Increasing knowledge of the deleterious health and economic impacts of aflatoxin in crop commodities has stimulated global interest in aflatoxin mitigation. Current evidence of the incidence of Aspergillus flavus isolates belonging to vegetative compatibility groups (VCGs) lacking the ability to produce aflatoxins (i.e., atoxigenic) in Ghana may lead to the development of an aflatoxin biocontrol strategy to mitigate crop aflatoxin content. In this study, 12 genetically diverse atoxigenic African A. flavus VCGs (AAVs) were identified from fungal communities associated with maize and groundnut grown in Ghana. Representative isolates of the 12 AAVs were assessed for their ability to inhibit aflatoxin contamination by an aflatoxin-producing isolate in laboratory assays. Then, the 12 isolates were evaluated for their potential as biocontrol agents for aflatoxin mitigation when included in three experimental products (each containing four atoxigenic isolates). The three experimental products were evaluated in 50 maize and 50 groundnut farmers’ fields across three agroecological zones (AEZs) in Ghana during the 2014 cropping season. In laboratory assays, the atoxigenic isolates reduced aflatoxin biosynthesis by 87–98% compared to grains inoculated with the aflatoxin-producing isolate alone. In field trials, the applied isolates moved to the crops and had higher (P < 0.05) frequencies than other A. flavus genotypes. In addition, although at lower frequencies, most atoxigenic genotypes were repeatedly found in untreated crops. Aflatoxin levels in treated crops were lower by 70–100% in groundnut and by 50–100% in maize (P < 0.05) than in untreated crops. Results from the current study indicate that combined use of appropriate, well-adapted isolates of atoxigenic AAVs as active ingredients of biocontrol products effectively displace aflatoxin producers and in so doing limit aflatoxin contamination. A member each of eight atoxigenic AAVs with superior competitive potential and wide adaptation across AEZs were selected for further field efficacy trials in Ghana. A major criterion for selection was the atoxigenic isolate’s ability to colonize soils and grains after release in crop field soils. Use of isolates belonging to atoxigenic AAVs in biocontrol management strategies has the potential to improve food safety, productivity, and income opportunities for smallholder farmers in Ghana.

Aflatoxin contamination in maize and groundnut is perennial in Ghana with substantial health and economic burden on the population. The present study examined for the first time the prevalence of aflatoxin contamination in maize and groundnut in major producing regions across three agroecological zones (AEZs) in Ghana. Furthermore, the distribution and aflatoxin-producing potential of Aspergillus species associated with both crops were studied. Out of 509 samples (326 of maize and 183 of groundnut), 35% had detectable levels of aflatoxins. Over 15% of maize and 11% of groundnut samples exceeded the aflatoxin threshold limits set by the Ghana Standards Authority of 15 and 20 ppb, respectively. Mycoflora analyses revealed various species and morphotypes within the Aspergillus section Flavi. A total of 5,083 isolates were recovered from both crops. The L morphotype of Aspergillus flavus dominated communities with 93.3% of the population, followed by Aspergillus spp. with S morphotype (6%), A. tamarii (0.4%), and A. parasiticus (0.3%). Within the L morphotype, the proportion of toxigenic members was significantly (P < 0.05) higher than that of atoxigenic members across AEZs. Observed and potential aflatoxin concentrations indicate that on-field aflatoxin management strategies need to be implemented throughout Ghana. The recovered atoxigenic L morphotype fungi are genetic resources that can be employed as biocontrol agents to limit aflatoxin contamination of maize and groundnut in Ghana. [Formula: see text] Copyright © 2018 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .

Highlights Efficacy of 2 aflatoxin biocontrol products reported across crops, years and zones. Aflatoxin reduced by 99% in 800 maize and groundnut farmers’ fields in Ghana. Results are the most consistent and highest aflatoxin reductions reported to date. Displacement of toxigenic fungi by the active ingredients caused the reductions. Having both products offers greater versatility to modulate Aspergillus communities.

In the tropics and subtropics, maize and other crops are frequently contaminated with aflatoxins by Aspergillus flavus. Treatment of crops with atoxigenic isolates of A. flavus formulated into biocontrol products can significantly reduce aflatoxin contamination. Treated crops contain up to 100% less aflatoxins compared to untreated crops. However, there is the notion that protecting crops from aflatoxin contamination may result in increased accumulation of other toxins, particularly fumonisins produced by a few Fusarium species. The objective of this study was to determine if treatment of maize with aflatoxin biocontrol products increased fumonisin concentration and fumonisin-producing fungi in grains. Over 200 maize samples from fields treated with atoxigenic biocontrol products in Nigeria and Ghana were examined for fumonisin content and contrasted with maize from untreated fields. Apart from low aflatoxin levels, most treated maize also harbored fumonisin levels considered safe by the European Union (< 1 part per million). Most untreated maize also harbored equally low fumonisin levels but contained higher aflatoxin levels. In addition, during one year, we detected considerably less Fusarium spp. densities in treated maize than in untreated maize. Our results do not support the hypothesis that treating crops with atoxigenic isolates of A. flavus used in biocontrol formulations results in higher grain fumonisin levels.

Aflatoxin contamination in foods is a vital health challenge for low and middle-income countries in subtropical regions. Maize (Zea mays L.), a staple food most widely grown in Africa including Ghana, and extensively consumed as much as three times per day, is a source of aflatoxin contamination owing to its susceptibility to fungal infection. Aflatoxin levels were checked against international (European Commission, EC) and local (Ghana Standards Authority, GSA) standards, and health risks associated with maize sampled from the Volta Region (Hohoe, Ho, Battor Dugame, and Keta) of Ghana were determined. Total aflatoxins (totalAFs) and the constituent aflatoxins (AFB1, AFB2, AFG1, and AFG2) were measured with High-Performance Liquid Chromatography (HPLC) with a Fluorescence Detector (FLD). Intake and Risk assessments were also conducted using deterministic models prescribed by the Joint FAO/WHO Expert Committee on Additives (JECFA). The degree of occurrence of aflatoxins was observed to be in decreasing order of AFG2 < AFG1 < AFB2 < AFB1 and were within the ranges of 0.78 ± 0.04 $$-$$ - 234.73 ± 3.8 µg/kg, 0.47 ± 0.03 $$-$$ - 21.6 ± 0.33 µg/kg, 1.01 ± 0.05 $$-$$ - 13.75 ± 1.2 µg/kg and 0.66 ± 0.06 $$-$$ - 5.51 ± 0.26 µg/kg respectively. Out of the 100 samples analyzed for total aflatoxins (totalAFs), 68 (68%) exceeded the limits of EC and were of range 4.98 ± 0.6 $$-$$ - 445.01 ± 8.9 µg/kg whereas 58 (58%) and ranged between 12.12 ± 1.4 $$-$$ - 445.01 ± 8.9 µg/kg exceeded GSA limits. Intake and risk assessments of total aflatoxins (totalAFs) for infants, toddlers, children, adolescents, and adults in the Volta Region were; 0.037–1.14 µg/kg bw/day, 0.35–10.81, and 1.47 -45.14 cases/10,000 person/yr respectively for Estimated Daily Intake (EDI), Margin of Exposure (MOE), and Cancer Risks. It was inferred that the consumption of maize posed potential adverse health effects on all age categories studied because all calculated MOE values were less than 10,000.