Article

Development of Biocontrol Technology to Manage Aflatoxin Contamination in Peanuts

January 2009
Peanut Science 36(1)

Authors:

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.

Present Status and Perspective on the Future Use of Aflatoxin Biocontrol Products

Article

Full-text available

Apr 2020

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 Atoxigenic Biocontrol Product Aflasafe SN01 Is a Valuable Tool to Mitigate Aflatoxin Contamination of Both Maize and Groundnut Cultivated in Senegal

Article

Full-text available

Aug 2019
PLANT DIS

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 .

A Critical Review of Aflatoxin Contamination of Peanuts in Malawi and Zambia: The Past, Present, and Future

Article

Full-text available

Jun 2018
PLANT DIS

Samuel Muriu Njoroge

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.

Development and scale-up of bioprotectants to keep staple foods safe from aflatoxin contamination in Africa

Chapter

Full-text available

Nov 2021

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.

Effect of non-aflatoxigenic strains of Aspergillus flavus on aflatoxin contamination of pre-harvest peanuts in fields in China

Article

Full-text available

May 2021

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.

Aflatoxins: Producing-Molds, Structure, Health Issues and Incidence in Southeast Asian and Sub-Saharan African Countries

Article

Full-text available

Feb 2020
Int J Environ Res Publ Health

Noreddine Benkerroum

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.

Aflatoxins: Production, Structure, Health Issues and Incidence in Southeast Asian and Sub-Saharan African Countries

Preprint

Full-text available

Jan 2020

Noreddine Benkerroum

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.

Aflatoxins: A Comprehensive Overview

Preprint

Full-text available

Nov 2019

Noreddine Benkerroum

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.

Aflatoxin contamination of groundnut (Arachis hypogaea L.): Predisposing factors and management interventions

Article

Nov 2018
FOOD CONTROL

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.

Preventing mycotoxin contamination in groundnut cultivation

Chapter

Full-text available

Jan 2018

Seed Treatment with Trichoderma Harzianum Strain kd Formulation Reduced Aflatoxin Contamination in Groundnuts

Article

Feb 2015
J PLANT DIS PROTECT

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.

e-Book: Research Efforts, Challenges and Opportunities in Mitigating Aflatoxins in Food and Agricultural Crops and its Global Health Impacts

Book

Full-text available

Dec 2022

Aflatoxins are a group of polyketide mycotoxins that are produced during fungal development as secondary metabolites mainly by members of the Aspergillus section Flavi (Yu et al., 2004; Norlia et al., 2019; Uka et al., 2019). Contamination of food, feed and agricultural commodities by aflatoxins impose an enormous economic concern, as these chemicals are highly carcinogenic, they can directly influence the structure of DNA (Bbosa et al., 2013; Feng et al., 2016). They can lead to fetal maldevelopment and miscarriages, and are known to suppress immune systems (Ahmed Adam et al., 2017). In a global context, aflatoxin contamination is considered a perennial concern between the 35N and 35S latitude where developing countries are mainly situated. With the expansion of these boundaries, aflatoxins are increasingly becoming a problem in countries that previously did not have to worry about aflatoxin contamination. Given the continuing problems arising from aflatoxin contamination of food and agricultural commodities throughout the world, aflatoxins research is becoming one of the most exciting and rapidly developing areas of microbial toxins research. The applications include many disciplines, from medicine to agriculture. Nowadays, traditional research on aflatoxins has been expanded to modern technologies such as omics for understanding the regulation of aflatoxin biosynthetic pathway genes, the taxonomy, ecology, biochemistry, and evolution of aflatoxigenic fungi in addition to strategies to pre- and post-harvest management of aflatoxin contamination. This includes improving host resistance of susceptible crops such as cotton, maize, peanut, and tree nuts via genetic engineering. The present Research Topic includes one review article, one mini-review and fifteen original research articles. Contributors highlighted challenges and opportunities in mitigating aflatoxins in food and agricultural crops and the current knowledge on the global health issues of aflatoxins and aflatoxigenic fungi. All aspects of aflatoxin contamination of food and agricultural crops from epidemiology to ecology, biochemistry, molecular biology, biocontrol strategies, natural inhibitors of fungal growth and aflatoxin production, transgenic hosts and pre- and post-harvest management strategies have been discussed.

Application of Non-Aflatoxigenic Aspergillus flavus for the Biological Control of Aflatoxin Contamination in China

Article

Full-text available

Sep 2022

Biological control through the application of competitive non-aflatoxigenic Aspergillus flavus (A. flavus) to the soil during peanut growth is a practical method for controlling aflatoxin contamination. However, appropriate materials need to be found to reduce the cost of biocontrol products. In this study, a two-year experiment was conducted under field conditions in China, using a native non-aflatoxigenic strain to explore its effect. After three months of storage under high humidity, aflatoxin levels remained low in peanuts from fields treated with the biocontrol agent. Three types of substrates were tested with the biocontrol agent: rice grains, peanut meal (peanut meal fertilizer) and peanut coating. Compared to untreated fields, these formulations resulted in reductions of 78.23%, 67.54% and 38.48%, respectively. Furthermore, the ratios of non-aflatoxigenic A. flavus recovered in the soils at harvest in the treated fields were between 41.11% and 96.67% higher than that in untreated fields (25.00%), indicating that the rice inoculum was the most effective, followed by the peanut meal fertilizer and peanut coating. In 2019, the mean aflatoxin content of freshly harvested peanuts in untreated fields was 19.35 µg/kg higher than that in the fields treated with 7.5 kg/ha rice inoculum, which was 1.37 µg/kg. Moreover, no aflatoxin was detected in the two other plots treated with 10 and 15 kg/ha rice inoculum. This study showed that the native Chinese non-aflatoxigenic strain of A. flavus (18PAsp-zy1) had the potential to reduce aflatoxin contamination in peanuts. In addition, peanut meal can be used as an alternative substrate to replace traditional grains, reducing the cost of biocontrol products.

Mycotoxins; a burden in Africa

Article

Full-text available

Mar 2020

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

Genetic fingerprinting and aflatoxin production of Aspergillus section Flavi associated with groundnut in eastern Ethiopia

Article

Full-text available

Aug 2021
BMC MICROBIOL

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.

Benefits to Plant Health and Productivity From Enhancing Plant Microbial Symbionts

Article

Full-text available

Apr 2021

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.

Practical considerations will ensure the continued success of pre-harvest biocontrol using non-aflatoxigenic Aspergillus flavus strains

Article

Full-text available

Jan 2021

Geromy G Moore

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.

Functional Biology and Molecular Mechanisms of Host-Pathogen Interactions for Aflatoxin Contamination in Groundnut (Arachis hypogaea L.) and Maize (Zea mays L.)

Article

Full-text available

Mar 2020

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.

Functional Biology and Molecular Mechanisms of Host-Pathogen Interactions for Aflatoxin Contamination in Groundnut (Arachis hypogaea L.) and Maize (Zea mays L.)

Article

Full-text available

Mar 2020

Thermosensitive Hydrogel for Encapsulation and Controlled Release of Biocontrol Agents to Prevent Peanut Aflatoxin Contamination

Article

Full-text available

Mar 2020

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.

Functional Biology and Molecular Mechanisms of Host-Pathogen Interactions for Aflatoxin Contamination in Groundnut (Arachis hypogaea L.) and Maize (Zea mays L.)

Article

Full-text available

Mar 2020

“Ground-Truthing” Efficacy of Biological Control for Aflatoxin Mitigation in Farmers’ Fields in Nigeria: From Field Trials to Commercial Usage, a 10-Year Study

Article

Full-text available

Nov 2019

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.

Mitigating Aflatoxin Contamination in Groundnut through A Combination of Genetic Resistance and Post-Harvest Management Practices

Article

Full-text available

Jun 2019

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.

Mitigating Aflatoxin Contamination in Groundnut through A Combination of Genetic Resistance and Post-Harvest Management Practices

Article

Full-text available

Jun 2019

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.

Biological Control of Aflatoxigenic Fungi on Peanut for the Pre-Harvest Approach

Article

Full-text available

Jun 2019

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.

Cultural and Genetic Approaches to Manage Aflatoxin Contamination: Recent Insights Provide Opportunities for Improved Control

Article

Jun 2018
PHYTOPATHOLOGY

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.

Aflatoxins: biosynthesis, prevention and eradication

Article

Full-text available

Oct 2017

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.

MOLECULAR DETECTION THE INFLUENCE OF AFLATOXIN BIOSYNTHETIC GENES BY ASPERGILLUS FLAVUS BEFORE AND AFTER BACILLUS SUBTLIS AND CANDIDA ALBICANS BIOCONTROL

Conference Paper

Full-text available

Jan 2017

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

MOLECULAR DETECTION THE INFLUENCE OF AFLATOXIN BIOSYNTHETIC GENES BY ASPERGILLUS FLAVUS BEFORE AND AFTER BACILLUS SUBTLIS AND CANDIDA ALBICANS BIOCONTROL

Article

Full-text available

Oct 2017

Controlling aflatoxins in maize in Africa: strategies, challenges and opportunities for improvement

Chapter

Jul 2017

Aflatoxins: A Global Concern for Food Safety, Human Health and Their Management

Article

Full-text available

Nov 2016

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.

Pre-harvest silk treatment with Trichoderma harzianum reduces aflatoxin contamination in sweetcorn

Article

Aug 2016

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.

Mitigation of aflatoxin contamination in Nigerian maize with atoxigenic strain mixtures

Article

Jun 2010
PHYTOPATHOLOGY

Environmental distribution and genetic diversity of vegetative compatibility groups determine biocontrol strategies to mitigate aflatoxin contamination of maize by Aspergillus flavus

Article

Full-text available

Oct 2015

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.

Suppression of Aflatoxin Biosynthesis in Aspergillus flavus by 2-Phenylethanol Is Associated with Stimulated Growth and Decreased Degradation of Branched-Chain Amino Acids

Article

Full-text available

Sep 2015

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.

Aflatoxin biocontrol in practice requires a multidisciplinary, long-term approach

Article

Full-text available

Feb 2023

One of the most elusive food safety problems is the contamination of staple crops with the highly carcinogenic aflatoxins produced by Aspergillus section Flavi fungi. Governments, farmers, institutions, consumers, and companies demand aflatoxin solutions. Many aflatoxin management technologies exist, but their real-life use and effectiveness is determined by diverse factors. Biocontrol products based on atoxigenic isolates of A. flavus can effectively reduce aflatoxins from field to fork. However, development, testing, and registration of this technology is a laborious process. Further, several barriers prevent the sustainable use of biocontrol products. There are challenges to have the products accepted, to make them available at scale and develop mechanisms for farmers to buy them, to have the products correctly used, to demonstrate their value, and to link farmers to buyers of aflatoxin-safe crops. Developing an effective aflatoxin management technology is the first, major step. The second one, perhaps more complicated and unfortunately seldomly discussed, is to develop mechanisms to have it used at scale, sustainably, and converged with other complementary technologies. Here, challenges and actions to scale the aflatoxin biocontrol technology in several countries in sub-Saharan Africa are described with a view to facilitating aflatoxin management efforts in Africa and beyond.

Impact of frequency of application on the long-term efficacy of the biocontrol product Aflasafe in reducing aflatoxin contamination in maize

Article

Full-text available

Nov 2022

Aflatoxins, produced by several Aspergillus section Flavi species in various crops, are a significant public health risk and a barrier to trade and development. In sub-Saharan Africa, maize and groundnut are particularly vulnerable to aflatoxin contamination. Aflasafe, a registered aflatoxin biocontrol product, utilizes atoxigenic A. flavus genotypes native to Nigeria to displace aflatoxin producers and mitigate aflatoxin contamination. Aflasafe was evaluated in farmers’ fields for 3 years, under various regimens, to quantify carry-over of the biocontrol active ingredient genotypes. Nine maize fields were each treated either continuously for 3 years, the first two successive years, in year 1 and year 3, or once during the first year. For each treated field, a nearby untreated field was monitored. Aflatoxins were quantified in grain at harvest and after simulated poor storage. Biocontrol efficacy and frequencies of the active ingredient genotypes decreased in the absence of annual treatment. Maize treated consecutively for 2 or 3 years had significantly (p < 0.05) less aflatoxin (92% less) in grain at harvest than untreated maize. Maize grain from treated fields subjected to simulated poor storage had significantly less (p < 0.05) aflatoxin than grain from untreated fields, regardless of application regimen. Active ingredients occurred at higher frequencies in soil and grain from treated fields than from untreated fields. The incidence of active ingredients recovered in soil was significantly correlated (r = 0.898; p < 0.001) with the incidence of active ingredients in grain, which in turn was also significantly correlated (r = −0.621, p = 0.02) with aflatoxin concentration. Although there were carry-over effects, caution should be taken when drawing recommendations about discontinuing biocontrol use. Cost–benefit analyses of single season and carry-over influences are needed to optimize use by communities of smallholder farmers in sub-Saharan Africa.

Pistachio Male Inflorescences as an Alternative Substrate for the Application of Atoxigenic Strains of Aspergillus flavus

Article

Nov 2022
PLANT DIS

Aflatoxins are carcinogens mainly produced by Aspergillus flavus and A. parasiticus in susceptible crops, including pistachio. The primary inoculum sources of these pathogens are plant debris in the orchard soils. In Californian fields, one approach to controlling aflatoxin contamination is based on releasing the atoxigenic strain of A. flavus AF36 in inoculated (coated) sorghum grains (AF36 Prevail ® ). However, this control method can fail due to poor sporulation of the AF36 strain or sorghum grain losses due to predation. In 2008 and 2018, we showed that toxigenic and atoxigenic isolates of Aspergillus spp. frequently colonized fallen inflorescences of male pistachios. Under controlled conditions, AF36 strain profusely colonized pistachio male inflorescences when humidity was higher than 90%. However, there were significant differences (between types of inflorescence (aerial > fallen). In 2016, we considerably (P = 0.015) increased the population of AF36 on the canopies of trees when fallen inflorescences were inoculated with AF36, compared to untreated trees. In 2017 and 2018, these differences were not detected (P > 0.05) due to cross-contamination of AF36 strain between seasons and neighboring plots. In any case, the density of AF36 spores on the canopy of the inflorescence-treated trees was similar (P > 0.05) to those of treated trees with the commercial product. Here, we present a new method for applying AF36 strain based on using a natural, abundant, and uniformly distributed substrate in pistachio fields, and we discuss how it can be improved. Furthermore, our results indicate that in pistachio orchards, where biocontrol practices are not conducted, eliminating this important source of toxigenic Aspergillus inoculum is recommended.

Antagonistic Effect of Biocontrol Agents on Aflatoxin producing Fungal Isolates from Contaminated Peanuts

Article

Sep 2022

Aflatoxins are the major and global concern in food and feed matrices. These fungi affect cereals, nuts and spices commodities during the pre and post harvesting treatments, handling and storage. The fungal isolates harbour within the crop or food material and lead to the production of toxin in these materials. Soil borne pathogenic fungi are responsible for significantly decreasing yield by affecting the crop. Aspergillus spp. is the prominent pathogen responsible for Aflatoxin contamination. Chemical control of this fungal pathogen may be harmful or can cause dangerous effects on consumers as well as on soil quality. However, the use of biological methods in controlling this plant pathogen is a beneficial technique for ecology and environment. So, these biocontrol agents are recommended as these are eco-friendly and reduce the growth of fungal pathogens and contaminants. Considering this in our current investigation, we have studied in vitro antagonistic activity of biocontrol agent- Trichoderma asperelloides against the aflatoxin producing fungi isolated from peanut. The study was carried out by performing the dual culture technique. Further the medium was also analysed for Aflatoxin content by using Ultra High-Performance Liquid Chromatography with Fluorescence Detection (UHPLC-FLD) technique.

Development of biochar-impregnated alginate beads for the delivery of biocontrol agents for peanut aflatoxin

Article

Jun 2022

The competitive inhibition of aflatoxigenic fungi by non-aflatoxigenic Aspergillus flavus has proved to be an effective method to prevent and control peanut aflatoxin contamination, and most of the currently used inoculum carriers are grains. In this study, the reliability and efficiency of replacing grain kernels with novel chitosan-coated alginate-poly(N-isopropylacrylamide) (PNIPAAm) beads impregnated with biochar (CSACB) were evaluated. Characterisation of the beads was performed by SEM, thermogravimetry analysis (TGA), and swelling properties analyses. The optimised CSACB beads had good physical stability, shelf life, and entrapment efficiency. In addition, the water-holding capacity and porous structure were excellent, as the biochar provided a beneficial microenvironment for the attachment and microbial growth of the biocontrol fungus. The effect of reducing aflatoxin in peanuts was verified experimentally. Collectively, the novel CSACB beads are suitable carriers of non-aflatoxigenic A. flavus for the biocontrol of peanut aflatoxin.

Aflasafe SN01 is the First Biocontrol Product Approved for Aflatoxin Mitigation in Two Nations, Senegal and The Gambia

Article

Full-text available

Dec 2020
PLANT DIS

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 .

Deciphering the origin of Aspergillus flavus NRRL21882, the active biocontrol agent of Afla‐Guard ®

Article

Nov 2020

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.

Quantification of the Aflatoxin Biocontrol Strain Aspergillus flavus AF36 in Soil and in Nuts and Leaves of Pistachio by Real-Time PCR

Article

Oct 2020
PLANT DIS

The species Aspergillus flavus and A. parasiticus are commonly found in the soils of nut-growing areas in California. Several isolates can produce aflatoxins that occasionally contaminate nut kernels conditioning their sale. The strain AF36 of A. flavus, which does not produce aflatoxins, is registered as a biocontrol agent for use in almond, pistachio, and fig crops in California. After application in the orchards, AF36 displaces aflatoxin-producing Aspergillus spp. and thus reduces aflatoxin contamination. Vegetative compatibility assays (VCA) have traditionally been used to track AF36 in soils and crops where it has been applied. However, VCA is labor-intensive and time-consuming. Here, we developed a quantitative real-time PCR (qPCR) protocol to quantify proportions of AF36 accurately and efficiently in different substrates. Specific primers to target AF36 and toxigenic strains of A. flavus and A. parasiticus were designed based on sequence of aflC, a gene essential for aflatoxin biosynthesis. Standard curves were generated to calculate proportions of AF36 based on threshold values (Cq). Verification assays using pure DNA and conidial suspension mixtures demonstrated a significant relationship by regression analysis between known and qPCR-measured AF36 proportions in DNA (R 2 = 0.974; P < 0.001) and conidia mixtures (R 2 = 0.950; P < 0.001). The tests conducted by qPCR in pistachio leaves, nuts, and soil samples demonstrated the usefulness of the qPCR method to precisely quantify proportions of AF36 in diverse substrates, ensuring important time and cost savings. The outputs of the current study will serve to design better aflatoxin management strategies for pistachio and other crops.

Prevalence of NRRL21882-like (Afla-Guard ® ) Aspergillus flavus on sesame seeds grown in research fields in the Mississippi Delta

Article

Jul 2020

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.

Biotechnological Strategies for Development of Aflatoxin-Free Crops

Chapter

Nov 2019

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.

Genome‐wide nucleotide variation distinguishes Aspergillus flavus from Aspergillus oryzae and helps to reveal origins of atoxigenic A. flavus biocontrol strains

Article

Aug 2019

Perng-Kuang Chang

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.

Dual culture of atoxigenic and toxigenic strains of Aspergillus flavus to gain insight into repression of aflatoxin biosynthesis and fungal interaction

Article

Jun 2019

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.

Biological Control of Aflatoxin Contamination in U.S. Crops and the Use of Bioplastic Formulations of Aspergillus flavus Biocontrol Strains To Optimize Application Strategies

Article

Apr 2017

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.

Biological control of pre-harvest aflatoxin contamination in groundnut ( Arachis hypogaea L.) with Bacillus subtilis G1

Article

Mar 2016

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.

The Diversity and Antagonistic Ability of Trichoderma spp. on the Aspergillus Flavus Pathogen on Peanuts in North Center of Vietnam

Article

Full-text available

Nov 2014

Use of a Biocompetitive Agent to Control Preharvest Aflatoxin in Drought Stressed Peanuts

Article

Full-text available

Nov 1992
J FOOD PROTECT

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...

Epidemiology of Aflatoxin Formation by Aspergillus Flavus*

Article

Full-text available

Nov 2003

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.

Formulation of Mycoherbicides Using a Pasta-like Process

Article

Full-text available

Dec 1991

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.

Toxicity associated with Certain Samples of Groundnuts

Article

Dec 1961

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.

Combined Effects of Biological Control Formulations, Cultivars, and Fungicides on Preharvest Colonization and Aflatoxin Contamination of Peanuts by Aspergillus Species

Article

Jul 2004

Joe W. Dorner

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.

Storability of Farmers Stock Peanuts at Two Moisture Levels in Mechanically and Naturally Ventilated Miniature Warehouses

Article

Jan 1989

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.

Development and commercial use of afla-Guard(®), an aflatoxin biocontrol agent

Article

Mar 2006

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.

Starch-Encapsulated Bacillus thuringiensis: A Potential New Method for Increasing Environmental Stability of Entomopathogens

Article

Feb 1988
ENVIRON ENTOMOL

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.

Toxicity associated with Certain Samples of Groundnuts

Article

Dec 1961

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.

Twin-screw extrusion of ‘Pesta’-encapsulated biocontrol agents

Article

Nov 1997

‘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.

Effect of application of nontoxigenic strains of Aspergillus flavus and A. parasiticus on subsequent aflatoxin contamination of peanuts in storage

Article

Dec 2002
J STORED PROD RES

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.

Effect of Inoculum Rate of Biological Control Agents on Preharvest Aflatoxin Contamination of Peanuts

Article

Jul 1998

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.

Evaluation of biological control formulations to reduce aflatoxin contamination in peanuts

Article

Mar 2003

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.

Separate and combined applications of nontoxigenic Aspergillus flavus and A. parasiticus for biocontrol of aflatoxin in peanuts

Article

Apr 2007

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.

Adherent Starch Granules for Encapsulation of Insect Control Agents

Article

Aug 1992
J ECON ENTOMOL

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.

Biological control formulations containing spores of nontoxigenic strains of fungi for toxin control of food crops.

Article

Jan 2001

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.

Color mutants of Aspergillus flavus and Aspergillus parasiticus in a study of preharvest invasion of peanuts

Article

Dec 1986

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.

Effect of Aspergillus parasiticus soil inoculum on invasion of peanut seeds

Article

Apr 1994

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

Jan 1994

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

Jan 1983
615-620

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.

Environmental control plot facility with manipulable soil temperature.

Jan 1983
615

Blankenship

Development of Biocontrol Technology to Manage Aflatoxin Contamination in Peanuts

Abstract

No full-text available

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