Mycotoxin Research

Mycotoxin Research

Importance of Mycotoxin Research

Maize is the major staple food of the majority of the people living in South Africa, a major constituent of animal and poultry feeds in our country, and an important earner of foreign currency. However, maize remains prone to contamination by several toxigenic fungi during the pre-harvest (production), post-harvest (storage) and processing stages. These fungi have the propensity to produce some hazardous toxins such as the fumonisins, aflatoxins, zearalenone, ochratoxins, trichothecenes (deoxynivalenol and nivalenol) and diplodiatoxins (diplonine). The fumonisins, produced by Fusarium verticillioides and Fusarium proliferatum represent the most important mycotoxin threat to the local maize industry. Fortunately, the aflatoxins occur extremely rarely on South African commercial maize reducing their significance locally as a potential health threat. The isolation and characterization of the toxin(s) produced by a specific toxigenic fungus is a prerequisite for analysing the mycotoxins in agricultural commodities and foods in order to study the impact of the relevant toxin on human and animal health.

Mycotoxins comprise small-molecular-weight toxic compounds, derived from the secondary metabolism of filamentous fungi. These metabolites are produced by a number of fungi, including members of the genera Aspergillus, Penicillium, Fusarium, Claviceps and Alternaria. Several of the mycotoxins are important environmental and carcinogenic agents and are ubiquitous in a broad range of commodities, causing toxic responses when ingested by mammals (such as man and higher animals), poultry and fish. During 2005 the Council for Agricultural Science and Technology (CAST) internationally considered aflatoxins, trichothecenes, fumonisins, zearalenone, ochratoxin A (OTA) and ergot alkaloids as the most relevant for human health. The same toxins, in fact, are also very relevant to animal health.

Mycotoxins pose an enormous threat to the international trade in foods and feeds because of the worldwide distribution of toxigenic fungi in agricultural products. Post-harvest losses in the developing world, in particular, are severe because of inadequate storage facilities and the consequent poor quality of the produce. It is claimed that approximately 60% of Africa’s grain supplies are at risk owing to fungal contamination and mycotoxin formation, thereby contributing to food insecurity in Africa.

In nature, most cereal grains, oil seeds, tree nuts, fruits and dehydrated fruits are susceptible to contamination by mycotoxin-producing fungi. Not all fungal growth on plants and plant products, however, results in mycotoxin production. Therefore, the occurrence of fungi, even toxigenic ones, on foods and feeds does not necessarily imply the presence of mycotoxins. On the other hand, fungal species could be undetectable although the relevant mycotoxins could be present.

Several environmental factors such as temperature, humidity and soil or storage conditions influence the production of mycotoxins in agricultural commodities. There can be significant year-to-year fluctuations in the levels of mycotoxins in foods and feeds due to many factors such as adverse climatic conditions that favour fungal invasion, growth and mycotoxin formation.

Initially mycotoxin production was only linked to the so-called storage fungi growing saprophytically (post-harvest) on stored grains and nuts. Today, however, it is well recognized that some fungi growing parasitically on plants before harvest also have the propensity to produce mycotoxins.

Most mycotoxins are thermally stable and cannot be eliminated during food processing. These toxins induce powerful and dissimilar biological effects in humans and animals. Some are carcinogenic (aflatoxins, ochratoxins and fumonisins), mutagenic (aflatoxins and sterigmatocystin), teratogenic (ochratoxins), oestrogenic (zearalenone), haemorrhagic (trichothecenes), immunotoxic (aflatoxins and ochratoxins), nephrotoxic (ochratoxins), hepatotoxic (aflatoxins, ochratoxins and phomopsins), dermatoxic (trichothecenes) and neurotoxic (ergotoxins, penitrems, lolitrems and paxilline), whereas others display antitumour, cytotoxic and antimicrobial properties. Chronic exposure to low levels of various mycotoxins is a risk factor for human diseases including cancer and childhood stunting. The prevention of chronic exposure, particularly in developing countries such as sub-Saharan Africa and parts of Latin America, is of critical importance. Exposure to multiple mycotoxin contamination in staple food commodities enhances the negative health effects in consumer populations. Co-contamination of food and co-exposure of especially young children to multiple mycotoxins have been widely documented in low socioeconomic areas in African (Tanzania, Cameroon and Nigeria) and Latin American (Guatemala) countries, and is of particular concern.

The human ingestion of mycotoxins is due to the consumption of the mycotoxins in plant-based grains such as maize, barley and rice, coffee, nuts and their residues, and metabolites in animal-derived foods, for example aflatoxin M1 (AFM1) in milk and meat products. In addition, they have a tremendous economic impact on the animal and food/feed industry. The global health threat to mankind is based on well-documented human mycotoxicoses such as ergotism, alimentary toxic aleukia (ATA) in Russia, acute aflatoxicoses in South and East Asia, and human PLC in Africa and South East Asia. OTA is suspected of playing a role in Balkan endemic nephropathy (BEN) amongst the population living in the former Yugoslavia, and chronic interstitial nephropathy (CIN) in North Africa. The fumonisins are implicated in the aetiology of the high incidence of oesophageal cancer among the inhabitants of the former Transkei region of South Africa,China and Iran, and with clusters of birth defects, i.e. neural tube defects (NTD) such as anencephaly and spina bifida, occurring in different parts of the world such as the Texas-Mexico border. Although the role of mycotoxins in diseases among domestic animals is better established, diagnosis of the mycotoxicosis is extremely difficult owing to the numerous pharmacological effects of the causative toxins, for example aflatoxins (Turkey-X disease), fumonisins (leukoencephalomalacia in horses and pulmonary oedema in swine), ochratoxins [nephropathy in swine (Danish porcine nephropathy) (DPN)], phomopsin A (lupinosis in sheep) sporidesmin A (facial eczema in sheep) and zearalenone (hyperoestrogenism, vulvovaginitis and abortion in swine). Outbreaks of diplodiosis amongst farm animals are linked to feeds contaminated with Stenocarpella maydis. It was recently found that plants can bind mycotoxins such as the fumonisins to various organic molecules (amino acids and proteins), creating so-called masked or bound mycotoxins.

Since the discovery of aflatoxins during the 1960s, an increasing number of countries have legislated maximum levels (MLs) for an increasing number of mycotoxins with the aim of protecting both human and animal populations from the harmful effects of mycotoxin exposure. Aflatoxin remains the most widely legislated mycotoxin. At least 99 countries have regulatory limits for AFB1 or the sum of AFB1, AFB2, AFG1 and AFG2 in food and/or feed. It remains an ongoing challenge to legislators and researchers to identify practical MLs to protect the consumer, without introducing unachievable barriers to entry into the market for processors and farmers. In South Africa, world-class mycotoxin research has been done over many years at the CSIR and the South African Medical Research Council (MRC).

With regards to the fumonsins, the MLs are intended to be health protective such that exposures will be below the provisional maximum tolerable daily intake (PMTDI) of fumonisin of 2 µg/kg body weight/day set by the Joint Food and Agriculture Organization of the United Nations (FAO)/World Health Organisation (WHO) Expert Committee on Food Additives (JECFA). In a 2003 survey published by the FAO, six countries had already established ML or guideline values for maize. Of these, Bulgaria (for FB1+FB2), Cuba (for FB1), Iran (for FB1+FB2) and Switzerland (for FB1+FB2) had MLs of 1000 μg/kg, whereas France had a target for FB1 of 1000 μg/kg and a ML of 3000 μg/kg. The USA had guidance levels for total fumonisins (FB1+FB2+FB3) between 2000 and 4000 μg/kg, depending on the individual maize products. Subsequently, MLs have been established for FB1+FB2 by the European Commission. These range from a ML of 4000 μg/kg in unprocessed maize,1000 μg/kg for maize intended for direct human consumption, 800 μg/kg in breakfast cereals and snacks to 200 μg/kg in foods for babies and young children. More recently, international consensus has resulted in MLs being set for FB1 and FB2 combined by the Codex Alimentarius Committee. These were set at 4000 μg/kg for raw maize and at 2000 μg/kg for maize flour and maize meal. The MLs are intended to be applied to maize in local or international trade. The government department responsible for food safety in South Africa, the National Department of Health, has adopted these ML values into South African food safety regulations.

Development of a Research Strategy

Based on its mandate to support and facilitate research on behalf of the maize industry, the Maize Trust approved a strategy for mycotoxin research aimed at the “Sufficient and sustainable production, storage and processing of healthy and high quality maize for the food and feed industries, consumers in South Africa and export markets.” in October 2009. A business plan and research strategy was subsequently developed at a meeting at STIAS, SU on 26 January 2010. The event comprised researchers from ARC/GCI, MRC/PROMEC, SAGL, Stellenbosch University and the management of the MF.

 

Guiding Principles:

  • The MF is committed to support cutting edge research which is guided by internationally accepted standards.
  • The MF is committed to draw together teams of excellent researchers through inter-institutional research activities.
  • The MF is committed to fostering interdisciplinary and cross fertilizing collaboration.
  • The MF requires that all proposals be peer reviewed to ensure research excellence, scientific merit and relevance to the South African maize industry.
  • The MF wishes to establish formal and innovative collaborative agreements and synergies with statutory bodies, SAGL, the National Metrology Institute of South Africa (NMISA), government departments, the NRF including THRIP, and universities to extend its research undertakings.
  • The MF envisages that the effective implementation of the Strategy as supported by the Business Plan will lead to the creation of a DST supported virtual Centre of Excellence on Mycotoxin Research in Maize (and other cereals) in South Africa by 2012.

 

Issues Addressed by the Research Strategy

  • To define the key research areas of mycotoxin research and their rationale in the South African context.
  • To recognize and involve the leading South African scientists involved in maize–related mycotoxin research and their areas of expertise.
  • To identify laboratory facilities and equipment available for mycotoxin research in South Africa.
  • To develop a management system for selecting and evaluating a number of research projects to comprise the mycotoxin research portfolio of the MT.
  • To ensure the cost effective use of research funding supplied by the Maize Trust.
  • To promote synergy and communication among investigators by promoting interdisciplinary and inter-institutional research directed at local problems.
  • To create an environment conducive to jointly sponsored mycotoxin research in South Africa.
  • To develop capacity, both human and facilities to meet the research needs of South Africa’s maize industry and be globally competitive.

 

Strategic Objectives for Mycotoxin Research at the Maize Forum (as accepted in the Strategy Document of August 2009)

  • To support the establishment of the magnitude of mycotoxin contamination of maize during the stages of its production, storage, and processing in South Africa.
  • To support the regular monitoring of the occurrence of the fumonisins, aflatoxins, zearalenone, and trichothecenes (DON and NIV) in locally produced and imported maize.
  • To support the determination of the factors which contribute to mycotoxin contamination during the production (pre-harvest), storage (post-harvest) and processing of maize.
  • To support the development of practical, affordable and environmentally sound methods to manage toxigenic fungi in maize, with particular emphasis on the introduction of resistance in local maize cultivars.
  • To support the development of sound mycotoxin risk management practices in the maize supply chain to ensure the delivery of safe products to the consumer.

 

Key Areas of Mycotoxin Research in South Africa

Scientists involved in mycotoxin research and the management of the Maize Trust discussed mycotoxin research at workshops held at Stellenbosch in January 2010 and Pretoria in March 2019, and the following seven key areas of mycotoxin research and their rationale were proposed. Substantial consultation occurred between researchers representing the various institutions and disciplines involved in mycotoxin research. These seven key areas should provide additional direction to the funding of research and be conducive to collaborative research between South African researchers as well as involving international experts.

 

  • The importance of mycotoxins as contaminants of maize and maize-derived products, their role in the aetiology of animal and human diseases, and intervention methods, including a passport system for the maize value chain, and appropriate communication to stakeholders to reduce the exposure to mycotoxins

 

Mycotoxins are naturally occurring fungal contaminants produced in maize and are associated with several animal disease syndromes. They pose health risks to humans as they have been implicated in the development of cancer and neural tube defects. Based on these findings, risk assessments have been performed by the FAO and the WHO, while IARC has classified some mycotoxins such as aflatoxins, ochratoxins and fumonisins as either human carcinogens or possible human carcinogens. Based on toxicological studies and the use of safety factors, the maximum tolerable daily intakes for certain mycotoxins have been defined while for others, such as aflatoxins, levels must be as low as reasonably achievable, due to the absence of a no observed effect level. Mycotoxins in maize are a health risk as maize is a staple food commodity in South and southern Africa, and known to be frequently contaminated with high levels of mycotoxins, especially fumonisins. High risk population groups include subsistence maize farming communities where maize is consumed in large quantities on a daily basis and undiversified diets exist. The ultimate aim will be to reduce mycotoxin exposure thereby minimizing the risk in adults, children and babies, who are often weaned on maize-based foods. Recent developments regarding mycotoxin reduction by simple intervention methods and the utilization of urinary and/or serum biomarkers of exposure provide ample opportunities to effectively integrate mycotoxin contamination of maize and the level of exposure which will form the basis of applicable intervention programmes. Additional approaches included health promotional and educational campaigns involving the community to ensure the sustainability of the mycotoxin reduction intervention programmes.

 

  • The importance of reliable and accurate mycotoxin analysis, including unbiased sampling, method development, standardisation of analytical and detection methods, and an accredited mycotoxin reference laboratory.

 

Introduction to the need for reliable and accurate mycotoxin analysis

The provision of reliable and accurate chemical analytical results is of fundamental importance for the provision of the basic data needed so that meaningful and correct decisions can be made in the applications and policy flowing from these results. Adequate resources should be available for maintenance of an infrastructure that provides this information and for the upgrading of methods and instrumentation to meet the ongoing developments in mycotoxin analytical research. Chemical analysis of mycotoxins in South Africa is performed by a number of laboratories, using a range of screening, semi-quantitative or fully quantitative HPLC-based methods, which meet the requirements of various local industries or exporters. A very few can undertake the type of multi-mycotoxin analytical methods by HPLC with tandem mass spectrometry, which are currently being adopted in many laboratories of the developed world and South Africa’s trading partners. The current costs for multi-mycotoxin analyses are high and impact negatively on conducting large scale research projects.

Regular monitoring of mycotoxin levels in food and feed is necessary to determine the extent of contamination. For the maize industry the monitoring programme should cover a representative number of samples tested for a range of mycotoxins including at least the following 5 mycotoxins: aflatoxin B1, deoxynivalenol, zearalenone, fumonisins and OTA.

 

Importance of the analysis of masked and bound mycotoxins

At present, South African scientists do not have the capacity to analyze the masked and bound mycotoxins formed in maize. Local researchers in collaboration with the Southern African Grain Laboratory (SAGL) intend to develop the expertise to elucidate the structures of these complex molecules, and to develop appropriate analytical methodology.  The South African researchers benefit from collaboration in large international collaborative projects such as the MoniQa project (Monitoring and Quality Assurance in the Food Supply Chain) through the International Association for Cereal Science and technology (ICC) and by collaboration with several international experts.

The masking and binding of mycotoxins, including fumonisins, can shed some light on their stability and toxicity in maize-based foods.  Apart from the free mycotoxins which are commonly found, mycotoxins also occur as conjugated compounds. Two types occur namely a soluble conjugated form or the so-called “masked” type, and an insoluble conjugated form also known as the “bound” type. Several mechanisms exist which can convert free mycotoxins into the masked or bound form.  These involve conjugation during plant growth (the typical case with fumonisins), fungal conjugates (fungi excreting mycotoxins as part of a larger molecule), food processes conjugates (treatments such as heat processing induce binding of mycotoxins to other organic molecules especially proteins and amino acids) and mammalian conjugates, where the mycotoxin is bound by the serum albumin.  It has emerged that mycotoxins are often not destroyed, but rather bound during food processing.  A typical example is the reaction of fumonisin B1 in the presence of reducing sugars to yield N-carboxymethyl fumonisin. This typically occurs in the wide range of high temperature extruded maize products including snacks, breakfast cereals and instant porridges for weaning foods.

Other food processing systems such as fermentation and acidic processes have shown to release large quantities of these bound mycotoxins, and it is now generally believed that the human digestive tract also plays a major role in releasing mycotoxins from their conjugated forms, with resulting increases in toxicity much higher than initially believed. In South Africa the measurement of mycotoxin conjugates remains a challenge and places a significant limitation on the understanding of the interaction between fungal contaminants in the maize value chain and the expression of the mycotoxin, linked to the health of consumers.

Bound fumonisins are present in unprocessed maize, but the exact nature of the substances is not understood. The bound fumonisins are commonly associated with the Osborne prolamin and glutelin fractions from maize. The elucidation of the formation of the bound fumonisins and their molecular structures remain a great challenge.

 

Importance of a national accredited mycotoxin analytical laboratory

In addition to the monitoring programme, there is also the need for an accredited analytical facility to support mycotoxin research. Such a facility needs to be able to supply accurate reliable analytical data at an affordable price to researchers and industry in South Africa and should include the following services.

The Southern African Grain Laboratory (SAGL) is a South African National Accreditation System (SANAS) accredited facility (Accreditation no T016), functioning in accordance with the recognized international standard, ISO/IEC 17025:2017. Accredited analytical chemistry methods include the detection and quantification of multiple mycotoxins in food and feed (Aflatoxins G1, B1, G2, B2 and total; Deoxynivalenol and 15- ADON; Fumonisins B1, B2 and B3; Ochratoxin A; T2 and HT-2; Zearalenone). The Mass Spectrometry Unit of the Central Analytical Facility of Stellenbosch University also offers multi-mycotoxin analyses as well as assistance with the development and validation of analytical techniques. Both laboratories offer training to analysts and students in extraction methods, HPLC as well as LC-MS/MS quantification of multi-mycotoxins in grains.

Research into new analytical techniques (methods), provision of routine methods to routine analytical laboratories, support laboratories in quality assurance based on ISO 17025, organize inter-laboratory comparisons, offer technical advice to laboratories, identify and determine sources of disagreements between laboratory’s results, offer training opportunities and assist government with technical and scientific expertise.

The National Metrology Institute of South Africa (NMISA) maintains and develops primary methods for chemical analysis to certify reference materials for SA and the region. Their capabilities are benchmarked through participation in international proficiency tests. As the NMISA is a public entity funded by the Department of Trade and Industry – they offer traceability to the measurement laboratories in support of trade and industry. In order to provide a mechanism for scientific and technical cooperation in the analysis of organic contaminants in grain and related products, the SAGL and NMISA, agreed to pursue scientific and technical cooperation in the accurate analysis of organic contaminants, such as mycotoxins in grain and related products.

 

  • Importance of regulations/legislation for controlling mycotoxins in foods and feeds.

 

Mycotoxins are a diverse range of fungal secondary metabolites with widely differing chemical structures. Many are genotoxic, carcinogenic, teratogenic, oestrogenic, haemorrhagic, immunotoxic, nephrotoxic, hepatotoxic or neurotoxic. As a consequence, mycotoxin contamination of the food supply represents a health risk to the population, the nature and extent of which depends on the mycotoxins present, their respective levels of contamination and the degree to which the contaminated foodstuffs are consumed. For these reasons, many national governments, particularly in the developed world, have instituted legislated regulations for both their national food supply and for the importation of foods into their markets. In certain instances, these regulations are complex and have been designed to take account of the lowering of contamination levels in certain unprocessed cereals that occurs during the processing chain, the lowest regulated levels being reserved for foods destined for direct human consumption. The concept of the graded regulation is that should the raw material or cereal meet the standards required, the final products should similarly meet the lower levels. On the other hand, maize sold by small scale or emerging farmers in small local informal markets generally falls outside regulatory controls, which can represent a serious challenge to food safety.

 

  • Importance of expert identification, characterization and detection of mycotoxin-producing Fusarium

 

Several Fusarium spp. have been associated with diseases and mycotoxin production in maize. F. verticillioides, F. graminearum, F. proliferatum and F. subglutinans cause ear rot, seedling diseases, and root and stalk rots. Fumonisins are produced mainly by F. verticillioides and F. proliferatum, while F. graminearum produces the toxins deoxynivalenol and zearalenone. The threat of mycotoxins becomes more important if food supply is limited, and animals and humans are forced to consume mycotoxin-infected food. The taxonomic classification in Fusarium has been refined in the past two decades, especially with the availability of advanced methods in molecular biology. Reliable and rapid identification and detection procedures, thus, need to be developed and established to determine maize kernel infections with mycotoxin-producing Fusarium spp. The identification of large numbers of infected kernels to quantify pathogen levels after harvest is a laborious, expensive and time-consuming exercise. Molecular technologies, such as multiplex PCR and quantitative real-time PCR, can help to significantly reduce the time and effort required to accurately measure toxin-producing Fusarium spp. in maize. In the modern era of molecular biology, these techniques have also become essential for studies on the distribution, epidemiology, ecology and control of Fusarium spp. and their mycotoxins in maize. Despite their significant value, molecular techniques should serve as additional tools to conventional mycological methods in studying Fusarium species only, and not entirely replace them.

 

Relevance of fungal genetics and genomics, especially that of Fusarium verticillioides

Fusarium verticillioides is a sexually reproducing fungus that causes Fusarium ear rot and may result in mycotoxin contamination of maize grain. The fungus has an endophytic nature that can infect maize plants without causing any visual symptoms, while high toxin levels may be present in maize ears. Due to this unpredictable behaviour and because individual isolates of F. verticillioides have the ability to produce varying levels of mycotoxins in maize, populations of F. verticillioides strains, rather than individuals, should be investigated as pathogens and toxin producers in maize. Investigating the molecular regulatory system and toxigenic potential of F. verticillioides in order to ascertain why certain strains produce different amounts of fumonisins is, therefore, necessary. Furthermore, the genetic structure of the fungus in South Africa, and its ability to cause different levels of Fusarium ear rot, is unknown. Isolates that are non-pathogenic and/or non-toxigenic can form important components of a future disease management strategy. Whether fungal virulence and toxin production in F. verticillioides are functions of pathogenic fitness and/or the genomic composition of the fungus, the physiological state of the plant, or prevailing environmental conditions, is still unknown. A better understanding of the genetic composition and genomics of F. verticillioides and the maize plant, and the interaction between plant and pathogen using molecular and genomic tools, might lead to the development of novel disease management practices that prevent Fusarium ear rot and fumonisin contamination of maize.

 

  • Importance of epidemiology and pre-harvest management of Fusarium ear rot and mycotoxin production in maize.

 

Various maize ear rot pathogens that produce mycotoxins under a variety of practices and conditions occur in South Africa. The three most important ear rot-causing organisms include F. verticillioides, F. graminearum and Stenocarpella maydis. Ear rot fungi primarily produce mycotoxins during crop development and harvest, and only some will produce toxins under favourable conditions during storage. In the field, mycotoxin contamination in maize depends on the coincidence of host susceptibility, presence of inoculums, environmental conditions favourable for infection and, in some cases, vector activity. As the interaction between these factors affects the incidence and severity of ear rots and mycotoxin production, disease development and mycotoxin production in the field may yield contradictory results, dependent on the conditions under which trials were conducted. Many agricultural practices, including hybrid selection, crop rotation, tillage, planting date, insect management, chemical control and management of irrigation and fertilization, can affect fungal infection and mycotoxin accumulation in maize grain. Under endemic conditions the use of integrated management systems will go a long way in ensuring low mycotoxin production and food safety. When environmental conditions or genotypes planted are highly favourable for a specific ear rot epidemic and increased mycotoxin contamination, cultural practices alone are often not sufficient to prevent unacceptable levels of contamination and alternate control strategies need to be included in the integrated management system. Mycotoxin management methods used in commercial agricultural systems may not always be suitable for use in subsistence production systems because of the differences in food systems and technological infrastructure. Understanding holistic epidemiological models, which take all factors that contribute to disease development into consideration, will enable us to develop realistic integrated control programs to reduce mycotoxin levels in various farming systems.

 

  • Evaluation and improvement of maize for resistance to verticillioides and fumonisin contamination.

 

The planting of resistant cultivars, as part of an integrated disease management strategy, can be considered the most efficient approach to reduce maize ear rot diseases and minimise the risk of fumonisin accumulation in maize. Maize hybrids resistant to Fusarium ear rot and fumonisin contamination have been found internationally, but no highly resistant genotypes suited to the South African production regions are known to exist and, thus, have to be developed. Once available, these cultivars will provide producers with affordable, practical and environmentally sound means of disease control. Plant resistance to pathogens can be obtained through conventional (plant breeding) and unconventional (genetic engineering) strategies. For conventional breeding, inbred lines with resistance to Fusarium ear rot and fumonisin contamination first need to be identified for breeders to develop locally adapted hybrids, as hybrids grown outside of their adapted range are known to accumulate high concentrations of fumonisin. Such inbred lines should also be evaluated for resistance against other important ear rot diseases, such as Diplodia (caused by S. maydis) and Gibberella ear rot (caused by F. graminearum). While conventional breeding is time-consuming and labour-intensive, unconventional breeding offers a faster alternative for developing maize plants with resistance to ear rot pathogens and their mycotoxins. Genetic engineering is the most attractive unconventional strategy available to reduce the production of fumonisins in maize, and mutation breeding has been used before to find valuable plant selections with superior properties, such as herbicide-resistance. Resistance in maize cultivars best adapted to South African growing conditions can also be enhanced by inducing their natural defence responses by treating them with biotic and abiotic resistance inducers.

 

  • The importance of storage conditions and the postharvest contamination of maize and maize products by fungi.

 

The maize value chain consists of all the steps from developing of the seed by plant breeding technologies to the end products destined for human and animal consumption.  This includes all the steps of transportation, storage, processing and production  Recent research has shown that inside maize mills, there are definite trends and significant development of storage fungi at specific processing unit operations causing a shift in the amount and type (species) of fungal spore populations in the end food products. These storage fungi are currently a major cause of food spoilage in both the commercial and emerging markets, especially during storage and transport.  Although mycotoxins are not necessarily produced from these storage fungi, the vegetative forms of the fungi cause severe spoilage resulting into post-harvest losses and a serious risk to food security. The interaction between these fungi, the triggers necessary for their germination and/or mycotoxin production, and the links with the formation of mycotoxin conjugates and the eventual risk to the consumers are poorly understood.  Specific proposed topics of research include:

 

  • The study of the mechanisms which trigger fungal contamination and the routes of contamination in mills and processing plants. These investigations should result in the development of appropriate management and cleaning/preventative practices.
  • The investigation of the growth patterns of storage fungi during transport and warehousing systems (including silos).
  • The development of novel rapid and accurate methods for the detection of fungal contamination.
  • The study of the toxicity of mycotoxin conjugates in human and animal models.

 

Mycotoxin Research Workshop 2019

In a mycotoxin research workshop held in Pretoria in March, 2019 it was noted that the current objectives appear to be sufficient to address the main concerns. The following recommendations were, however, presented to the Maize Trust and the Mycotoxin Research Review Panel to take into account when considering proposals.

 

Recommendations:

  • Although mycotoxins can be detected professionally and good quality control measures are in place, there is a need for the standardisation of analytical and detection methods.
  • Sampling is an important protocol for both commercial and experimental purposes, the latter also needs to be standardised and training courses offered to students.
  • Mycotoxin profiling has to be assessed and benchmarked.
  • Disease screening and phenotyping are important – less complicated and cheaper methods should be investigated.
  • Environment studies have to continue and should be enhanced to determine the role of the environment in mycotoxin production.
  • Resistance breeding plays a vital role in combatting the occurrence of mycotoxins at grass root level and interaction with seed breeders should be improved.
  • Agronomy remains important to assist maize producers to mitigate the risk of mycotoxin occurrence at commercial, small-holder and subsistence production levels.
  • The importance of the registration of chemicals and fungicides against target pathogens should not be ignored, but the results of current research on this topic are to be taken into consideration.
  • The risk of mycotoxins in different storage facilities and on imported maize has to be assessed.
  • Research on the mitigation of the exposure risk of consumers to mycotoxins remains important and should not be ignored.
  • The development of a passport system for the maize value chain should be supported.
  • Research results must be communicated to industry and the interaction between industry and researchers must be enhanced.
  • An economic impact study could be considered to determine the focal areas for mycotoxin research funding by the Maize Trust.
  • Although transparency and awareness are important, the publication of research results should not harm the sustainability and competitiveness of the industry.

 

The management of Maize Trust mycotoxin research grants

The Maize Trust Mycotoxin Research programme operates on an annual call basis. It is acknowledged that many projects require several years (more than one year) of funding to deliver their full potential, however, a project retains its title throughout the period of funding. Funding over more than one year will require that agreed upon outputs are achieved and reported.

Applicants are invited to submit Research Proposals (RPs) before 30 April. The RPs are subjected to a process of peer review involving proposal review forms. South African and international experts are invited to undertake the adjudication of the RPs. The proposal review forms and the RPs are evaluated and prioritised by a Mycotoxin Research Review Panel (MRRP) comprising experts. Sufficient feedback will be given to all proposers of the RPs. A successful outcome enables an application to proceed to a presentation to the MRRP and Maize Trust in September. The final decision is taken by the Board of the Maize Trust in November. The timeline from submission of a proposal to a decision for funding is expected to be 6 months. For more information about the application process and form, norms and conditions for financial support, and reporting systems, click on the relevant hyperlink.

Mission and Strategic Objectives

Mission of the Maize Trust Mycotoxin Research Program

World-class mycotoxin research undertaken at South African universities and research institutions in order to ensure that safe maize is supplied to the food and animal feed industries, consumers and export markets.

Strategic Objectives for Mycotoxin Research

  • To establish the magnitude of mycotoxin contamination of maize during the stages of its production, storage, and processing in South Africa.
  • To regularly monitor the occurrence of the fumonisins, aflatoxins, zearalenone, and trichothecenes (DON and NIV) in locally produced and imported maize.
  • To determine the factors which contribute to mycotoxin contamination during the production (pre-harvest), storage (post-harvest) and processing of maize.
  • To develop practical, affordable and environmentally sound methods to manage toxigenic fungi in maize, with particular emphasis on introducing resistance in local maize cultivars.
  • To support the development of sound mycotoxin risk management practices in the maize supply chain to ensure the delivery of safe products to the consumer.

Mycotoxin Research Review Panel (MRRP)

Prof Zakkie Pretorius, Research Fellow, Department of Plant Sciences, University of the Free State (convener)

 

Dr JF (Hanneke) Alberts, Lecturer, Department of Food Science and Technology, Cape Peninsula University of Technology

 

Dr Magdeleen Cilliers, Policy and Research Officer, SANSOR

 

Dr Miekie Human, Research and Policy Offcier, Grain SA

 

Dr Gert van Coller, Professional Scientist (Plant Pathology), Directorate: Plant Science, Research and Technology Development, Western Cape Department of Agriculture

Publications and Reports

Reports are uploaded on an annual basis.

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