Article

Development of Biocontrol Technology to Manage Aflatoxin Contamination in Peanuts

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Abstract

Aflatoxin contamination of peanuts results from invasion and growth of the fungi, Aspergillus flavus and A. parasiticus. Peanut pods develop in the soil where they are in contact with propagules of these ubiquitous fungi. When peanuts are subjected to drought conditions as pods are maturing, they become susceptible to contamination. A method of biological control of aflatoxin contamination was developed in which a competitive, nontoxigenic strain of A. flavus is applied to the soil to competitively exclude the toxigenic strains in the invasion of peanuts. The biocontrol product is comprised of conidia of the nontoxigenic strain coated onto the surface of hulled barley, which is applied to peanut fields during the middle of the growing season. After uptake of moisture the conidia germinate, grow, and sporulate, yielding a dominant population of the nontoxigenic strain in the soil. Several plot and field studies showed that aflatoxin in farmers' stock peanuts was reduced by 80 to 90% with this technique. The patented technology was licensed by a company that markets the biocontrol product under the trade name, afla-guard®. In 2004, the U. S. Environmental Protection Agency issued a Section 3 registration for use of afla-guard® to control aflatoxin contamination in peanuts. Analyses of peanuts from the first commercial use of afla-guard® in various locations in Georgia and Alabama showed aflatoxin reductions averaging 85% in farmers' stock peanuts and as high as 98% in shelled stock.

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... For example, a direct spray application of atoxigenic A. flavus strain is better than soil inoculation in controlling maize aflatoxin contamination, and that a water-dispersible granule is a viable delivery system for maintaining viability and efficacy of the biological control agent K49 (Lyn et al., 2009). In the case of peanut, it is recommended that the inoculum be applied at 22.5 kg ha −1 in the field at between 60 and 80 days after planting when the foliage canopy is well developed and at a time when enough soil moisture is available (Dorner, 2009a). ...
... Afla-Guard ® is now commercially used to prevent aflatoxin contamination in peanut in the USA. The Afla-Guard ® has so far been applied approximately in 2000 ha in the states of Alabama and Georgia to test its efficacy in controlling the aflatoxin in peanut, which resulted in mean reduction in aflatoxin concentration by 85% in the treated peanuts (Dorner, 2009a). Similar package has also been developed, and is in use to control aflatoxin contamination in peanut in Australia (Pit and Hocking, 2006). ...
... Taken together, it is encouraging to be optimistic that the goal of highyielding wheat transgenic lines would be achievable in near future if adequate transformation and screening protocols are implemented. Bhatnagar-Mathur et al. (2007, 2009a introduced P5CSF129A in chickpea and DREB1A in peanut. Both are driven by the stress-inducible promoter rd29A. ...
Article
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... This review addresses available technologies for mitigating aflatoxin contamination, clearly stating their advantages and disadvantages, discussing barriers to their adoption, and identifying gaps still in need of research. Newer technologies are gaining momentum, such as biological control using nontoxigenic strains of Aspergillus flavus (Bandyopadhyay and Cotty 2013;Bandyopadhyay et al. 2016;Cotty 1990;Dorner 2009;Dorner et al. 2003;Fravel 2005). The biocontrol approach is being presented to farmers in Africa as an anchor technology that other aflatoxin mitigation efforts should complement (Bandyopadhyay et al. 2016). ...
... Other published results from biocontrol studies indicate that biocontrol significantly reduces aflatoxin contamination (Dorner 2009). However, it is also apparent from these published results that aflatoxin reduction using biocontrol may leave farmers with a harvest that is still contaminated at a level above the regulatory requirements. ...
... However, it is also apparent from these published results that aflatoxin reduction using biocontrol may leave farmers with a harvest that is still contaminated at a level above the regulatory requirements. Dorner (2009), one of the scientists behind the biocontrol product Afla-Guard (nontoxigenic strain of A. flavus NRRL 21882), published summarized results from a study on the development of the Afla-Guard biocontrol. The results presented reveal that in areas where biocontrol was tested that had little to no drought, aflatoxin was very low in both the control and the treated peanuts. ...
Article
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Peanut (Arachis hypogaea L.) is an important crop in Malawi and Zambia. The crop is valued for soil improvement in cereal-based cropping systems, for improving the livelihoods of farming households who consume it and also sell it for cash, and for earning foreign exchange when exported. Research and development efforts have resulted in an increase in both area under peanut production and productivity. However, a key challenge that still needs to be solved in these countries is how to produce peanuts with acceptable levels of aflatoxin contamination. Data continues to show that aflatoxin continues to be a problem in both formal and informal trade. As a result, unlike 30 years ago, most of the peanut trade has now shifted to domestic and regional markets that do not restrict the sale of aflatoxin-contaminated peanuts. Impacts of aflatoxin contamination on health and also on the full cost burden of control are not well documented. Technologies are available for mitigating against aflatoxin contamination. The advantages, disadvantages, and gaps associated with these technologies are discussed. A lot of money and effort continues to be invested in Malawi and Zambia into mitigating against aflatoxin contamination, but evidence of long-term success is limited. Based on past and current initiatives, the prospects of eliminating aflatoxin in the near future at the household level and in trade are not promising.
... This indicates that both aflatoxin accumulation and compositions of communities of aflatoxin-producing fungi were influenced by the use of Aflasafe SN01. Although effectiveness of biological control in reducing aflatoxin in groundnut has been reported in the United States (Dorner 2009) and Argentina (Alaniz Zanon et al. 2013), this is the first report of the efficacy of biocontrol for aflatoxin management in groundnut in Africa. Reduced variance in aflatoxin content is an advantage of atoxigenic genotype-based biocontrol not previously reported. ...
... Substantial aflatoxin reductions in crops occurred in treated fields both at harvest (range = 58.3 to 100%) and throughout storage (range = 76.2 to 95.4%). Similar levels of reductions were reported in the United States and Argentina (Alaniz Zanon et al. 2013;Dorner 2009). Most crops from treated fields in most years had aflatoxin content meeting quality standards for sale in premium markets. ...
... Although it is true that atoxigenic isolates would not sporulate on the carrier when there are long periods of drought, the fungi sporulate as soon as moist conditions return. Dorner (2009) demonstrated that biocontrol was particularly effective when aflatoxin conducive situation was promoted by drought stress. Although we did not collect water stress data in the trial sites, the groundnut basin, where the trials were conducted, is known to be drought prone (Clavel et al. 2005;Tschakert and Tappan 2004). ...
Article
Full-text available
Aflatoxin contamination of groundnut and maize infected by Aspergillus section Flavi fungi is common throughout Senegal. The use of biocontrol products containing atoxigenic Aspergillus flavus strains to reduce crop aflatoxin content has been successful in several regions, but no such products are available in Senegal. The biocontrol product Aflasafe SN01 was developed for use in Senegal. The four active ingredients of Aflasafe SN01 are atoxigenic A. flavus genotypes native to Senegal and distinct from active ingredients used in other biocontrol products. Efficacy tests on groundnut and maize in farmers’ fields were carried out in Senegal during the course of 5 years. Active ingredients were monitored with vegetative compatibility analyses. Significant (P < 0.05) displacement of aflatoxin producers occurred in all years, districts, and crops. In addition, crops from Aflasafe SN01-treated fields contained significantly (P < 0.05) fewer aflatoxins both at harvest and after storage. Most crops from treated fields contained aflatoxin concentrations permissible in both local and international markets. Results suggest that Aflasafe SN01 is an effective tool for aflatoxin mitigation in groundnut and maize. Large-scale use of Aflasafe SN01 should provide health, trade, and economic benefits for Senegal. [Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .
... The biocontrol product AF36 is now used in several states across the US, which makes it the most widely used aflatoxin biocontrol product in the world. A second biocontrol product, Afla-guard ® , containing a different atoxigenic A. flavus isolate (NRRL21882) as an active ingredient, was registered with USEPA for use in maize and groundnut in the US [58]. The product Afla-guard ® is commercialized by Syngenta Crop Protection, Inc. (Greensboro, NC, US) and has been used in experimental groundnut fields in Turkey [59]. ...
... Field testing allows evaluating aflatoxin reduction abilities of candidate fungi under field conditions [50][51][52]54,58]. When selecting atoxigenic fungi for multi-isolate products, field evaluations are done by applying atoxigenic isolates individually (typically 12 isolates are tested) and then, as part of a candidate multi-isolate products [26,47,50]. ...
... Although this methodology was effective to deliver the biocontrol agent to the crop, it was expensive and slow to produce. Therefore, formulations using roasted or dehulled grains (to avoid germination) coated with a spore suspension of the biocontrol isolate(s) were developed [26,58,95]. Coated formulations lower the costs and increase the rate of product manufacture, making it more affordable for farmers. ...
Article
Full-text available
Aflatoxin contamination of important food and feed crops occurs frequently in warm tropical and subtropical regions. The contamination is caused mainly by Aspergillus flavus and A. parasiticus. Aflatoxin contamination negatively affects health and trade sectors and causes economic losses to agricultural industries. Many pre-and post-harvest technologies can limit aflatoxin contamination but may not always reduce aflatoxin concentrations below tolerance thresholds. However, the use of atoxigenic (non-toxin producing) isolates of A. flavus to competitively displace aflatoxin producers is a practical strategy that effectively limits aflatoxin contamination in crops from field to plate. Biocontrol products formulated with atoxigenic isolates as active ingredients have been registered for use in the US, several African nations, and one such product is in final stages of registration in Italy. Many other nations are seeking to develop biocontrol products to protect their crops. In this review article we present an overview of the biocontrol technology, explain the basis to select atoxigenic isolates as active ingredients, describe how formulations are developed and tested, and describe how a biocontrol product is used commercially. Future perspectives on formulations of aflatoxin biocontrol products, along with other important topics related to the aflatoxin biocontrol technology are also discussed.
... The first application of this technology was done by the US Agricultural Research Service of the Department of Agriculture (USDA-ARS) in 2003 on cotton using atoxigenic A. flavus AF36 strain, which was then registered with the US Environmental Protection Agency (USEPA) [229]. The following year, the same entity patented this technology as a biocontrol product that was licenced by a company under the trade name of afla-guard ® [230]. As this technology proved to be an efficient biocontrol means to mitigate aflatoxin contamination in various crops, studies have been conducted in different countries and regions of the world to screen for proficient strains and well adapted to specific soils and AEZs. ...
... This strain is now marketed as a biopesticide under the trade name of AF-X1™. Other successful field trials of different scales have been reported in different countries emphasising the anticipated success of this promising technology in the protection of crops against aflatoxin contamination for field to consumption [230,231,233,234]. ...
Article
Full-text available
This review aims to update the main aspects of aflatoxin production, occurrence and incidence in selected countries, and associated aflatoxicosis outbreaks. Means to reduce aflatoxin incidence in crops were also presented, with an emphasis on the environmentally-friendly technology using atoxigenic strains of Aspergillus flavus. Aflatoxins are unavoidable widespread natural contaminants of foods and feeds with serious impacts on health, agricultural and livestock productivity, and food safety. They are secondary metabolites produced by Aspergillus species distributed on three main sections of the genus (section Flavi, section Ochraceorosei, and section Nidulantes). Poor economic status of a country exacerbates the risk and the extent of crop contamination due to faulty storage conditions that are usually suitable for mold growth and mycotoxin production: temperature of 22 to 29 °C and water activity of 0.90 to 0.99. This situation paralleled the prevalence of high liver cancer and the occasional acute aflatoxicosis episodes that have been associated with these regions. Risk assessment studies revealed that Southeast Asian (SEA) and Sub-Saharan African (SSA) countries remain at high risk and that, apart from the regulatory standards revision to be more restrictive, other actions to prevent or decontaminate crops are to be taken for adequate public health protection. Indeed, a review of publications on the incidence of aflatoxins in selected foods and feeds from countries whose crops are classically known for their highest contamination with aflatoxins, reveals that despite the intensive efforts made to reduce such an incidence, there has been no clear tendency, with the possible exception of South Africa, towards sustained improvements. Nonetheless, a global risk assessment of the new situation regarding crop contamination with aflatoxins by international organizations with the required expertise is suggested to appraise where we stand presently.
... Another potential means for aflatoxin control is the biocontrol of fungal growth in the field. Numerous organisms have been tested for biological control of aflatoxin contamination including bacteria, yeasts, and non-toxigenic (atoxigenic) strains of the causal organisms (Yin et al., 2008) of which only atoxigenic strains have reached the commercial stage (Dorner, 2009). Biological control of aflatoxin production in crops in the US has been approved by the Environmental Protection Agency and two commercial products based on atoxigenic Aspergillus flavus strains are being used (afla-guard® and AF36®), for the prevention of aflatoxin in peanuts, corn and cotton seed (Dorner, 2009). ...
... Numerous organisms have been tested for biological control of aflatoxin contamination including bacteria, yeasts, and non-toxigenic (atoxigenic) strains of the causal organisms (Yin et al., 2008) of which only atoxigenic strains have reached the commercial stage (Dorner, 2009). Biological control of aflatoxin production in crops in the US has been approved by the Environmental Protection Agency and two commercial products based on atoxigenic Aspergillus flavus strains are being used (afla-guard® and AF36®), for the prevention of aflatoxin in peanuts, corn and cotton seed (Dorner, 2009). In Africa, atoxigenic strains of A. flavus have been identified to competitively exclude toxigenic fungi in the maize and peanut fields. ...
Article
Full-text available
Mycotoxins are secondary fungal metabolites that contaminate agricultural commodities and can cause sickness or death in humans and animals. Risk of mycotoxin contamination of food and feed in Africa is increased due to environmental, agronomic and socio-economic factors. Environmental conditions especially high humidity and temperature favour fungal proliferation. Farming practices in Africa sustain fungal and toxin contamination of food and feed. The socio-economic and food security status of the majority of inhabitants of sub-Saharan Africa leaves them little option in choosing good quality products. Several technologies have been tested in Africa to reduce mycotoxin risk. Field management practices that increase yields may also prevent aflatoxin. They include use of resistant varieties, timely planting, fertilizer application, weed control, insect control and avoiding drought and nutritional stress. Other options to control the toxin causing fungi A. flavus contamination in the field are use of atoxigenic fungi to competitively displace toxigenic fungi, and timely harvest. Post-harvest interventions that reduce mycotoxins are rapid and proper drying, sorting, cleaning, drying, smoking, post harvest insect control, and the use of botanicals or synthetic pesticides as storage protectant. Another approach is to reduce the frequent consumption of 'high risk' foods (especially maize and groundnut) by consuming a more varied diet, and diversifying into less risky staples like sorghum and millet. Chemo-preventive measures that can reduce mycotoxin effect include daily consumption of chlorophyllin or oltipraz and by incorporating hydrated sodium calcium alumino-silicates into the diet. Detoxification of aflatoxins is often achieved physically (sorting, physical segregation, flotation etc.), chemically (with calcium hydroxide, ammonia) and microbiologically by incorporating pro-biotics or lactic acid bacteria into the diet. There is need for efficient monitoring and surveillance with cost-effective sampling and analytical methods. Sustaining public education and awareness can help to reduce aflatoxin contamination.
... There are four major aflatoxins (B1, B2, G1 and G2) and two additional metabolic products (M1 and M2) that are contaminants of food and feeds produced by toxigenic strains of the fungi, A. flavus and A. parasiticus (Horn & Dorner 2009). Aflatoxins are well recognized as potent toxic carcinogenic, mutagenic, immunosuppressive and teratogenic agents and are common contaminants in foods, particularly in the staple diets of many developing countries, posing a serious health risk to consumers (Dorner 2009). The quantity of aflatoxin in food and feed is therefore closely monitored and regulated in most countries. ...
... Many strategies including biological control, chemical control and development of resistant cultivars have been investigated to manage aflatoxin producing fungi in crops. Among them, biological control appears to be the most promising, safe, economic and environmentally friendly approach for control of these fungi during pre-harvest where aflatoxin contamination begins and carries through the value chain to storage and consumption (Dorner 2009 1014.89 μg kg -1 in the control treatment. ...
Article
Pre-harvest infection of groundnuts (Arachis hypogaea) by Aspergillus flavus creates a major food safety problem worldwide. Many strains of Aspergillus flavus and A. parasiticus produce aflatoxins, which are potent carcinogenic substances. A kaolin-based formulation of a biocontrol agent containing conidia of Trichoderma harzianum strain kd isolate was evaluated for its ability to control A. flavus in both in vitro and in vivo experiments. Plants were water stressed three weeks before harvest to condition infection by A. flavus. Aflatoxin content in groundnut seeds determined using a MaxiSignal®Aflatoxin B1 ELISA test kit showed that seeds of plants treated with T. harzianum strain kd and A. flavus developed 56.9% less aflatoxin B1 than the seeds of the A. flavus inoculated control plants. In vitro bioassay using dual culture technique showed a 73.3% inhibition of mycelial growth of A. flavus by T. harzianum strain kd, with clear evidence of antibiosis. Interaction studies under environmental scanning electron microscope (ESEM) also revealed mycoparasitism by T. harzianum strain kd, associated with mycelial coiling around hyphae of A. flavus. Overall, the results show that the T. harzianum strain kd isolate used in this study has a great potential for use as a biocontrol agent for pre-harvest aflatoxin contamination in groundnuts under drought stress conditions.
... Additionally, biological controls to minimize A. flavus and A. parasiticus have been introduced (Dorner et al., 2003). Application of the strains of A. flavus and A. parasiticus that are nonaflatoxigenic, such as the A. flavus NRRL 21882 strain, has been successful in reducing aflatoxin contamination in peanut (Dorner, 2009). For example, Dorner (2009) reported reductions in aflatoxin concentrations following application of Afla-Guard® compared to non-treated peanut ( Table 2). ...
... Application of the strains of A. flavus and A. parasiticus that are nonaflatoxigenic, such as the A. flavus NRRL 21882 strain, has been successful in reducing aflatoxin contamination in peanut (Dorner, 2009). For example, Dorner (2009) reported reductions in aflatoxin concentrations following application of Afla-Guard® compared to non-treated peanut ( Table 2). Use of the non-aflatoxigenic biological control is being evaluated worldwide in the public and private sectors. ...
... High levels of applied atoxigenic genotypes in the treated crops are associated with low levels of aflatoxins (Agbetiameh et al., 2020;Doster et al., 2014;Mehl et al., 2012;Shenge et al., 2019). In general, treated and untreated fields and crops contain the same fungal densities (Agbetiameh et al., 2020;Atehnkeng et al., 2014;Bock et al., 2004;Dorner, 2009;Doster et al., 2014;Senghor et al., 2020). ...
... Palacios, CIMMYT, personal communication). Another aflatoxin biocontrol product used in the United States is Afla-guard®, which is registered with the US EPA and manufactured by Syngenta® for use in maize and groundnut (Dorner, 2009). ...
Chapter
Full-text available
Aflatoxins pose a significant public health risk, decrease productivity and profitability and hamper trade. To minimize aflatoxin contamination a biocontrol technology based on atoxigenic strains of Aspergillus flavus that do not produce aflatoxin is used widely in the United States. The technology, with the generic name Aflasafe, has been improved and adapted for use in Africa. Aflasafe products have been developed or are currently being developed in 20 African countries. Aflatoxin biocontrol is being scaled up for use in several African countries through a mix of public, private, and public-private interventions. Farmers in several countries have commercially treated nearly 400,000 ha of maize and groundnut achieving >90% reduction in aflatoxin contamination. This chapter summarizes the biology of aflatoxin-producing fungi and various factors affecting their occurence, including climate change. Various management practices for aflatoxin mitigation are then discussed. These include biological control, which is increasingly being adopted by farmers in several countries. We discuss biocontrol product development and commercialization in various African countries. Subsequently, we highlight some barriers to adoption and other challenges.
... The first application of this technology was done by the US Agricultural Research Service of the Department of Agriculture (USDA-ARS) in 2003 on cotton using atoxigenic A. flavus AF36 strain, which was then registered with the US Environmental Protection Agency (USEPA) [229]. The following year, the same entity patented this technology as a biocontrol product that was licenced by a company under the trade name of afla-guard ® [230]. As this technology proved to be an efficient biocontrol means to mitigate aflatoxin contamination in various crops, studies have been conducted in different countries and regions of the world to screen for proficient strains and well adapted to specific soils and AEZs. ...
... This strain is now marketed as a biopesticide under the trade name of AF-X1™. Other successful field trials of different scales have been reported in different countries emphasising the anticipated success of this promising technology in the protection of crops against aflatoxin contamination for field to consumption [230,231,233,234]. ...
Preprint
Full-text available
Aflatoxins continue to raise health concerns as unavoidable and widespread natural contaminants of foods and feeds with serious impact on health, agricultural and livestock productivity, and food safety. They are secondary metabolites produced by Aspergillus species distributed on three main sections of the genus (section Flavi, section Ochraceorosei, and section Nidulantes). Aflatoxin-producing species, mainly A. flavus and A. parasiticus thrive under hot and humid conditions in the field or during storage, which are met in tropical and sub-tropical regions. Poor economic status of a country exacerbates the risk and the extent of crop contamination due to faulty storage conditions that are usually suitable for mold growth and mycotoxin production; temperature of 22 to 29°C and water activity of 0.90 to 0.99. This situation paralleled the prevalence of high liver cancer and the occasional acute aflatoxicosis episodes that have been associated with these regions. Few of the presently known aflatoxins (>18) have been sufficiently studied for their incidence, health-risk, and mechanisms of toxicity to allow effective intervention and control means that would significantly and sustainably reduce their incidence and adverse effects on health and economy. Among these, aflatoxin B1 (AFB1) has by far been the most studied; and yet, many aspects of the range and mechanisms of the diseases it causes remain to be elucidated. Its mutagenicity, tumorigenicity, and carcinogenicity, which are the best known still suffer from many limitations regarding the relative contribution of the oxidative stress and the reactive epoxide derivative (Aflatoxin-exo 8,9-epoxide) in the induction of the diseases, as well as its metabolic and synthesis pathways. Additionally, despite the well-established additive effects for carcinogenicity between AFB1 and other risk factors, e.g., hepatitis viruses B and C, and the algal hepatotoxic microcystins, the mechanisms of this synergy remain unclear. A review of publications on the incidence and concentrations of aflatoxins in selected foods and feeds from countries whose crops are classically known for their highest contamination with aflatoxins, reveals that despite the intensive efforts made to reduce such an incidence, there has been no clear tendency, with the possible exception of South Africa, towards sustained improvements. The levels and incidence are essentially influenced by the rainfall and temperature during the cultivation year or two successive years with alternating dry and wet seasons. This review aimed to update the main aspects of aflatoxin production, occurrence and incidence in selected countries, and associated adverse health effects. In addition to AFB1 which was the main focus of the review, other aflatoxins were addressed whenever relevant data were available.
... The first application of this technology was done by the US Agricultural Research Service of the Department of Agriculture (USDA-ARS) in 2003 on cotton using atoxigenic A. flavus AF36 strain, which was then registered with the US Environmental Protection Agency (USEPA) [229]. The following year, the same entity patented this technology as a biocontrol product that was licenced by a company under the trade name of afla-guard ® [230]. As this technology proved to be an efficient biocontrol means to mitigate aflatoxin contamination in various crops, studies have been conducted in different countries and regions of the world to screen for proficient strains and well adapted to specific soils and AEZs. ...
... This strain is now marketed as a biopesticide under the trade name of AF-X1™. Other successful field trials of different scales have been reported in different countries emphasising the anticipated success of this promising technology in the protection of crops against aflatoxin contamination for field to consumption [230,231,233,234]. ...
Preprint
Full-text available
This review aimed to update the main aspects of aflatoxin production, occurrence and incidence in selected countries, and associated aflatoxicosis outbreaks. Means to reduce aflatoxin incidence in crops were also presented with an emphasis on the environment-friendly technology using atoxigenic strains of Aspergillus flavus. Aflatoxins are unavoidable widespread natural contaminants of foods and feeds with serious impact on health, agricultural and livestock productivity, and food safety. They are secondary metabolites produced by Aspergillus species distributed on three main sections of the genus (section Flavi, section Ochraceorosei, and section Nidulantes). Poor economic status of a country exacerbates the risk and the extent of crop contamination due to faulty storage conditions that are usually suitable for mold growth and mycotoxin production: temperature of 22 to 29°C and water activity of 0.90 to 0.99. This situation paralleled the prevalence of high liver cancer and the occasional acute aflatoxicosis episodes that have been associated with these regions. Risk assessment studies revealed that Southeast Asian and Sub-Saharan African countries remain at high risk and that, apart from the regulatory standards revision to be more restrictive, other actions to prevent or decontaminate crops are to be taken for adequate public health protection. Indeed, a review of publications on the incidence of aflatoxins in selected foods and feeds from countries whose crops are classically known for their highest contamination with aflatoxins, reveals that despite the intensive efforts made to reduce such an incidence, there has been no clear tendency, with the possible exception of South Africa, towards sustained improvements. Nonetheless, a global risk assessment of the new situation regarding crop contamination with aflatoxins by international organizations with the required expertise is suggested to appraise where we stand presently.
... Several strains of A. flavus and A. parasiticus exist but not all strains produce aflatoxin. Some strains produce aflatoxin (toxigenic strains) while others do not produce aflatoxin (atoxigenic strains) (Dorner, 2009). Biological control of pre-and post-harvest aflatoxin contamination in crops has been attained by the application of competitive non-toxigenic strains of A. flavus and/or A. parasiticus. ...
... Afla-Guard™ brand obtained from a nontoxigenic A. flavus strain NRRL 21882 has been commercialized for biological control of toxigenic A. flavus strains in peanuts (Horn & Dorner, 2009). Atoxigenic A. flavus based afla-guard ® and AF36 ® have been commercialized in the United States for biological control of aflatoxin contamination in peanut, maize, and cottonseed (Bhatnagar-Mathur et al., 2015;Dorner, 2009). Atoxigenic strain of A. flavus that has the ability to displace toxigenic strains in the soil by competitive exclusion has been isolated from Nigerian soils (Atehnkeng et al., 2008;Gnonlonfin et al., 2013). ...
Article
Groundnut (Arachis hypogaea L.) is one of the most important oilseed crops in world agricultural trade. It is considered an important crop by virtue of its contribution to satisfying the protein needs of many households who cannot afford animal protein. Production and consumption of groundnuts are hampered among others, by Aspergillus flavus and Aspergillus parasiticus infection which subsequently contaminate groundnuts with aflatoxins. Aflatoxins are associated with acute and chronic toxicities in humans and animals causing induction of tumor, liver damage, liver cirrhosis, and carcinogenic, estrogenic, teratogenic, and immunosuppressive effects. Contaminated food crops expose millions of people to high risk of chronic aflatoxin exposure. Aflatoxin contamination can occur in the field before harvest, and after harvest during curing, storage and transportation. The major factors influencing A. flavus and A. parasiticus infection in groundnuts before harvest are insect damage to the developing seed/pod, drought and high soil temperatures. After harvest, environmental conditions such as high humidity and high temperatures promote fungal infection and aflatoxin accumulation. Agronomic practices such as crop rotation, use of resistant varieties, insect control, timely planting and harvesting, weed control, adequate fertilization and late season irrigation can reduce pre-harvest aflatoxin production. Additionally, atoxigenic fungi can be applied in the field to competitively displace toxigenic fungi to reduce the population of toxigenic fungi in the soil. Post-harvest aflatoxin contamination of groundnuts can be minimized by rapid and proper drying following harvesting, proper transportation and packaging, sorting and post harvest insect control. Sourcing information from different research and review articles, and book chapters, this paper provides extensive review on the predisposing factors and management of groundnut aflatoxin contamination before and after harvest.
... Previous studies have shown that sterilized grains such as rice and barley can be used as biocontrol carriers [3,4]. These starch-rich carriers provide favorable conditions for the growth and sporulation of fungi after absorbing water. ...
Article
Full-text available
Starch, alginate, and poly(N-isopropylacrylamide) (PNIPAAm) were combined to prepare a semi-interpenetrating network (IPN) hydrogel with temperature sensitivity. Calcium chloride was used as cross-linking agent, the non-toxigenic Aspergillus flavus spores were successfully encapsulated as biocontrol agents by the method of ionic gelation. Characterization of the hydrogel was performed by Fourier-transform infrared spectroscopy (FTIR), scanning electron micrograph (SEM), and thermogravimetry analysis (TGA). Formulation characteristics, such as entrapment efficiency, beads size, swelling behavior, and rheological properties were evaluated. The optical and rheological measurements indicated that the lower critical solution temperature (LCST) of the samples was about 29–30 °C. TGA results demonstrated that the addition of kaolin could improve the thermal stability of the semi-IPN hydrogel. Morphological analysis showed a porous honeycomb structure on the surface of the beads. According to the release properties of the beads, the semi-IPN hydrogel beads containing kaolin not only have the effect of slow release before peanut flowering, but they also can rapidly release biocontrol agents after flowering begins. The early flowering stage of the peanut is the critical moment to apply biocontrol agents. Temperature-sensitive hydrogel beads containing kaolin could be considered as carriers of biocontrol agents for the control of aflatoxin in peanuts.
... To date, the only cost-effective, environmentally friendly technology to reduce AF accumulation of crops is the application of atoxigenic isolates of A. flavus (lacking the AF production) as biocontrol agents to displace aflatoxigenic fungi producing AF (Dorner, 2009). Crops are typically infected by multiple A. flavus strains (Atehnkeng et al., 2016) and atoxigenic isolates applied on growing crops may compete with toxigenic strains during co-infection, and also interfere with the AF accumulation in plants. ...
Article
Full-text available
Filamentous fungi belonging to Aspergilli genera produce many compounds through various biosynthetic pathways. These compounds include a spectrum of products with beneficial medical properties (lovastatin) as well as those that are toxic and/or carcinogenic which are called mycotoxins. Aspergillus flavus, one of the most abundant soil-borne fungi, is a saprobe that is able growing on many organic nutrient sources, such as peanuts, corn and cotton seed. In many countries, food contamination by A. flavus is a huge problem, mainly due to the production of the most toxic and carcinogenic compounds known as aflatoxins. In this paper, we briefly cover current progress in aflatoxin biosynthesis and regulation, pre- and postharvest preventive measures, and decontamination procedures.
... One strategy is the application of atoxigenic strains that can out-compete the toxigenic ones. For example, the product Afla-guard®, that contains the atoxigenic strain of A. flavus NRRL 21882, was able to reduce 88% of aflatoxin contamination in peanut fields [29]. However, not all geographic areas are colonized by the same strains of Aspergillus, for example, West African A. flavus S morphotype isolates differed from North American isolates in aflatoxin type and quantity produced [30]. ...
Article
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Background Aspergillus species cause aflatoxin contamination in groundnut kernels, being a health threat in agricultural products and leading to commodity rejection by domestic and international markets. Presence of Aspergillus flavus and A. parasiticus colonizing groundnut in eastern Ethiopia, as well as presence of aflatoxins have been reported, though in this region, no genetic studies have been done of these species in relation to their aflatoxin production. Results In this study, 145 Aspergillus isolates obtained from groundnut kernels in eastern Ethiopia were genetically fingerprinted using 23 Insertion/Deletion (InDel) markers within the aflatoxin-biosynthesis gene cluster (ABC), identifying 133 ABC genotypes. Eighty-four isolates were analyzed by Ultra-Performance Liquid Chromatography (UPLC) for in vitro aflatoxin production. Analysis of genetic distances based on the approximately 85 kb-ABC by Neighbor Joining (NJ), 3D-Principal Coordinate Analysis (3D-PCoA), and Structure software, clustered the isolates into three main groups as a gradient in their aflatoxin production. Group I, contained 98% A. flavus , including L- and non-producers of sclerotia (NPS), producers of B 1 and B 2 aflatoxins, and most of them collected from the lowland-dry Babile area. Group II was a genetic admixture population of A. flavus (NPS) and A. flavus S morphotype, both low producers of aflatoxins. Group III was primarily represented by A. parasiticus and A. flavus S morphotype isolates both producers of B 1 , B 2 and G 1 , G 2 aflatoxins, and originated from the regions of Darolabu and Gursum. The highest in vitro producer of aflatoxin B 1 was A. flavus NPS N1436 (77.98 μg/mL), and the highest producer of aflatoxin G 1 was A. parasiticus N1348 (50.33 μg/mL), these isolates were from Gursum and Darolabu, respectively. Conclusions To the best of our knowledge, this is the first study that combined the use of InDel fingerprinting of the ABC and corresponding aflatoxin production capability to describe the genetic diversity of Aspergillus isolates from groundnut in eastern Ethiopia. Three InDel markers, AFLC04, AFLC08 and AFLC19, accounted for the main assignment of individuals to the three Groups; their loci corresponded to aflC ( pksA ), hypC , and aflW ( moxY ) genes, respectively. Despite InDels within the ABC being often associated to loss of aflatoxin production, the vast InDel polymorphism observed in the Aspergillus isolates did not completely impaired their aflatoxin production in vitro.
... For AF36, a point mutation in the aflatoxin biosynthesis gene pksA (aflC) is responsible for the AF− phenotype [1], while the Afla-Guard ® strain (NRRL21882) is missing most of the genes in the 80 kb aflatoxin biosynthesis gene cluster up to the proximal telomere on chromosome 3 [2,3]. Field trials have shown that proper application of spores from these fungi greatly reduces the incidence of aflatoxin contamination in corn [4], cottonseed [5], and peanuts [6], and is being considered for use against contamination of tree nuts. The ability of these strains to reduce aflatoxin contamination has been postulated to be due to displacement of the aflatoxin-producing populations in the soil [5]. ...
Article
Current biological control methods to prevent pre-harvest aflatoxin contamination of corn, cottonseed, and ground and tree nuts involve field inoculation of non-aflatoxigenic Aspergillus flavus. To date, the efficacy of this approach requires annual reapplication of the biocontrol agent. The reason for this requirement is uncertain. To track the dispersal and test the longevity of these strains, we prepared fluorescent biocontrol strains by incorporating into them the gene expressing the enhanced green fluorescent protein (eGFP). We first investigated the effects of eGFP transformation on the ability of the fluorescent fungus to compete with its non-fluorescent homolog, and then with other heterologous non-aflatoxigenic strains as well as with aflatoxigenic isolates. Our findings indicate that, in these studies, detection of fluorescence was variable, with some fluorescent strains exhibiting enhanced growth and sporulation post-transformation. In our tests, not all transformed strains proved to be good candidates for tracking because their fluorescence was reduced over the course of our study. Most of the transformed strains retained fluorescence and showed robust colony growth in an artificial competitor environment; therefore, they should be suited for further trial under more natural settings. Our ultimate objective is to determine if out-crossing between biocontrol strains and native field populations is occurring in a natural setting.
... It is influenced by soil factor that harder and extreme weather, dry condition, germ, availability of superior seeds, etc. Peanut as a part of food self-supporting of Indonesia is a commodity which still low production in farmer level (Liptan IP2TP, 2004). For increasing these production is needed system completing of peanut cultivation with application of cultivation technology and modern technology for supplying of superior seeds (Domer, 2009). This method is application of multigamma radiation for breeding of local peanut to obtain several superior seeds on multiculture system, that tolerant to abiotic and biotic conditions, specially dry condition, in order that attained optimal production. ...
Article
The main problems investigated in these research are 1) the developing of local peanut variety from west Sumba through breeding with multigamma radiation method (nuclear) and carefully selection on two varieties of peanut, i.e erect peanut and creep peanut by multiculture principle, in order to obtain the primer seed of local peanut variety that can increase production, 2) developing of primer seed of local yellow corn, in order to tolerant to abiotic and biotic conditions. The main method of research is application of multigamma radiation that supported by other methods comprised of observation/survey, sampling, multiculture, analysis, comparison, and interpretation. The results of research are two primer varieties of local peanut seed from East Sumba with principle multiculture by multigamma radiation and carefully selection, and the primer seed of sweet local corn that tolerant to abiotic and biotic conditions, in order that production results of peanut’s farmer and local corn in East Sumba specially and NNT generally, can significantly optimally increase, to support the stamina and safety of National food. The average production is obtained 5.7 ton/ha and 4.5 ton/ha for erect peanut, or the average production increase 43.86% for creep peanut and 42.22% for erect peanut. On the second planting (first cleansing), the research on the second year, obtained the increase of average production about 45.84% (percent) of dried pod for erect peanut and 46.67% (percent) of dry pod for creep peanut. The increase of production potential on the second planting, the research on the second year in succession is 52.29% (percent) dried pod dried pod for erect peanut, and 52.22% (percent) dried pod for creep peanut. The increase average of production on the second year of research is 40.25% (percent) dried pod for erect peanut, and 40.42% (percent) dried pod for creep peanut. The increase average of production potential 48.84% (percent) dry pod for erect peanut, and 49.95% (percent) dried pod for creep peanut.
... Significant and consistent reductions in aflatoxin contamination (70-90%) have been observed in peanut and cotton field experiments using such non-toxigenic Aspergillus strains [26]. Two commercial products (afla-guard ® and AF36 ® ) based on atoxigenic A. flavus strains have been approved in the U.S. by the Environmental Protection Agency for biological prevention of aflatoxin contamination in peanut, maize, and cottonseed [27]. A few African atoxigenic strains of A. flavus have also been identified that competitively exclude toxigenic fungi in maize and peanut fields. ...
... A point mutation in the pksA (aflC) aflatoxin pathway gene, leading to early translational termination, is responsible for the AF− phenotype of AF36 (Ehrlich and Cotty, 2004), while the Afla-Guard strain (NRRL21882) has a deletion spanning from within the aflatoxin cluster to the proximal telomere on chromosome 3 (Chang et al., 2005). Regular application of these AF− strains has been shown, with varied extents of efficacy, to reduce the incidence of aflatoxin contamination in maize (Dorner, 2009a), cottonseed (Cotty, 1994), and groundnuts (Dorner, 2009b), and AF36 is now being tested for use against contamination of tree nuts (Doster et al., 2012). Several theories have been developed to explain the ability of these strains to reduce aflatoxin contamination that include: displacement of the aflatoxin-producing populations in the soil (Ehrlich and Cotty, 2004); nutrient sequestration through competitive exclusion (Mehl and Cotty, 2013); and possible response to contact (thigmotropism) between the AF− isolate and an aflatoxigenic (AF+) isolate leading to inhibition of aflatoxin production (Huang et al., 2011). ...
Article
Field inoculation with non-aflatoxigenic Aspergillus flavus is a preferred method for pre-harvest biocontrol of aflatoxin contamination of maize, cottonseed, and groundnut. Rationale for using these A. flavus strains is that they (1) maintain persistent control of aflatoxigenic fungi in the field, and (2) are incapable of out-crossing. Trackable field-released biocontrol strains will be beneficial to study the movement and longevity of non-aflatoxigenic A. flavus strains. Incorporating a naturally-occurring compound such as enhanced green fluorescent protein (eGFP) into a biocontrol strain might allow observation of its behaviour in field settings. The success of long-term field testing of eGFP-expressing A. flavus strains depends on their ability to maintain fluorescence throughout growth. Additionally, to ensure accurate tracking of the fluorescent atoxigenic strain, the likelihood of their out-crossing with individuals from the native population must be determined. In vitro mating experiments paired each of six different eGFP-transformed atoxigenic strains with a highly fertile toxigenic A. flavus isolate. Findings indicate that the eGFP gene, and possibly the aflatoxin cluster, is heritable by the F1 progeny. Not all cultured ascospores were fluorescent, but subsequent growth arising from a single fluorescent ascospore exhibited fluorescence similar to the eGFP parent. Observed mixed-fluorescence among conidia in a single chain suggests heterokaryosis at the moment of conidiogenesis. Mycotoxin assays showed that some fluorescent F1 individuals produce aflatoxin and/or cyclopiazonic acid which would indicate they are recombinant offspring. The findings in this laboratory study lend support to concern that atoxigenic strains are not impervious to genetic recombination and for which, if possible in a natural environment, repeated use could pose a risk of increasing the occurrence of aflatoxigenic individuals in treated fields.
... Biological control is emerging as an effective approach for reducing aflatoxin contamination and Aspergillus infection under preharvest and postharvest conditions in groundnut (Dorner & Cole, 2002;Dorner et al., 2003). Several organisms including bacteria, yeasts and non-aflatoxigenic/atoxigenic strains of A. flavus had been tested for the control of aflatoxin contamination of which only atoxigenic strains were proved successful and have reached the commercial stage (Brown et al., 1991;Cotty, 1994;Yin et al., 2008;Dorner, 2009). In recent years, some antagonists were tested for the biocontrol of postharvest diseases of agricultural commodities. ...
Article
The potential of root-colonising antagonistic microbial biocontrol agents was evaluated for their ability to improve plant growth and suppress aflatoxigenic fungal and aflatoxin contamination in groundnut. By considering root colonisation of groundnut seedlings, plant growth promotion and antagonism against aflatoxigenic Aspergillus flavus as preliminary criteria, eight rhizobacteria and nine Trichoderma spp. were selected and characterised for their beneficial traits. These strains gave varying results for IAA production, phosphate solubilisation, ACC deaminase, chitinase and siderophore production. Under laboratory and greenhouse conditions, these strains significantly (P < 0.05) suppressed seed-borne and rhizospheric population of A. flavus and improved seed quality variables. However, cdELISA results revealed that none of the biocontrol strains were effective in reducing aflatoxin level in seed. Based on the overall performance, Pseudomonas fluorescens 2bpf, Bacillus sp. Bsp-3/aM and Trichoderma atroviride UMDBT-Dha.Tat8 were used for field trials in the form of talcum powder formulations. Under field conditions, biocontrol agents improved seedling emergence, plant biomass and pod yield. Seeds harvested from plots treated with biocontrol agents showed significant (P < 0.05) reduction in A. flavus infection and aflatoxin production after 6 months' storage. Use of microbial strains with multiple beneficial traits is advantageous in bioformulation development. Hence, in future, these formulations will play a major role as biofertilisers and biopesticides, which can reduce the usage of agrochemicals up to greater extents in groundnut production.
... Currently, there are no commercially available fungal cultivars resistant to the infection by A. flavus. The only promising intervention method showing measurable extents of control of aflatoxin contamination is to use biological control, which includes applying atoxigenic A. flavus strains, such as AF36 [2], K49 [3] or Afla-Guard ® [4], to outcompete toxigenic strains in the field or spraying a yeast formulation to pistachio trees to prevent fungal growth [5]. In field tests, these biocontrol approaches have achieved greater than 80 percent reduction in aflatoxin contamination. ...
Article
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The saprophytic soil fungus Aspergillus flavus infects crops and produces aflatoxin. Pichia anomala, which is a biocontrol yeast and produces the major volatile 2-phenylethanol (2-PE), is able to reduce growth of A. flavus and aflatoxin production when applied onto pistachio trees. High levels of 2-PE are lethal to A. flavus and other fungi. However, at low levels, the underlying mechanism of 2-PE to inhibit aflatoxin production remains unclear. In this study, we characterized the temporal transcriptome response of A. flavus to 2-PE at a subinhibitory level (1 μL/mL) using RNA-Seq technology and bioinformatics tools. The treatment during the entire 72 h experimental period resulted in 131 of the total A. flavus 13,485 genes to be significantly impacted, of which 82 genes exhibited decreased expression. They included those encoding conidiation proteins and involved in cyclopiazonic acid biosynthesis. All genes in the aflatoxin gene cluster were also significantly decreased during the first 48 h treatment. Gene Ontology (GO) analyses showed that biological processes with GO terms related to catabolism of propionate and branched-chain amino acids (valine, leucine and isoleucine) were significantly enriched in the down-regulated gene group, while those associated with ribosome biogenesis, translation, and biosynthesis of α-amino acids were over-represented among the up-regulated genes. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that metabolic pathways negatively impacted among the down-regulated genes parallel to those active at 30 °C, a condition conducive to aflatoxin biosynthesis. In contrast, metabolic pathways positively related to the up-regulated gene group resembled those at 37 °C, which favors rapid fungal growth and is inhibitory to aflatoxin biosynthesis. The results showed that 2-PE at a low level stimulated active growth of A. flavus but concomitantly rendered decreased activities in branched-chain amino acid degradation. Since secondary metabolism occurs after active growth has ceased, this growth stimulation resulted in suppression of expression of aflatoxin biosynthesis genes. On the other hand, increased activities in degradation pathways for branched-chain amino acids probably are required for the activation of the aflatoxin pathway by providing building blocks and energy regeneration. Metabolic flux in primary metabolism apparently has an important role in the expression of genes of secondary metabolism.
... The use of atoxigenic VCGs of A. flavus as biocontrol agents of toxigenic isolates to reduce aflatoxin contamination of agricultural commodities is a common practice in the US (Cotty et al., 2008;Dorner, 2008). However, systematic studies to improve the use of indigenous atoxigenic isolates of A. flavus in Africa to reduce aflatoxin contamination in maize are still lacking. ...
Article
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Maize infected by aflatoxin-producing Aspergillus flavus may become contaminated with aflatoxins, and as a result, threaten human health, food security and farmers' income in developing countries where maize is a staple. Environmental distribution and genetic diversity of A. flavus can influence the effectiveness of atoxigenic isolates in mitigating aflatoxin contamination. However, such information has not been used to facilitate selection and deployment of atoxigenic isolates. A total of 35 isolates of A. flavus isolated from maize samples collected from three agro-ecological zones of Nigeria were used in this study. Ecophysiological characteristics, distribution and genetic diversity of the isolates were determined to identify vegetative compatibility groups (VCGs). The generated data were used to inform selection and deployment of native atoxigenic isolates to mitigate aflatoxin contamination in maize. In co-inoculation with toxigenic isolates, atoxigenic isolates reduced aflatoxin contamination in grain by > 96%. A total of 25 VCGs were inferred from the collected isolates based on complementation tests involving nitrate non-utilizing (nit(-) ) mutants. To determine genetic diversity and distribution of VCGs across agro-ecological zones, 832 nit(-) mutants from 52 locations in 11 administrative districts were paired with one self-complementary nitrate auxotroph tester-pair for each VCG. Atoxigenic VCGs accounted for 81.1% of the 153 positive complementations recorded. Genetic diversity of VCGs was highest in the derived savannah agro-ecological zone (H = 2.61) compared with the southern Guinea savannah (H = 1.90) and northern Guinea savannah (H = 0.94) zones. Genetic richness (H = 2.60) and evenness (E5 = 0.96) of VCGs were high across all agro-ecological zones. Ten VCGs (40%) had members restricted to the original location of isolation, whereas 15 VCGs (60%) had members located between the original source of isolation and a distance > 400 km away. The present study identified widely distributed VCGs in Nigeria such as AV0222, AV3279, AV3304 and AV16127, whose atoxigenic members can be deployed for a region-wide biocontrol of toxigenic isolates to reduce aflatoxin contamination in maize.
... The use of atoxigenic VCGs of A. flavus as biocontrol agents of toxigenic isolates to reduce aflatoxin contamination of agricultural commodities is a common practice in the US (Cotty et al., 2008;Dorner, 2008). However, systematic studies to improve the use of indigenous atoxigenic isolates of A. flavus in Africa to reduce aflatoxin contamination in maize are still lacking. ...
... Among known mycotoxins, aflatoxins produced by fungi Aspergillus flavus Link and Aspergillus parasiticus Speare pose the greatest threat to human and animal health [19,35]. Four major aflatoxins (AFB1, AFB2, AFG1 and AFG2) are common contaminants of food and feed [15]. Aflatoxin B1 (AFB1) is the most toxic mycotoxin and has been classified as a Class 1 human carcinogen by the International Agency for Research on Cancer [26]. ...
Article
One of the most promising management tools to reduce mycotoxins in food and feed is the pre-harvest biological control of mycotoxigenic fungi using microbes. The goal of this investigation was to evaluate the potential of a stain of Trichoderma harzianum, T77, for control of Aspergillus flavus on sweetcorn. Under greenhouse and field conditions, T. harzianum was applied as a pre-harvest spray treatment to silks of sweetcorn plants at 1, 3, 6, 8, 10, 12 and 14 days post-midsilk. Toxigenic A. flavus was spray inoculated as a conidial suspension (10³ spores ml⁻¹) onto silks at 2, 4, 7, 9, 11 and 13 days post-midsilk. Percentage kernel infection, disease ratings, ELISA and HPLC analyses were used to quantify A. flavus infection and aflatoxin contamination. There was a significant reduction in toxigenic A. flavus infection and aflatoxin contamination after silk spray treatments with T77 at 10 and 12 days post-midsilk. In vitro dual culture bioassays and ultrastructural studies using environmental scanning electron microscopy revealed antibiosis and mycoparasitism are the probable modes of action. It thus can be seen that pre-harvest spray treatment of sweetcorn at the silk growth stage can reduce the level of A. flavus contamination of grain. An integrated approach consisting pre-harvest biological control using selected strains of T. harzianum in conjunction with other post-harvest management strategies could reduce A. flavus infection and aflatoxin contamination in grain.
... Several strains of B. subtilis and P. solanacearum isolated from the non-rhizosphere of maize soil have been reported to eliminate aflatoxin (Nesci et al., 2005). Biological control of aflatoxin production in crops in the US has been approved by the Environmental Protection Agency and two commercial products based on atoxigenic A. flavus strains are being used (Afla-guard R and AF36 R ) for the prevention of aflatoxin in peanuts, corn, and cotton seed (Dorner, 2009). Good agricultural practices (GAPs) also help control the toxins to a larger extent, such as timely planting, providing adequate plant nutrition, controlling weeds, and crop rotation, which effectively control A. flavus infection in the field (Ehrlich and Cotty, 2004;Waliyar et al., 2013). ...
Article
Full-text available
The aflatoxin producing fungi, Aspergillus spp., are widely spread in nature and have severely contaminated food supplies of humans and animals, resulting in health hazards and even death. Therefore, there is great demand for aflatoxins research to develop suitable methods for their quantification, precise detection and control to ensure the safety of consumers’ health. Here, the chemistry and biosynthesis process of the mycotoxins is discussed in brief along with their occurrence, and the health hazards to humans and livestock. This review focuses on resources, production, detection and control measures of aflatoxins to ensure food and feed safety. The review is informative for health-conscious consumers and research experts in the fields. Furthermore, providing knowledge on aflatoxins toxicity will help in ensure food safety and meet the future demands of the increasing population by decreasing the incidence of outbreaks due to aflatoxins.
... Competitive exclusion of aflatoxinproducing fungi by endemic atoxigenic VCGs is a proven non-toxic biological control technology which reduces aflatoxins during both crop development and post-harvest storage, as well as throughout the value chain (Cotty et al., 2007;Atehnkeng et al., 2014;Bandyopadhyay et al., 2016). Two biocontrol products containing atoxigenic strain active ingredients -Aspergillus flavus AF36 and Afla-Guard® -are registered for use in the United States, where large acreages of cottonseed, maize, groundnut and pistachios are treated with these biocontrol products annually (Cotty et al., 2008;Dorner, 2009;Weaver et al., 2015). ...
... A promising strategy is the field application of atoxigenic A. flavus strains to reduce aflatoxin content in crops. In the United States and several African countries, driven primarily by USDA-ARS and IITA, respectively, the application of carefully selected atoxigenic A. flavus strains as biocontrol agents has consistently reduced aflatoxin contamination in commercially produced crops and allowed farmers to enter domestic and international premium markets (Cotty et al., 2007;Dorner, 2009;Mehl et al., 2012;Doster et al., 2014;Bandyopadhyay et al., 2019;Ortega-Beltran and Bandyopadhyay, 2019;Schreurs et al., 2019;Senghor et al., 2019). When applied at the right stage, treated crops accumulate over 80% less and sometimes even 100% less aflatoxin than non-treated adjacent crops. ...
Article
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Aflatoxins are secondary metabolites produced by soilborne saprophytic fungus Aspergillus flavus and closely related species that infect several agricultural commodities including groundnut and maize. The consumption of contaminated commodities adversely affects the health of humans and livestock. Aflatoxin contamination also causes significant economic and financial losses to producers. Research efforts and significant progress have been made in the past three decades to understand the genetic behavior, molecular mechanisms, as well as the detailed biology of host-pathogen interactions. A range of omics approaches have facilitated better understanding of the resistance mechanisms and identified pathways involved during host-pathogen interactions. Most of such studies were however undertaken in groundnut and maize. Current efforts are geared toward harnessing knowledge on host-pathogen interactions and crop resistant factors that control aflatoxin contamination. This study provides a summary of the recent progress made in enhancing the understanding of the functional biology and molecular mechanisms associated with host-pathogen interactions during aflatoxin contamination in groundnut and maize.
... Such microorganisms include bacteria, algae and fungi Brimner and Boland (2003). __________________________________________________ 3 Recently, the only promising method of control of aflatoxin contamination is to use biological control, which includes applying a toxigenic A. flavus strains Cotty (1994), Dorner (2009) and Abbas et al. (2011, to outcompete toxigenic strains in the field or spraying a yeast formulation to prevent fungal growth Hua (2006). In field tests, these biocontrol approaches have achieved greater than 80 percent reduction in aflatoxin contamination. ...
Conference Paper
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The present study was undertaken to evaluate the efficacy of bio-control on structures and regulatory genes in the biosynthetic pathway (aflD and aflO) and the production of aflatoxin B 1 (AFB 1) by aflatoxigenic A. flavus that recovered from animal's feeds. A total of 100 samples (25 of each) of consumed animal's feeds, water, litters and walls of animal's houses halls, from a private farm of cattle at Giza Governorate in which the cattle calves suffered from symptoms of toxicosis as vomiting and profuse diarrhea and related environmental factors were investigated for fungal and aflatoxin pollution. The mould of A. flavus was recovered from (80%, 20%, 12% and 4%) of environmental factors of diseased animal's (feeds, water, litters and walls), respectively. All A. flavus that recovered only from animal's feeds 100% were aflatoxigenic. While, the highest total aflatoxin residues only were detected also in animal's feeds samples (100 %). Whereas, the maximum levels of AFTs were detected in (animal's feeds) (20 ppm) and the minimum amount were (2.0 ppm), with a mean level of (10.4 ± 4.91ppm). The bio-control of A. flavus by bacteria (B. subtillus) and yeast (C. albicans) were evaluated by biochemical and molecular detection of the changes in AFT-s genes production (aflD and aflO). All treated isolates of A. flavus were inhibited their ability for AFTs production as detected by chemical chromatographic method. However, the extraction of DNA from these treated isolates showed that the responsible AFTs biosynthesis genes (aflO and aflD) detected by PCR method in control non-treated A. flavus. Whereas, the same isolates were negative for AFTs biosynthesis genes (aflO, aflD) and completely eliminated after bio-control. These results indicated the efficacy of bio-control which caused inactivation and removal of regulatory gene in the biosynthetic pathway (aflD and aflO) and the production of AFB 1 ‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬
... Such microorganisms include bacteria, algae and fungi Brimner and Boland (2003). __________________________________________________ 3 Recently, the only promising method of control of aflatoxin contamination is to use biological control, which includes applying a toxigenic A. flavus strains Cotty (1994), Dorner (2009) and Abbas et al. (2011, to outcompete toxigenic strains in the field or spraying a yeast formulation to prevent fungal growth Hua (2006). In field tests, these biocontrol approaches have achieved greater than 80 percent reduction in aflatoxin contamination. ...
Article
Full-text available
The present study was undertaken to evaluate the efficacy of bio-control on structures and regulatory genes in the biosynthetic pathway (aflD and aflO) and the production of aflatoxin B 1 (AFB 1) by aflatoxigenic A. flavus that recovered from animal's feeds. A total of 100 samples (25 of each) of consumed animal's feeds, water, litters and walls of animal's houses halls, from a private farm of cattle at Giza Governorate in which the cattle calves suffered from symptoms of toxicosis as vomiting and profuse diarrhea and related environmental factors were investigated for fungal and aflatoxin pollution. The mould of A. flavus was recovered from (80%, 20%, 12% and 4%) of environmental factors of diseased animal's (feeds, water, litters and walls), respectively. All A. flavus that recovered only from animal's feeds 100% were aflatoxigenic. While, the highest total aflatoxin residues only were detected also in animal's feeds samples (100 %). Whereas, the maximum levels of AFTs were detected in (animal's feeds) (20 ppm) and the minimum amount were (2.0 ppm), with a mean level of (10.4 ± 4.91ppm). The bio-control of A. flavus by bacteria (B. subtillus) and yeast (C. albicans) were evaluated by biochemical and molecular detection of the changes in AFT-s genes production (aflD and aflO). All treated isolates of A. flavus were inhibited their ability for AFTs production as detected by chemical chromatographic method. However, the extraction of DNA from these treated isolates showed that the responsible AFTs biosynthesis genes (aflO and aflD) detected by PCR method in control non-treated A. flavus. Whereas, the same isolates were negative for AFTs biosynthesis genes (aflO, aflD) and completely eliminated after bio-control. These results indicated the efficacy of bio-control which caused inactivation and removal of regulatory gene in the biosynthetic pathway (aflD and aflO) and the production of AFB 1 ‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬
... The carrier materials that increase the storability of the products generally include fine clay, peat, talc, lignite, alginate, polyacrylamide beads, starch, diatomaceous earth, vermiculite, cellulose (carboxymethyl cellulose), and polymers, especially xanthan gum (Digat, 1991;Harman and Custis, 2006). Furthermore, in various local conditions, charcoal, farmyard manure, vermicompost, compost, bagasse, press mud, and sterilized grains such as rice, corn, millet and barley have also been successfully used as carriers for different kinds of microorganisms (Connick et al., 1991;Schisler et al., 2004;Pitt and Hocking, 2006;Dorner, 2009;Harman et al., 2010). ...
Article
Full-text available
Plants exist in close association with uncountable numbers of microorganisms around, on, and within them. Some of these endophytically colonize plant roots. The colonization of roots by certain symbiotic strains of plant-associated bacteria and fungi results in these plants performing better than plants whose roots are colonized by only the wild populations of microbes. We consider here crop plants whose roots are inhabited by introduced organisms, referring to them as Enhanced Plant Holobionts (EPHs). EPHs frequently exhibit resistance to specific plant diseases and pests (biotic stresses); resistance to abiotic stresses such as drought, cold, salinity, and flooding; enhanced nutrient acquisition and nutrient use efficiency; increased photosynthetic capability; and enhanced ability to maintain efficient internal cellular functioning. The microbes described here generate effects in part through their production of Symbiont-Associated Molecular Patterns (SAMPs) that interact with receptors in plant cell membranes. Such interaction results in the transduction of systemic signals that cause plant-wide changes in the plants’ gene expression and physiology. EPH effects arise not only from plant-microbe interactions, but also from microbe-microbe interactions like competition, mycoparasitism, and antibiotic production. When root and shoot growth are enhanced as a consequence of these root endophytes, this increases the yield from EPH plants. An additional benefit from growing larger root systems and having greater photosynthetic capability is greater sequestration of atmospheric CO2. This is transferred to roots where sequestered C, through exudation or root decomposition, becomes part of the total soil carbon, which reduces global warming potential in the atmosphere. Forming EPHs requires selection and introduction of appropriate strains of microorganisms, with EPH performance affected also by the delivery and management practices.
... Biological control of aflatoxin contamination is based on the premise that atoxigenic strains will displace naturally occurring toxigenic strains from infection sites when high densities of the atoxigenic strains are applied to the soil. Consistent reductions in aflatoxin contamination ranging from 67 to 99% due to atoxigenic strains have been reported (Alaniz Zanon et al. 2013;Atehnkeng et al. 2014;Dorner 2009;Mauro et al. 2018). While there has been considerable progress in identifying host genes for preventing aflatoxin contamination in several crops, progress has been slow and there are no commercially acceptable aflatoxin resistant cultivars (Fountain et al. 2015;Warburton and Williams 2014). ...
Article
Aspergillus flavus is a morphologically complex species that can produce the group of polyketide derived carcinogenic and mutagenic secondary metabolites, aflatoxins, as well as other secondary metabolites such as cyclopiazonic acid and aflatrem. Aflatoxin causes aflatoxicosis when aflatoxins are ingested through contaminated food and feed. In addition, aflatoxin contamination is a major problem, from both an economic and health aspect, in developing countries, especially Asia and Africa, where cereals and peanuts are an important food crops. Early measures for control of A. flavus infection and consequent aflatoxin contamination centered on creating unfavorable environments for the pathogen and destroying contaminated products. While development of atoxigenic (non-aflatoxin producing) strains of A. flavus as viable commercial biocontrol agents has marked a unique advance for control of aflatoxin contamination, particularly in Africa, new insights into the biology and sexuality of A. flavus are now providing opportunities to design improved atoxigenic strains for sustainable biocontrol of aflatoxin. Further, progress in the use of molecular technologies such as incorporation of antifungal genes in the host and host-induced gene silencing, is providing knowledge that could be harnessed to develop germplasm that is resistant to infection by A. flavus and aflatoxin contamination. This review summarizes the substantial progress that has been made to understand the biology of A. flavus and mitigate aflatoxin contamination with emphasis on maize. Concepts developed to date can provide a basis for future research efforts on the sustainable management of aflatoxin contamination.
... A promising strategy is the field application of atoxigenic A. flavus strains to reduce aflatoxin content in crops. In the United States and several African countries, driven primarily by USDA-ARS and IITA, respectively, the application of carefully selected atoxigenic A. flavus strains as biocontrol agents has consistently reduced aflatoxin contamination in commercially produced crops and allowed farmers to enter domestic and international premium markets (Cotty et al., 2007;Dorner, 2009;Mehl et al., 2012;Doster et al., 2014;Bandyopadhyay et al., 2019;Ortega-Beltran and Bandyopadhyay, 2019;Schreurs et al., 2019;Senghor et al., 2019). When applied at the right stage, treated crops accumulate over 80% less and sometimes even 100% less aflatoxin than non-treated adjacent crops. ...
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Aflatoxins are secondary metabolites produced by soilborne saprophytic fungus Aspergillus flavus and closely related species that infect several agricultural commodities including groundnut and maize. The consumption of contaminated commodities adversely affects the health of humans and livestock. Aflatoxin contamination also causes significant economic and financial losses to producers. Research efforts and significant progress have been made in the past three decades to understand the genetic behavior, molecular mechanisms, as well as the detailed biology of host-pathogen interactions. A range of omics approaches have facilitated better understanding of the resistance mechanisms and identified pathways involved during host-pathogen interactions. Most of such studies were however undertaken in groundnut and maize. Current efforts are geared toward harnessing knowledge on host-pathogen interactions and crop resistant factors that control aflatoxin contamination. This study provides a summary of the recent progress made in enhancing the understanding of the functional biology and molecular mechanisms associated with host-pathogen interactions during aflatoxin contamination in groundnut and maize.
... A promising strategy is the field application of atoxigenic A. flavus strains to reduce aflatoxin content in crops. In the United States and several African countries, driven primarily by USDA-ARS and IITA, respectively, the application of carefully selected atoxigenic A. flavus strains as biocontrol agents has consistently reduced aflatoxin contamination in commercially produced crops and allowed farmers to enter domestic and international premium markets (Cotty et al., 2007;Dorner, 2009;Mehl et al., 2012;Doster et al., 2014;Bandyopadhyay et al., 2019;Ortega-Beltran and Bandyopadhyay, 2019;Schreurs et al., 2019;Senghor et al., 2019). When applied at the right stage, treated crops accumulate over 80% less and sometimes even 100% less aflatoxin than non-treated adjacent crops. ...
Article
Full-text available
Aflatoxins are secondary metabolites produced by soilborne saprophytic fungus Aspergillus flavus and closely related species that infect several agricultural commodities including groundnut and maize. The consumption of contaminated commodities adversely affects the health of humans and livestock. Aflatoxin contamination also causes significant economic and financial losses to producers. Research efforts and significant progress have been made in the past three decades to understand the genetic behavior, molecular mechanisms, as well as the detailed biology of host-pathogen interactions. A range of omics approaches have facilitated better understanding of the resistance mechanisms and identified pathways involved during host-pathogen interactions. Most of such studies were however undertaken in groundnut and maize. Current efforts are geared toward harnessing knowledge on host-pathogen interactions and crop resistant factors that control aflatoxin contamination. This study provides a summary of the recent progress made in enhancing the understanding of the functional biology and molecular mechanisms associated with host-pathogen interactions during aflatoxin contamination in groundnut and maize.
... The US Department of Agriculture -Agricultural Research Service (USDA-ARS) developed the first atoxigenic biocontrol product, Aspergillus flavus AF36, and initially registered it with the US Environmental Protection Agency (USEPA) for use in cotton (USEPA, 2003(USEPA, , 2004. Together with Afla-Guard R , a second atoxigenic biocontrol product, the biocontrol technology has been used commercially for >15 years in the US in several crops (Cotty et al., 2007;Dorner, 2009;Doster et al., 2014;Ortega-Beltran and Bandyopadhyay, 2019). ...
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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.
... Application of manure has also been shown to reduce aflatoxin contamination [44,131]. Further research has confirmed that biocontrol using non-aflatoxigenic A. flavus and A. parasiticus strains significantly reduce aflatoxin contamination in groundnuts and maize [132,133]. ...
Article
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Aflatoxin is considered a "hidden poison" due to its slow and adverse effect on various biological pathways in humans, particularly among children, in whom it leads to delayed development, stunted growth, liver damage, and liver cancer. Unfortunately, the unpredictable behavior of the fungus as well as climatic conditions pose serious challenges in precise phenotyping, genetic prediction and genetic improvement, leaving the complete onus of preventing aflatoxin contamination in crops on post-harvest management. Equipping popular crop varieties with genetic resistance to aflatoxin is key to effective lowering of infection in farmer's fields. A combination of genetic resistance for in vitro seed colonization (IVSC), pre-harvest aflatoxin contamination (PAC) and aflatoxin production together with pre-and post-harvest management may provide a sustainable solution to aflatoxin contamination. In this context, modern "omics" approaches, including next-generation genomics technologies, can provide improved and decisive information and genetic solutions. Preventing contamination will not only drastically boost the consumption and trade of the crops and products across nations/regions, but more importantly, stave off deleterious health problems among consumers across the globe. Key Contribution: This article provides an overview on the complex molecular regulatory events associated with the aflatoxin resistance mechanisms in groundnut. Emphasis is placed for more research on discovery of resistant lines, markers, genes and pathways which together with pre-and post-harvest management practices can mitigate aflatoxin contamination in groundnuts.
... Application of manure has also been shown to reduce aflatoxin contamination [44,131]. Further research has confirmed that biocontrol using non-aflatoxigenic A. flavus and A. parasiticus strains significantly reduce aflatoxin contamination in groundnuts and maize [132,133]. ...
Article
Full-text available
Aflatoxin is considered a “hidden poison” due to its slow and adverse effect on various biological pathways in humans, particularly among children, inwhomit leads to delayed development, stunted growth, liver damage, and liver cancer. Unfortunately, the unpredictable behavior of the fungus as well as climatic conditions pose serious challenges in precise phenotyping, genetic prediction and genetic improvement, leaving the complete onus of preventing aflatoxin contamination in crops on post-harvest management. Equipping popular crop varieties with genetic resistance to aflatoxin is key to effective lowering of infection in farmer’s fields. A combination of genetic resistance for in vitro seed colonization (IVSC), pre-harvest aflatoxin contamination (PAC) and aflatoxin production together with pre- and post-harvest management may provide a sustainable solution to aflatoxin contamination. In this context, modern “omics” approaches, including next-generation genomics technologies, can provide improved and decisive information and genetic solutions. Preventing contamination will not only drastically boost the consumption and trade of the crops and products across nations/regions, but more importantly, stave off deleterious health problems among consumers across the globe.
... Moreover, biocontrol treatments were effectively reduced aflatoxin contamination between 93.23 and 95.82% under drying and pre-storage periods. The treatment to the soil of nontoxigenic strains of Aspergillus both decrease levels of preharvest aflatoxin contamination on peanuts (Cole et al., 1989;Dorner et al., 1992;Dorner et al., 1998;Dorner, 2004;Dorner, 2005), and also has a carry-forward impact, decreasing aflatoxin contamination that would be occur during storage (Dorner and Cole, 2002;Dorner, 2009). Dorner (2004) reported that plots of treated and not treated with nontoxigenic strains in 1998 peanut field research were stored in a warehouse and exposed to the storage conditions that could be contaminated with aflatoxin. ...
Article
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This study was carried out to determine the efficacy of different applications of a biopesticide for reduction of aflatoxin contamination in peanut. The biopesticide, afla-guard, delivers a nontoxigenic Aspergillus flavus to the field where it competes with naturally occurring toxigenic fungus. Biocontrol treatments included: (ı) soil application during sowing, (ıı) multiple application during sowing and 40 days after planting, (ııı) foliar application at 60 days after planting (ıv) control (untreated plots). Biopesiticide was applied to peanut plots in 2015 and 2016 in Randomized Complete Block Design with four replications. Peanuts were collected from control and treated plots at harvest-drying-pre-storage periods and analysed for aflatoxins. Aflatoxin concentrations were generally quite low in 2015, also the aflatoxin concentration in treated samples (from 0.04 to 0.71 µg/kg) was reduced by 97.38 to 99.82% compared with controls (from 21.84 to 27.12 µg/kg). In 2016, reductions were also noted for all biocontrol treatments (from 89.07 to 92.39%) compared with controls. In conjunction with the reductions in aflatoxin contamination, biocontrol treatments produced significant reductions with biopesticide in peanut. Therefore, it can be said that a biological control method is a promising approach for controlling aflatoxin.
... Biocontrol strains are often referred to as "atoxigenic" (Bandyopadhyay et al. 2016, 771;Grubisha and Cotty 2015, 5889;Mauro et al. 2018, 1;Moore et al. 2015, 301;Ortega-Beltran et al. 2019, 905; Weaver and Abbas 2019, 1), "nontoxic" (Cole and Cotty 1990, 63), or "non-toxigenic" (Cole and Cotty 1990, 64;Dorner 2009;Gasperini et al. 2019) when they are non-aflatoxigenic at best (King et al. 2011). Their inability to produce aflatoxins does not mean nonaflatoxigenic fungi are incapable of producing other mycotoxins (Kagot et al. 2019). ...
Article
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There is an important reason for the accelerated use of non-aflatoxigenic Aspergillus flavus to mitigate pre-harvest aflatoxin contamination… it effectively addresses the imperative need for safer food and feed. Now that we have decades of proof of the effectiveness of A. flavus as biocontrol, it is time to improve several aspects of this strategy. If we are to continue relying heavily on this form of aflatoxin mitigation, there are considerations we must acknowledge, and actions we must take, to ensure that we are best wielding this strategy to our advantage. These include its: (1) potential to produce other mycotoxins, (2) persistence in the field in light of several ecological factors, (3) its reproductive and genetic stability, (4) the mechanism(s) employed that allow it to elicit control over aflatoxigenic strains and species of agricultural importance and (5) supplemental alternatives that increase its effectiveness. There is a need to be consistent, practical and thoughtful when it comes to implementing this method of mycotoxin mitigation since these fungi are living organisms that have been adapting, evolving and surviving on this planet for tens-of-millions of years. This document will serve as a critical review of the literature regarding pre-harvest A. flavus biocontrol and will discuss opportunities for improvements.
... Since mycotoxins are not easily deactivated or detoxified, the best control method recommended is to prevent fungi continued production. Biological agents such as fungus Clonostachys rosea strain IK726 and some aflatoxigenic Aspergillus flavus have successfully prevented Zearalenone and Deoxynivalenol production by Fusarium graminearum and F. culmorum, while the nonaflatoxigenic A. flavus competitively reduce aflatoxinproducing strains and in so doing, reshapes the fungal community [52], [53], [54], [55]. Competitive exclusion of toxigenic moulds with non-toxigenic strains in the field have been adopted in the United State of America, Nigeria, and Kenya [56], [57], [58], [59]. ...
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Abstract— Food shortage and contamination of the little available had been a challenge facing the African continent for centuries. Mycotoxins produced by fungi on agricultural produce all over the world are poisonous compounds, and these metabolites are stable under most food processing stages, and responsible for reduced food quality and value in addition to causing mycotoxicosis and other health conditions in man and animals, while the farmer loses huge profit due to rejected produce. It is generally accepted that the best way to eliminate the problems caused by mycotoxins is to engage in an effective prevention technique, while other methods such as detoxification and deactivation of already contaminated agricultural goods is another route that must be charted so as to be able to halt fungal infections and the resulting mycotoxicoses from the consumption contaminated feed, crops, and food products by animals a nd man. The use of high technique molecular equipment though ensures dependable results but are not readily accessible in quantifying the resulting outcomes in the African continent. The review is to raise the need for concerted effort at mitigating the losses and wastages resulting from fungal contamination
The antagonistic activity of Bacillus subtilis strain G1 was tested against various isolates of Aspergillus flavus in vitro. A talc-based powder formulation of B. subtilis strain G1 was prepared and evaluated to control A. flavus infection and aflatoxin B1 contamination in groundnut under greenhouse and field conditions. The results showed that B. subtilis strain G1 could inhibit the growth of all isolates of A. flavus tested in dual culture assay and the growth inhibition ranged from 93 to 100%. Results of greenhouse and field experiments indicated that B. subtilis strain G1 when applied to groundnut as seed treatment and soil application significantly suppressed A. flavus population in the soil, A. flavus infection and aflatoxin B1 content in kernels and increased the pod yield. These studies show that B. subtilis strain G1 has potential as a biocontrol agent for control of aflatoxin contamination in groundnut.
Article
Application of atoxigenic strains to compete against toxigenic strains of Aspergillus flavus strains has emerged as one of the practical strategies for reducing aflatoxin contamination in corn, peanut, and tree nuts. The actual mechanism that results in aflatoxin reduction is not fully understood. Real-time RT-PCR and relative quantification of gene expression protocol were applied to elucidate the molecular mechanism. Transcriptional analyses of aflatoxin biosynthetic gene cluster in dual culture of toxigenic and atoxigenic A. flavus strains were carried out. Six targeted genes, aflR, aflJ, omtA, ordA, pksA, and vbs, were downregulated to variable levels depending on paired strains of toxigenic and atoxigenic A. flavus. Consistent with the decreased gene expression levels, the aflatoxin concentrations in dual cultures were reduced significantly in comparison with toxigenic cultures. Fluorescent images showed fungal hyphae in dual culture displayed green fluorescent, and contacts of live hyphae were seen. A coconut agar plate assay was used to show that toxigenic A. flavus colony produced blue fluorescence under long UV exposure, suggesting that aflatoxin is exported outside fungal hyphae. Furthermore, the assay was applied to demonstrate the potential role of thigmo-regulation in fungal interaction.
Article
Single nucleotide polymorphisms (SNPs) of genome sequences of eight Aspergillus flavus and seven Aspergillus oryzae strains were extracted with Mauve, a multiple‐genome alignment program. A phylogenetic analysis with sequences comprised of concatenated total SNPs by the unweighted pair group method with arithmetic mean (UPGMA) of MAFFT adequately separated them into three groups, A. flavus S‐morphotype, A. flavus L‐morphotype, and A. oryzae. Divergence time inferred for A. flavus NRRL21882, the active agent of the biocontrol product Afla‐Guard®, and S‐morphotype was about 5.1 mya. Another biocontrol strain, A. flavus AF36, diverged from aflatoxigenic L‐morphotype about 2.6 to 3.0 mya. Despite the close relatedness of A. oryzae to A. flavus, A. oryzae strains likely evolved from aflatoxigenic Aspergillus aflatoxiformans (=A. parvisclerotigenus). A survey of A. flavus populations implies that prior Afla‐Guard® applications are associated with prevalence of NRRL21882‐type isolates in Mississippi fields. In addition, a few NRRL21882 relatives were identified. A. flavus Og0222, a biocontrol ingredient of Aflasafe™, was verified as a NRRL21882‐type strain, having identical sequence breakpoints that led to deletion of aflatoxin and cyclopiazonic acid gene clusters. A similar UPGMA analysis suggests that the occurrence of NRRL21882‐type strains is a more recent event.
Article
Aflatoxin contamination of peanuts is one of the most concerns in peanut production in China. Applying non-aflatoxigenic Aspergillus flavus strains, based on competitive exclusion, has been proved to be a promising strategy to reduce aflatoxin contamination in pre-harvest peanuts. Two non-aflatoxigenic A. flavus strains collected in China, which have been proved effectively reducing aflatoxin in the laboratory, were mixed with high aflatoxin producer to the soil in peanut growing season. The two non-aflatoxigenic strains significantly (P < 0.05) reduced aflatoxin contamination in peanut kernels under both normal and drought stress conditions in two fields. Compared to the control, the total aflatoxin (sum of aflatoxin B1 and B2) was reduced 26.7% to 99.12% in field 1, and 84.96% to 99.33% in field 2. The aflatoxin was reduced 84.96% to 99.33% under drought stress condition in two fields. The present study indicated the non-aflatoxigenic A. flavus strains could be potential biocontrol agents for reducing aflatoxin contamination under field condition.
Article
Aims: To use genome-wide single nucleotide polymorphisms (total SNPs) to develop a molecular method for distinguishing Aspergillus flavus and Aspergillus oryzae. Methods and results: Thirteen A. flavus and eleven A. oryzae genome sequences were obtained from the National Center for Biotechnology Information. These sequences were analysed by Mauve, a multiple-genome alignment program, to extract total SNPs between isolates of A. flavus, A. oryzae, or the two species. Averages of total SNPs of A. flavus isolates belonging to the same sclerotial morphotype (L-type = 178 952 ± 14 033; S-type = 133 188 ± 16 430) and A. oryzae isolates (152 336 ± 49 124) were consistently lower than those between the morphotypes and between the two species. Averages of total SNPs for L-type vs S-type (300 116 ± 1562) and S-type A. flavus vs A. oryzae (301 797 ± 4123) were similar but were 36% greater than that of L-type A. flavus vs A. oryzae (226 240 ± 10 779). Based on the devised criterion, ATCC 12892, Aspergillus oryzae (Ahlburg) Cohn, which had an averaged total SNPs 10-fold greater than that of other A. oryzae isolates, was determined to be close to Aspergillus parasiticus. Atoxigenic A. flavus field isolates, WRRL1519 and NRRL35739, were shown to more closely resemble A. oryzae than toxigenic L-type A. flavus. Biocontrol strains AF36 and K49 were genetically close to toxigenic L-type A. flavus. NRRL21882, the active agent of the commercialized biocontrol product Afla-Guard® GR, was genetically distant from all other A. flavus isolates. Conclusions: The close genetic relatedness between A. flavus and A. oryzae was confirmed and the evolutionary origins of atoxigenic A. flavus biocontrol strains were revealed. Significance and impact of the study: The study provides a greater understanding of genome similarity and dissimilarity between A. flavus and A. oryzae. The method can be an auxiliary technique for identifying A. flavus, A. oryzae.
Article
Aflatoxins in maize and peanuts remain a major cause of liver cancer and other human and animal health issues. The principal causal fungi are Aspergillus flavus and A. parasiticus. Relatively little attention has been paid to reducing aflatoxin formation before harvest. The most promising approach is biocontrol by competitive exclusion. This project aimed to demonstrate the efficacy of locally isolated strains of A. flavus for biocontrol of aflatoxin in maize in Thailand. After a rigorous process utilising molecular methods was used to select nontoxigenic A. flavus strains, field inoculum was produced by using hulled rice coated with A. flavus spores in molasses. Field experiments were conducted over two years in two districts, one of light sandy soil (Chokchai), the other a heavy, close textured, soil (Pakchong). Post harvest treatments representative of local practice were also undertaken. Crops 1 and 2 were not significantly contaminated with aflatoxin at the time of harvest, so any impact of biocontrol could not be assessed. However, wet shelling plus storage before drying resulted in increased aflatoxin contamination; biocontrol had no impact on this increase. In crops 3 and 4, biocontrol had a beneficial impact in some freshly harvested maize. Biocontrol treatments also significantly reduced aflatoxin contamination in samples from some treatments stored for two or four days after shelling, but had minimal effect in others. These experiments demonstrated that biocontrol can be highly effective in reducing aflatoxin contamination in maize in Thailand, both at harvest and during poor postharvest crop handling. However, results were inconsistent.
Chapter
Aflatoxins are secondary metabolites produced by the fungal genus Aspergillus (mainly A. flavus and A. parasiticus) that contaminate various agricultural commodities, but most prevalent in maize, groundnut, and cotton. Considered to be potent carcinogens and teratogens to humans and farm animals, aflatoxin contamination gets accentuated by hot and dry weather conditions, insect feeding and mechanical damage during and after harvest, and improper storage conditions. Growing global concerns about aflatoxin contamination have prompted search for effective control measures and specific regulations to limit exposure to these mycotoxins. Cultural practices include use of resistant varieties; control of insect pests, timely harvesting, proper drying, storage, sorting, and cleaning of harvested produce curtail aflatoxin contamination to some extent, and biological control strategies such as use of atoxigenic A. flavus strains have proven efficient in preventing infection by aflatoxin-producing strains. Genetic engineering for aflatoxin resistance through gene overexpression and recent development in area of transgenics through host-induced gene silencing of aflatoxin biosynthesis pathway genes have provided promising results in several crops such as cotton, corn, and groundnut. This book’s chapter provides comprehensive overview on the various strategies and also updates the status of research to achieve aflatoxin resistance in crop plants. The role of various factors affecting aflatoxin contamination is also discussed that help to take appropriate measures for successful control of aflatoxin resistance. The availability of advanced molecular techniques, cutting edge tools and technologies provides greater potential to the development of markers and QTLs for aflatoxin resistance speeding up the development of durable aflatoxin-resistant varieties.
Article
Aflatoxin contamination has a major economic impact on crop production in southern USA. Reduction of aflatoxin contamination in harvested crops has been achieved by applying non-aflatoxigenic biocontrol Aspergillus flavus strains that can out-compete wild aflatoxigenic A. flavus, reducing their numbers at the site of application. Currently, the standard method for applying biocontrol A. flavus strains to soil is using a nutrient-supplying carrier (e.g., pearled barley for Afla-Guard®). Granules of bioplastic (partially acetylated corn starch) have been investigated as an alternative nutritive carrier for biocontrol agents. Bioplastic granules have also been used to prepare a sprayable biocontrol formulation that gives effective reduction of aflatoxin contamination in harvested corn kernels with application of much smaller amounts to leaves later in the growing season. The ultimate goal of biocontrol research is to produce biocontrol systems that can be applied to crops only when long-range weather forecasting indicates they will be needed.
Article
A collection of 500 Aspergillus flavus isolates from four sesame varieties (S-34, S-35, S-38, and S-39) that were planted in field plots in the Mississippi Delta and in the Florida Panhandle were investigated because of low-level aflatoxin contamination detected in sesame seeds. A rapid molecular fingerprinting method was developed to assess the influence of prior applications of the atoxigenic Afla-Guard® biocontrol product whose active strain is NRRL21882 on the A. flavus populations within each field plot. Depending on sesame seed sampled, 66.7% to 95.9% of A. flavus isolates from Mississippi belonged to the NRRL21882 genotype, which lacks the aflatoxin and cyclopiazonic acid biosynthesis gene clusters. In contrast, only 5.0% to 32.5% of the isolates from Florida had lost both gene clusters. The high incidence of NRRL21882-like A. flavus in Mississippi sesame samples can be attributed to prior applications of Afla-Guard® in that local area. The results suggest the adaptability of this particular type of atoxigenic A. flavus biocontrol strain in the field.
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Aflatoxin contamination is caused by Aspergillus flavus and closely related fungi. In The Gambia, aflatoxin contamination of groundnut and maize, two staple and economically important crops, is common. Groundnut and maize consumers are chronically exposed to aflatoxins, sometimes at alarming levels, and this has severe consequences on their health and productivity. Aflatoxin contamination also impedes commercialization in local and international premium markets. In neighboring Senegal, an aflatoxin biocontrol product containing four atoxigenic isolates of A. flavus, Aflasafe SN01, has been registered and is approved for commercial use in groundnut and maize. We detected that the four genotypes composing Aflasafe SN01 are also native to The Gambia. The biocontrol product was tested during two years in 129 maize and groundnut fields and compared with corresponding untreated fields cropped by smallholder farmers in The Gambia. Treated crops contained up to 100% less aflatoxins than untreated crops. A large portion of the crops could have been commercialized in premium markets due to the low aflatoxin content (in many cases no detectable aflatoxins), both at harvest and after storage. Substantial aflatoxin reductions were also achieved when commercially produced groundnut received treatment. Here we report for the first time the use and effectiveness of an aflatoxin biocontrol product registered for use in two nations. With the current scale-out and -up efforts of Aflasafe SN01, a large number of farmers, consumers, and traders in The Gambia and Senegal will obtain health, income, and trade benefits. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .
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Aspergillus flavus has received a considerable amount of attention due to its ability to produce aflatoxin, a secondary metabolite that is both immunosuppressive and carcinogenic to animals and humans. Research on aflatoxin over the last 40 years has made it one of the best studied fungal secondary metabolites. In spite of the large volume of research in this area, many unanswered questions remain concerning the genetic regulation of aflatoxin production and the molecular signals that intimately associate the synthesis of aflatoxin with specific environmental and nutritional conditions. It is anticipated that the tools now available in the field of genomics will build upon our existing knowledge and provide answers to some of these questions. Complete genome sequences are now available for a number of fungal species that are closely related to A. flavus. This information can be used along with current genomic analyses in A. flavus to more closely examine the biosynthesis and regulation of secondary metabolism. The intent of this review is to summarize the large body of knowledge that exists from many years of research on A. flavus, with the hope that this information in the light of new genomic studies may bring scientists closer to unraveling the web of regulatory circuits that govern aflatoxin biosynthesis. Specifically, scientific findings in the following areas will be presented: classification and phylogenetic analyses of A. flavus, population biology, ecology and pathogenicity in agricultural environments , classical genetics including linkage group and mutant analyses, gene clusters, regulation of aflatoxin biosynthesis, and genomics.
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A new pasta-like (“Pesta”) process has been developed whereby fungal propagules are encapsulated (entrapped) in a wheat gluten matrix. A dough prepared from wheat flour, filler, fungus, and water was rolled into a thin sheet, air-dried, and ground into granules. The mycoherbicide agents Alternaria cassiae, A. crassa, Colletotrichum truncatum, and Fusarium lateritium were each formulated in Pesta and bioassayed against the target weed sicklepod, jimsonweed, hemp sesbania, or velvetleaf, respectively. The fungi grew and sporulated on the granules after application to soil. C. truncatum produced acervuli with conidia which were embedded in a protective mucilaginous exudate. In the greenhouse, 0.6- to 1.40-mm granules (14–18 and 18–30 mesh) containing the two Alternaria species or the Colletotrichum caused higher levels of weed mortality (68–100%) than did smaller granules (25–40%). When the granules contained F. lateritium, weed mortality was ≤30% regardless of granule size. The Pesta process appears to be a simple and effective way to formulate and deliver mycoherbicide agents.
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A three-year study was conducted to evaluate the use of a nonaflatoxin-producing strain of Aspergillus parasiticus (NRRL 13539) as a biocompetitive agent for the control of preharvest aflatoxin contamination of peanuts. The agent was added to the soil of the environmental control plot facility at the National Peanut Research Laboratory and tested by subjecting peanuts to optimal conditions for the development of aflatoxin contamination. Edible peanuts from the treated soil contained aflatoxin concentrations of 11, 1, and 40 ppb for crop years 1987, 1988, and 1989, respectively, compared to untreated peanuts with 531, 96, and 241 ppb, respectively. In addition, treatment in 1989 with low and high inoculum levels of a UV-induced mutant from the NRRL 13539 strain resulted in aflatoxin concentrations of 29 and 17 ppb, respectively, in edible peanuts. Soil populations of the biocompetitive agents were not higher than populations of wild strains of A. flavus/parasiticus in untreated soil subjected to late-seaso...
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A NEW disease, called 'turkey X disease' has been described since the widespread outbreaks of deaths in turkey poults in 19601. Post-mortem examination of dead poults from field outbreaks revealed acute hepatic necrosis, associated with generalized bile duct proliferation. Siller and Ostler2 directed attention to the similarities of the lesions to those of Senecio-alkaloid poisoning in the fowl described by Campbell3.
Article
A 3-yr field study was conducted to determine the effect of biological control formulations of nontoxigenic strains of Aspergillus flavus and A. parasiticus, peanut cultivars, and fungicides on preharvest aflatoxin contamination of peanuts. Formulation treatments consisted of (a) no biocontrol treatment, (b) the fungi cultured on rice via solid-state fermentation, (c) conidia of the fungi coated onto the surface of rice, and (d) conidia coated onto the surface of wheat (year one) or hulled barley (years two and three). Experiments consisted of factorial combinations of the four formulation treatments, two peanut cultivars (Florunner or Georgia Green), and two fungicide treatments (chlorothalonil or combinations of chlorothalonil and tebuconazole). Florunner and Georgia Green peanuts were each planted in 32 individual plots consisting of six rows 15.2 m in length. Biological control formulations, consisting of a mixture of nontoxigenic strains of A. flavus (NRRL 21882) and A. parasiticus (NRRL 21369), were applied to the same plots in each of the 3 yr at a rate of 56 kg/ha. Foliar applications of fungicides were made as recommended for control of leaf spot, with one treatment being full-season applications of chlorothalonil, and the other being two applications of chlorothalonil followed by four applications of tebuconazole and remaining applications of chlorothalonil. Only in year two of the study was late-season drought sufficient to produce preharvest aflatoxin contamination. All biocontrol formulation treatments produced significant reductions in aflatoxin compared with untreated controls, averaging 81%. There was also a significant cultivar effect on aflatoxin with Georgia Green averaging 119 μg/kg compared with 402 μg/kg for Florunner. No differences were observed between the two fungicide treatments, and there was no interaction among the three factors. Analysis of soil for populations of A. flavus and A. parasiticus throughout the study showed that all formulations, except the conidia-coated wheat in the first year, were effective in delivering competitive levels of the nontoxigenic strains. In the third year, which did not result in significant aflatoxin contamination, analysis of peanuts for fungal colonization showed no significant differences among biocontrol treatments (including control) for total amounts of A. flavus and A. parasiticus in peanuts. However, the incidence of toxigenic isolates in peanuts was significantly reduced by all three biocontrol formulations.
Article
Farmers stock peanuts from the same field dried to either 8 or 10% seed moisture content were stored for 6 months (October through March) in mechanically and naturally ventilated miniature metal warehouses. The initial temperatures for the 8% moisture content peanuts were 2–3 C higher than those for the 10% moisture content peanuts. This differential was maintained until early February. Relative humidities, 10 percentage points higher in the 10% initial moisture content peanuts began to equilibrate in December and were similar by late January. Final moisture content of the peanuts from the two mechanically ventilated warehouses was about 7% compared to 7.5% in the two naturally ventilated warehouses. Only small changes in total carbonyls and free fatty acids occurred during storage in the warehouses and sensory evaluation after storage indicated no significant differences among treatments within the medium and No. 1 sizes. No aflatoxin was detected in any seed size category before or after storage. Results indicated that quality of farmers stock peanuts, initial moisture content at 10% or less, can be maintained when stored in a properly constructed and operated mechanically or naturally ventilated warehouse.
Article
A biopesticide, afla-guard(®), has been developed for controlling aflatoxin contamination in peanuts. This product provides the means of introducing a competitive, non-aflatoxigenic strain ofAspergillus flavus into soils where peanuts are being grown. The introduced strain competitively excludes toxigenic strains naturally present from invading developing peanuts. The biocontrol technology was made commercially available in 2004 by Circle One Global, Inc., upon receiving U.S. Environmental Protection Agency section 3 registration of afla-guard(®) as a biopesticide. The product was applied to approximately 2000 ha of peanuts in Georgia and Alabama during the 2004 crop year. Application of afla-guard(®) changed the composition ofA. flavus soil populations from an average 71.1% toxigenic strains in untreated fields to only 4.0% in treated soils. Analyses of farmer's stock peanuts being delivered at seven different locations showed a consistent reduction in aflatoxin contamination in peanuts from fields treated with afla-guard(®). Over all locations, aflatoxin averaged 78.9 ng/g in untreated peanuts compared with 11.7 ng/g in treated peanuts, an 85.2% reduction. Peanuts from treated and untreated fields were stored together in separate warehouse bins at two different locations. Aflatoxin analyses at the Unadilla, GA location showed that 48.4% of shelled edible lots from untreated fields contained unacceptable levels of aflatoxin (>15 ng/g). At the Dawson, GA location, 15.8% of shelled lots from untreated fields contained >15 ng/g. At both locations, no shelled edible lots from treated fields contained >15 ng/g. Mean aflatoxin concentrations in edible peanuts from untreated and treated fields at Unadilla were 36.2 and 0.9 ng/g, respectively. At Dawson the respective means were 7.2 and 2.2 ng/g.
Article
Bacillus thuringiensis Berliner was encapsulated within a starch matrix and assayed for biological activity against neonate and second-instar larvae of the European corn borer, Ostrinia nubilalis (Hübner). When larvae ingested encapsulated B. thuringiensis, they digested the starch matrix and released into their guts B. thuringiensis crystals and spores, which initiated infection. Nearly 100% mortality occurred at all dosages and concentrations tested whenever the starch granules were hydrated and high relative humidity conditions (>80%) were maintained during the 24-h exposure period of the assay. Encapsulated B. thuringiensis stored in the laboratory for 4 mo exhibited no detectable decrease in pathological activity.
Article
LARGE numbers of turkey poults1 and ducklings2 died on British farms in 1960 as a result of consuming groundnut (Arachis hypogaea) meal imported from Brazil. Afterwards, outbreaks of disease associated with the feeding of Brazilian groundnut meal were reported in cattle3, pigs4, and sheep (Buxton, J. C., personal communication). More recently it has been shown that some samples of groundnut products from a number of other producing countries are toxic to animals5.
Article
‘Pesta’ granules in which fungal propagules are encapsulated in a wheat gluten matrix were prepared in multipound quantities by twin-screw extrusion and fluid bed drying. Dough formulations for extrusion contained wheat flour and kaolin, or wheat flour, kaolin and rice flour, plus water and fungal inoculum. Conidial inoculum of Colletotrichum truncatum, a pathogen of the weed hemp sesbania (Sesbania exaltata), survived laboratory scale dough preparation [100% retention of colony-forming units (c.f.u.)] better than dough preparation for twin-screw extrusion (8‐10% c.f.u. retention). The loss in viability was linked to the lower water content of dough used in the twin-screw extruder. Fluid bed drying reduced viability further to 1%. Retention of viability after twin-screw extrusion and fluid bed drying at 35‐50 ∞C was 35% with Alternaria conjuncta/infectoria, a pathogen of swamp dodder (Cuscuta gronovii). Retention was 86‐100% with atoxigenic strains of Aspergillus flavus and Aspergillus parasiticus used as biocompetitors to reduce aflatoxin levels in peanuts. In the greenhouse, twin-screw-extruded granules containing C. truncatum (at about 5 · 10 4 c.f.u. g )1 ) caused high levels of infection and mortality in hemp sesbania seedlings.
Article
Experiments were conducted to determine the potential for biological control of aflatoxin contamination of peanuts during storage. Florunner peanuts were treated in field plots by applying competitive, nontoxigenic strains of Aspergillus flavus and A. parasiticus, at 76 and 67 days after planting in 1998 and 1999, respectively. After harvest, half the peanuts from both treated and control plots were sprayed with an aqueous conidial suspension containing the nontoxigenic strains; the other half of the peanuts from each group were not sprayed. The peanuts were then placed in separate compartments of a miniature warehouse. Therefore, storage treatments consisted of peanuts that were (1) not treated at all; (2) treated prior to storage only; (3) field-treated only; (4) treated both in the field and prior to storage. Peanuts were stored for 3–5 months under high temperature and relative humidity conditions designed to promote aflatoxin contamination. In 1998, peanuts were not contaminated with aflatoxins prior to storage. After storage, peanuts that were never treated with the competitive fungi contained an average of 78.0 ppb of aflatoxins. Peanuts not treated in the field but receiving the spray treatment before storage contained 48.8 ppb. Peanuts treated in the field only averaged 1.4 ppb, and peanuts treated both in the field and prior to storage contained 0.8 ppb. In 1999, peanuts suffered from late-season drought and were contaminated with aflatoxins at harvest, with controls averaging 516.8 ppb compared with 54.1 ppb in treated peanuts. After storage, non-field-treated peanuts averaged 9145.1 ppb compared with 374.2 ppb for peanuts that had been field-treated, a 95.9% reduction. Spraying of pods with the nontoxigenic strains postharvest but prior to storage provided no additional protection against aflatoxin contamination. Results demonstrated that field application of the nontoxigenic strains had a carry-over effect and reduced aflatoxin contamination that occurred in storage.
Article
Studies were conducted during 1994 and 1995 in the environmental control plot facility at the National Peanut Research Laboratory to determine the effect of different inoculum rates of biological control agents on preharvest aflatoxin contamination of Florunner peanuts. Biocontrol agents were nontoxigenic color mutants ofAspergillus flavusandAspergillus parasiticusthat were grown on rice for use as soil inoculum. Three replicate plots (4.0 × 5.5 m) were treated with 0, 2, 10, and 50 g/m of row (0, 20, 100, and 500 lb/acre, respectively) of an equal mixture of the color mutant-infested rice in 1994, and the same plots were retreated in 1995. Aflatoxin concentrations were determined by high performance liquid chromatographic analysis of all peanuts. Treatment means for total kernels in 1994 were 337.6, 73.7, 34.8, and 33.3 ppb for the 0, 2, 10, and 50 g/m treatments, respectively. Regression analysis indicated a trend toward lower aflatoxin concentrations with increasing rates of inoculum (R2= 0.40;P< 0.05). For the same repeated treatments in 1995 aflatoxin concentrations in total kernels averaged 718.3, 184.4, 35.9, and 0.4 ppb. Regression analysis revealed a stronger relationship between inoculum rate and aflatoxin concentrations (R2= 0.66;P< 0.05) in the second year of treatment. Compared with untreated controls, the 2, 10, and 50 g/m treatments produced respective reductions in aflatoxin of 74.3, 95.0, and 99.9% in the second year. The data indicated not only a treatment-related effect, but also that a higher degree of control might be achieved when plots or fields are retreated with biocontrol agents in subsequent years.
Article
A two-year study was conducted to evaluate the efficacy of three formulations of nontoxigenic strains of Aspergillus flavus and Aspergillus parasiticus to reduce preharvest aflatoxin contamination of peanuts. Formulations included: (1) solid-state fermented rice; (2) fungal conidia encapsulated in an extrusion product termed Pesta; (3) conidia encapsulated in pregelatinized corn flour granules. Formulations were applied to peanut plots in 1996 and reapplied to the same plots in 1997 in a randomized design with four replications, including untreated controls. Analysis of soils for A. flavus and A. parasiticus showed that a large soil population of the nontoxigenic strains resulted from all formulations. In the first year, the percentage of kernels infected by wild-type A. flavus and A. parasiticus was significantly reduced in plots treated with rice and corn flour granules, but it was reduced only in the rice-treated plots in year two. There were no significant differences in total infection of kernels by all strains of A. flavus and A. parasiticus in either year. Aflatoxin concentrations in peanuts were significantly reduced in year two by all formulation treatments with an average reduction of 92%. Reductions were also noted for all formulation treatments in year one (average 86%), but they were not statistically significant because of wide variation in the aflatoxin concentrations in the untreated controls. Each of the formulations tested, therefore, was effective in delivering competitive levels of nontoxigenic strains of A. flavus and A. parasiticus to soil and in reducing subsequent aflatoxin contamination of peanuts.
Article
A 2-year study was carried out to determine the effect of applying nontoxigenic strains of Aspergillus flavus and A. parasiticus to soil separately and in combination on preharvest aflatoxin contamination of peanuts. A naturally occurring, nontoxigenic strain of A. flavus and a UV-induced mutant of A. parasiticus were applied to peanut soils during the middle of each of two growing seasons using a formulation of conidia-coated hulled barley. In addition to an untreated control, treatments included soil inoculated with nontoxigenic A. flavus only, soil inoculated with nontoxigenic A. parasiticus only, and soil inoculated with a mixture of the two nontoxigenic strains. Plants were exposed to late-season drought conditions that were optimal for aflatoxin contamination. Results from year one showed that significant displacement (70%) of toxigenic A. flavus occurred only in peanuts from plots treated with nontoxigenic A. flavus alone; however, displacement did not result in a statistically significant reduction in the mean aflatoxin concentration in peanuts. In year two, soils were re-inoculated as in year one and all treatments resulted in significant reductions in aflatoxin, averaging 91.6%. Regression analyses showed strong correlations between the presence of nontoxigenic strains in peanuts and aflatoxin reduction. It is concluded that treatment with the nontoxigenic A. flavus strain alone is more effective than the A. parasiticus strain alone and equally as effective as the mixture.
Article
Granule carriers for insect control agents have been used for many years, especially for control of soil-borne pests. Granular baits have not been practical for foliar application because they do not stick well and are susceptible to removal by wind or rain. A simple and economic technique to prepare adherent granules has been developed. The granules are made of starch which, when applied to wet surfaces and allowed to dry, will adhere even in the presence of additional water. Granules were formulated by mixing pregelatinized starch with a water-organic solvent solution. Solvents tested included methanol, ethanol, n-butanol, 2-propanol, acetone, and 1,4-dioxane. The resulting mass, after drying, easily crumbled into particles that could then be sieved to desired particle sizes. Assays that measured resistance to wash-off demonstrated that granules made with 2-propanol were retained on both glass and cotton leaf surfaces, whereas granules made with water alone washed off easily. Granules made with 2-propanol and Bacillus thuringiensis Berliner showed no loss of insecticidal activity when compared with granules made with water alone. A field study testing adult Diabrotica virgifera virgifera LeConte attraction to traps baited with p-methoxycinnamaldehyde encapsulated within starch granules demonstrated a sustained rate of release of the attractant over a 12-d period. Possible benefits of an adherent pesticidal bait formulation are discussed.
Article
Formulations containing spores of non-toxigenic strains of fungi are useful biocontrol agents for preventing toxin contamination in agricultural commodities, especially those for human and animal consumption such as peanuts, corn and cotton. These formulations include spores mixed with vegetable oil and applied to dry grain. Diatomaceous earth is added to the spore, oil and grain mixture to form a flowable formulation.
Article
A comparison of the invasion of flowers, aerial pegs, and kernels by wild-type and mutant strains of Aspergillus flavus or A. parasiticus along with aflatoxin analyses of kernels from different drought treatments have supported the hypothesis that preharvest contamination with aflatoxin originates mainly from the soil. Evidence in support of soil invasion as opposed to aerial invasion was the following. A greater percentage of invasion of kernels rather than flower or aerial pegs by either wild-type A. flavus or mutants. Significant invasion by an A. parasiticus color mutant occurred only in peanuts from soil supplemented with the mutant, whereas adjacent plants in close proximity but in untreated soil were only invaded by wild-type A. flavus or A. parasiticus. Aflatoxin data from drought-stressed, visibly undamaged peanut kernels showed that samples from soil not supplemented with a mutant strain contained a preponderance of aflatoxin B's (from wild-type A. flavus) whereas adjacent samples from mutant-supplemented soil contained a preponderance of B's plus G's (from wild-type and mutant A. parasiticus). Preliminary data from two air samplings showed an absence of propagules of A. flavus or A. parasiticus in air around the experimental facility.
Article
Environmental control plots adjusted to late season drought and elevated soil temperatures were inoculated at peanut planting with low and high levels of conidia, sclerotia, and mycelium from a brown conidial mutant of Aspergillus parasiticus. Percentage infection of peanut seeds from undamaged pods was greatest for the subplot containing the high sclerotial inoculum (15/cm2 soil surface). Sclerotia did not germinate sporogenically and may have invaded seeds through mycelium. In contrast, the mycelial inoculum (colonized peanut seed particles) released large numbers of conidia into soil. Soil conidial populations of brown A. parasiticus from treatments with conidia and mycelium were positively correlated with the incidence of seed infection in undamaged pods. The ratio of A. flavus to wild-type A. parasiticus in soil shifted from 7:3 to 1:1 in the uninoculated subplot after instigation of drought, whereas in all subplots treated with brown A. parasiticus, the ratio of the two species became approximately 8:2. Despite high levels of brown A. parasiticus populations in soil, native A. flavus often dominated peanut seeds, suggesting that it is a more aggressive species. Sclerotia of wild-type A. parasiticus formed infrequently on preharvest peanut seeds from insect-damaged pods.
The Toxicology of Aflatoxins
  • D L Eaton
  • J D Groopman
Eaton, D.L. and J.D. Groopman. 1994. The Toxicology of Aflatoxins. Academic Press, San Diego, CA.
Environmental control plot facility with manipulable soil temperature
  • P D Blankenship
  • R J Cole
  • T H Sanders
  • R A Hill
Blankenship, P.D., R.J. Cole, T.H. Sanders, and R.A. Hill. 1983. Environmental control plot facility with manipulable soil temperature. Oleagineux 38:615-620.