Food, feed, and the future - A growing challenge for farmers

FOOD, FEED AND THE FUTURE A Growing Challenge for Farmers

Rosie L. Latham & Neil A. Brown Milner Centre for Evolution, Department of Life Sciences, University of Bath, UK Visit Neil Brown — The University of Bath's research portal

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Toxigenic fungi contaminate our major cereal crops with a range of harmful mycotoxins, which threaten human and livestock health1.

Despite monitoring systems used to prevent acute exposure, Aspergillus and Fusarium mycotoxins

Additionally, changing climates and

still threaten food and animal feed security2.

their influence on mycotoxins pose an increasing risk to the safety of our food and feed cereal industry3,4.

Quick Facts!

Aspergillus and Fusarium contaminate our major cereal crops with an array of harmful mycotoxins.

Despite best efforts to protect our crops, it is estimated that 60-80% crops are contaminated with mycotoxins.

Mycotoxins cause significant economic costs through the associated impacts on crop yields, animal productivity, and international trade5.

What are MYCOTOXINS and where do they come from?

Mycotoxins are toxic compounds naturally produced

Mycotoxins are commonly found in these cereals8

by fungi and pose a threat to human and animal health even at low concentrations1,6.

Aspergillus mycotoxins

There are approximately 300–400 known mycotoxins, with some of the most concerning being produced by

Aspergillus and Fusarium species1.

These fungi produce mycotoxins such as aflatoxins, deoxynivalenol, fumonisins, T-2 and HT-2 toxins, and zearalenone7,8.

Fusarium mycotoxins

Wheat Maize Rice Sorghum Oats

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Aspergillus flavus and Aspergillus parasiticus are opportunistic pathogens of cereals both in the field and during crop storage.

Their most notorious products are aflatoxins (AF), which are classified as Class I human carcinogens9,10.

Fusarium species are common in soils and infect crops in the field.

Fusarium head blight (FHB) is regarded as one of the most devastating fungal diseases in cereals and produces mycotoxins, such as deoxynivalenol (DON), nivalenol (NIV), T-2 and HT-2 toxins, zearalenone (ZEN) and fumonisins (FUM)8.

Health impacts Mycotoxin contamination is widespread, with a significant percentage of crops exceeding safety limits. This is of particular concern due to the human health impacts these mycotoxins can cause4.

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FUSARIUM Fusarium species produce mycotoxins, such as DON and ZEN, that significantly reduce crop yields and pose health risks11-14.

Deoxynivalenol (DON) disrupts protein synthesis, immune responses, and induces apoptosis15.

Its adverse effects on mammalian health cause symptoms such as vomiting, reduced appetite, stunted growth, and developmental delays16.

DON is not static, as it transforms into DON-3-β-d-glucoside (DON-3G) within cereals.

DON-3G appears less harmful, but gut bacteria can reverse this transformation, resurrecting the threat17. This ‘masked’ mycotoxin may secretly contribute to an increased total dietary mycotoxin burden.

ASPERGILLUS The most notorious products associated with Aspergillus are aflatoxins, which are classified as Class I human carcinogens9,10.

Aflatoxins contribute to cancer but also cause digestive issues and reproductive problems.

Aflatoxin B1 (AFB1) leads to weight loss, weakened immune responses, growth impairments, and even hepatocellular carcinoma or liver cancer18.

Mammals convert digested AFB1 into AFM1 that is excreted in their milk.

The consumption of AFM1-contaminated milk also poses health risks, including stunted infant growth and increased susceptibility to infectious diseases19.

Outbreaks can disrupt the entire milk supply chain4,20.

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SERIOUS IMPACTS ON HEALTH Gastrointestinal disorders Hepatocellular carcinoma

Damage to DNA Immunosuppression

Contaminated milk

Growth impairment Anorexia

AFB1

AFM1

Economic impacts Both Aspergillus and Fusarium species can

However, this downgrading of contaminated cereals

infect cereal crops in the field, inhibiting crop

from food-to-feed reduces profit for the growers.

development, affecting grain production, and resulting in yield losses3,4,14,21,22,23.

Outright crop rejection also results in greater profit losses and causes

Regulatory bodies, such as the EU Commission,

additional costs associated with

establish legal thresholds to mitigate these

hazardous waste disposal25.

risks24.

Mycotoxin limits depend on their entry into food or feed supply chains and the intended consumer.

2 µg of aflatoxin/kg and 750 µg of DON/kg are permitted for direct human consumption.

20 µg of aflatoxin/kg and 8000 µg of DON/ kg are allowed in animal feed20,21.

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Aspergillus and Fusarium mycotoxins cost € billions Recent findings bring to light the substantial economic impact of only two mycotoxins, aflatoxins and DON, on cereal farming.

Between the years 2010 and 2019, approximately 75 million tonnes of wheat (5% of wheat for human consumption) exceeded the limit for DON. This resulted in a financial loss of €3 billion due to downgrading to animal feed3.

Similarly, aflatoxins also caused downgrading of wheat destined to human consumption by 4.2% with an estimated additional €2.5 billion in losses4.

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Cereals, a cornerstone of human contributing 40% of energy and protein intake26, and are particularly vulnerable to mycotoxin contamination.

In European food cereals, DON was frequently detected across common cereals, with 68% of maize and 48% of wheat contaminated4.

Wheat, maize, barley, rice and sorghum have a combined cropping area of an estimated 700 million hectares globally26.

Food & Feed Of particular concern were the high average levels of DON found in maize, where 28% of cereals had DON levels above the safety threshold (750 µg/kg) for human food3,4,27,28.

In wheat, DON was above the safe threshold levels in 5% for human food (750 µg/kg), and in 2% above the guide for animal feed3,4,27.

Aflatoxin

DON

Wheat

Wheat

Rice

Rice

Oat

Oat

Maize

Maize

Barley

Barley Below food limits

Above food limits

Above feed limits

Figure 1. Contamination levels of food grains differ by grain for DON and aflatoxins. High levels of aflatoxin and DON contamination of food and feed cereals show that maize is of most concern4.

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Southern Europe, with its predicted hot and dry spells, may witness increased Aspergillus infections and aflatoxin contamination3,32.

CO₂ can impact host crop susceptibility, as elevated CO₂ can downregulate plant defences11.

Temperature Aspergillus flavus thrives in hot, dry environments, with an optimum temperature range between 28°C and 37°C29.

Fusarium graminearum prefers warm and moist conditions, with an optimal growth temperature between 20°C and 25°C30.

Water As climate change unfolds, certain regions may experience more severe droughts or alternatively increased precipitation, with profound consequences for mycotoxin contamination.

Northern Europe is expected to receive more rainfall3,33 making more favourable conditions for Fusarium outbreaks and mycotoxin contamination.

CO2

Increased CO₂ levels, a predicted outcome of climate change, have been shown to promote cereal disease severity and mycotoxin contamination10,31.

Fungicides Sub-optimal fungicide exposure can promote mycotoxin production, particularly AFB134.

Climate change can also influence the emergence pathogens with reduced fungicide efficacy in higher temperatures35.

This will make controlling outbreaks of disease more difficult and threaten safe grain production.

Figure 2. Summary of the environmental influence on Aspergillus and Fusarium3,4.

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Climate Change and MYCOTOXINS As discussed, we now know that fungal growth, virulence, and their mycotoxins are dependent on environmental conditions. Therefore, it is urgent to understand how climate change can threaten food and feed safety in the future.

Aflatoxins are predicted to become a major food safety issue in maize, especially in countries where a rise in temperature, together with increased CO2 levels, and droughts are predicted to occur36.

The optimum growth and mycotoxin production conditions show F. graminearum favoured by warm wet and A. flavus hot dry environments30.

Climatic events, such as in northern Italy, have already been seen throughout the last decade in maize-growing regions prior to aflatoxin outbreaks37.

Environmental changes threaten to increase the intensity and spread of mycotoxin contamination in Europe.

This issue requires efforts in the surveillance and control of mycotoxigenic fungal pathogens, to mitigate the risks they pose to sustainable safe cereal production.

Favourable conditions Aspergillus

Fusarium

Warm Wet Dry

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What are the future challenges?

Co-contamination raises pressing questions about the health implications of low level exposure to multiple mycotoxins.

Johns (2022) found that in European wheat 25% of food and 45% of feed wheat containing DON tested positive for multiple FHB mycotoxins3.

Mycotoxins can undergo partial detoxification within their host plants or animals, resulting

HT-2 ZEN T-2

NIV DON

in the formation of ‘masked mycotoxins’.

These masked variants are

Regional barriers that have prevented disease

challenging to detect and their

spread in the past (topography, distance,

presence in cereals introduces

climate) are being removed. Climate change,

diverse economic and health

altered agronomic practices, and increased

impacts throughout our food

global transportation, have made it possible

and feed supply chains38.

for fungal pathogens to enter new regions.

Why test for pathogens that have never been recorded in an area before?

Favourable conditions are expanding geographically. For example, some Fusarium species such as F. verticillioides, are expanding their range to higher latitudes in Europe due to warming climates and increased maize cultivation in those regions.

This expansion adds to the complexity of FHB management, as regions previously unaffected may now face heightened risks3.

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Why is keeping an eye on these MYCOTOXIN threats challenging?

Traditional testing systems may not be

Mycotoxin monitoring systems do not provide

effective in identifying masked mycotoxins

knowledge of the changing pathogen populations,

or other Fusarium/Aspergillus mycotoxins.

impeding our ability to understand what is

Using more sensitive and accurate detection

driving outbreaks or increased threat levels.

techniques is imperative to assess the true extent of mycotoxin contamination38.

Changing agricultural practices influence

Global data on mycotoxigenic fungi and crop contamination is patchy. This hinders the improvement of holistic approaches to understand

the likelihood of outbreaks. For instance,

and mitigate their impact. The absence of data

increased use of minimum tillage farming,

is not an absence of a mycotoxin threat.

agricultural composting, and the cultivation of maize, can provide an accessible home for

Aspergillus and Fusarium to sporulate and to overwinter, increasing disease pressure and the risk of mycotoxin contaminations39.

Infections can occur at various stages of crop growth, from seedling to post-harvest storage. What frequency of contamination is realistic and affordable to growers to maintain healthy safe crops?

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Conclusions Toxigenic fungi, such as Aspergillus and Fusarium species, contaminate cereal crops with harmful mycotoxins, posing a threat to human and animal health.

Mycotoxin contamination is widespread, with a significant percentage of crops exceeding safety limits.

Despite efforts to prevent crop diseases, aflatoxins and deoxynivalenol still contaminate cereals, affecting food and animal feed security.

More research into improved testing is required to understand the risk from masked mycotoxins and co-contaminants.

Changing environments can increase the risk of cereal infection and mycotoxin contamination. Leading to increased economic costs and health issues.

Co-ordinated research, industry, and governance efforts are needed to forecast and mitigate the growing mycotoxin threats.

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