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Emerging mycotoxins
– should we be concerned?
M
ycotoxins are naturally occurring, secondary metabo-
lites produced by various fungi (the most prominent
being
Fusarium
and
Aspergillus
spp). Mycotoxigenic
fungi can infect a wide range of crops and produce my-
cotoxins pre- and post-harvest.
Contaminated grain can be a major health risk to humans and
animals. Essentially, all of the agriculturally important fungal
toxins were first recognised as animal diseases, and often there was
a long journey before their significance in humans was adequately
understood.
Furthermore, analytical methods for mycotoxin quantification
was limited. Presently, it is relatively easy to identify and quantify
the principal mycotoxins that affect food and feed. To ensure food
and feed safety, many countries have established regulatory limits
for mycotoxins. However, these regulations only cover some of the
known mycotoxins such as aflatoxins, fumonisins, ochratoxin A,
deoxynivalenol and zearalenone.
Emerging mycotoxins
Emerging mycotoxins are a group of chemically diverse mycotox-
ins. Despite increasing research efforts, toxicological data is scarce
and therefore no regulations exist for these mycotoxins. Emerging
mycotoxins can co-occur with each other and with the principal
mycotoxins mentioned above.
Few studies regarding the synergistic effects of co-occurring my-
cotoxins are available. This highlights the importance of continued
research of emerging mycotoxins. The most relevant and frequently
occurring emerging mycotoxins in grains that will be discussed in
this article are Fusarium toxins. Fusarium emerging mycotoxins in-
clude enniatins, beauvericin, moniliformin, and fusaproliferin.
Emerging mycotoxins
– a South African study
In South Africa, the second most occurring fungal pathogen on maize
ears is
Fusarium subglutinan
s (
Photo 1
). Prior to 2011, research and
publications reported that fumonisins, moniliformin, fusaric acid,
fusaproliferin and beauvericin were produced by
F. subglutinans
.
In 2011, the
F. subglutinans
strain that produced beauvericin was
renamed as
F. temperatum
. These fungi cannot be morphologically
differentiated, but they can be differentiated by means of sequenc-
ing (differences in DNA patterns is analysed).
The aim of our study was to determine the distribution from
different climatic zones and mycotoxigenic potential of
F. subgluti-
nans
and
F. temperatum
in subsistence and commercial maize pro-
ducing areas of South Africa. To achieve this, we studied a total of
180
Fusarium subglutinans
strains (stored at the ARC-Grain Crops
at -70°C) previously collected (2007 - 2009) from maize grain from
commercial and subsistence farmers’ fields from eight provinces in
South Africa.
To determine the occurrence of mycotoxigenic
Fusarium
spp. in
South African maize fields, eleven different maize cultivars were col-
lected from five provinces (eight localities) in the main maize produc-
tion areas of South Africa (2016 - 2017).
Fusarium
spp. were isolated
from these grain samples and identified.
Results
Of the 180 Fusarium strains (stored at -70°C), 46 strains were identi-
fied as
F. subglutinans
and 134 strains as
F. temperatum
.
Subsistence farmers (2006 - 2009)
From the 101 strains collected from subsistence farmers,
F. tempera-
tum
was more predominant in the Eastern Cape and Mpumalanga
when compared to
F. subglutinans
. In the Limpopo province no
F. temperatum
was detected and in KwaZulu-Natal an equal amount
of both species were detected.
Commercial producers (2006 - 2009)
F. temperatum
was more predominant in the Free State compared
to
F. subglutinans
. The ratio of
F. temperatum
and
F. subglutinans
was more balanced in Gauteng, Mpumalanga, North West Province
and KwaZulu-Natal.
Mycotoxin producing ability of the strains
Fungal strains were sent to Italy for mycotoxin quantification and
neither
F. temperatum
nor
F. subglutinans
produced fumonisins.
ON FARM LEVEL
Chemically diverse mycotoxins / Health risk
Integrated pest control
DR BELINDA JANSE VAN RENSBURG,
ARC-Grain Crops, Potchefstroom
1: A maize ear infected with a
Fusarium
spp.
1