defense phytohormones and induces expression of genes encoding pathogenesis-related proteins.ZmPep1 also promotes accumulation of the maize defense chemical HDMBOA-Glc.Treatment of maize plants with ZmPep1 prior to inoculation enhances resistance to fungal pathogens.A second peptide, ZmPep3, induces plant resistance responses against Lepidopteran herbivores associated with spread of mycotoxin-producing fungal pathogens.ZmPep3 stimulates expression of proteinase inhibitor genes and emission of volatiles that attract natural enemies of herbivorous pests.We've also discovered two families of fungalinduced terpenoid phytoalexins that accumulate at the plant pathogen interface, the kauralexins and zealexins.Several of these terpenoids have antimicrobial activity and we're examining their effects on aflatoxin production.We aim to provide understanding of molecular processes regulating maize defense and new strategies for enhancing resistance to pests, disease and mycotoxin accumulation. Genomic approaches to characterize the regulatory circuits ofAspergillus flavus controlling aflatoxin biosynthesis G. PAYNE (1), X. Shu (1), G. OBrian (1), B. Musungu (2), M. Geisler (2), A. M. Fakhoury (2) (
Aflatoxins pose significant food security and public health risks, decrease productivity and profitability of animal industries, and hamper trade. To minimize aflatoxin contamination in several crops, a biocontrol technology based on atoxigenic strains of Aspergillus flavus is commercially used in the United States and some African nations. Significant efforts are underway to popularize the use of biocontrol in Africa by various means including incentives. The purpose of this study was to develop quantitative pyrosequencing assays for rapid, simultaneous quantification of proportions of four A. flavus biocontrol genotypes within complex populations of A. flavus associated with maize crops in Nigeria to facilitate payment of farmer incentives for Aflasafe (a biocontrol product) use. Protocols were developed to confirm use of Aflasafe by small scale farmers in Nigeria. Fungal PCR amplicons were amplified directly from crude DNA preparations from ground corn. Proportions of A. flavus DNA composed of the four active ingredient A. flavus genotypes of Aflasafe were determined with pyrosequencing assays directed at single nucleotide polymorphisms (SNPs) in the amplicons. SNPs capable of distinguishing the active ingredients were identified with whole genome analyses. Two PCR amplifications combined with sequence by synthesis Pyrosequencing assays were required to quantify frequencies of the four Aflasafe active ingredients and, in so doing, confirm successful use of Aflasafe by participating farmers. Confirmation resulted in premium payments. The entire verification process could be completed in 3 to 4 days proving a savings over other monitoring methods in both time and costs and providing data in a time frame that could work with the commercial agriculture scheme. Quantitative pyrosequencing assays represent a reliable tool for rapid detection, quantification, and monitoring of multiple A. flavus genotypes within complex fungal communities, satisfying the requirements of the regulatory community and crop end-users that wish to determine which purchased crops were treated with the biocontrol product. Techniques developed in the current study can be modified for monitoring other crop-associated fungi.
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