Mycotoxin effect on seed quality

Seminar-II
SANGGONDA
PG15AGR 6870
Sr. M.Sc. Agri.
DSST, UAS, Dharawad
Role of mycotoxin on seed quality parameters

Contents
1.Introduction
2.History
3. Factors affecting Mycotoxins production
4. Groups of mycotoxins
5. Case studies
A) Influence of mycotoxins on seed quality parameters
B) Control of mycotoxins by different stratergies
during storage
6.Conclusion

Mycotoxin derived from the Mycos(Greek word)
and toxicum (latin word)
What are mycotoxins?
Mycotoxins (Myco = of fungal
origin) are toxic substances produced by fungi
(molds) growing on crops/grains/seeds in field or in
storage

Mycotoxin is a convenient generic term describing the toxic
secondary metabolites produced by fungi.
They encompass a considerable variety of low molecular weight
compounds with diverse chemical structures and biological
activities.
Some mycotoxins could also be toxic to plants or other
microorganisms; but these compounds are not classified as
antibiotics of fungal origin.
Like most microbial secondary metabolites, the benefit of mycotoxins
for the fungi themselves is still not clearly defined.

Fungal growth
a. Field fungi : fungi that attack plants that grow in the field
(occurring prior to harvest) grow under special conditions.
(Fusarium)
b. Storage fungi : Storage fungi usually invade grain or seed
during storage and are generally not present in large quantities
before harvest in the field. The most common storage fungi are
species of Aspergillus and Penicillium. Contamination occurs
through spores contaminating the grain as it is going into storage
from the harvest. The development of fungi is influenced by the:
• Moisture content of the stored grain
• Temperature
• Condition of the grain going into storage
• Length of time the is grain stored and
• Amount of insect and mite activity in the grain

Modern mycotoxicology was not developed until the discovery
of aflatoxins in the early 1960s.
peanut meal causing the “Turkey X” disease that killed more
than 10,000 turkeys fed with the contaminated meal.
Because aflatoxins are a series of highly potent carcinogens
produced by commonly occurring Aspergillus flavus and A.
parasiticus.
In the last 40 years, many new mycotoxins have been identified
and characterized, and their biosynthetic origin in various fungi
elucidated.
History of mycotoxins

Storage conditions that favour production of mycotoxins:
Temperature (40 - 90o F ; 4 - 32o C)
Relative Humidity (> 70%)
Moisture (22-23% in grain)
Oxygen (1-2%)
 In general, mycotoxins are optimally produced at 24–28°C, but
some toxins such as T-2 toxin is maximally produced at 15°C.
Factors Affecting Mycotoxin Production

• Genetics and environmental and nutritional factors greatly affect the
formation of mycotoxins.
• Depending on the susceptibility of the crop, geographic and seasonal
factors, as well as cultivation, harvesting, storage, and transportation
practices, mycotoxins are found worldwide.
• In the field, weather conditions, plant stress, invertebrate vectors,
species and spore load of infective fungi, variations within plant and
fungal species, and microbial competition all significantly affect
mycotoxin production.

• Physical factors such as time of exposure, temperature during
exposure, humidity, and extent of insect or other damage to the
commodity prior to exposure determine mycotoxin contamination
in the field or during storage.
• Chemical factors including the nutritional status of the crops or
chemicals (such as fungicides) used in crop management could
affect fungal populations, and consequently toxin production
Continue Factors Affecting…….

11
• In general, mycotoxins are optimally produced at 24–28C, but some
toxins such as T-2 toxin is maximally produced at 15C.
• Contamination during crop storage may be affected by changes in
temperature and water activity, that allow ecological succession of
different fungi as water activity and temperature of stored grain
changes.
Continue Factors Affecting…….

12
• During storage and transportation, water activity (aw), temperature,
crop damage, and a number of physical and chemical factors, such
as aeration (O2, CO2 levels), types of grains, pH, and presence or
absence of specific nutrients and inhibitors are important.

Major groups of mycotoxins
1) Aflatoxins
 It produced by Aspergillus species of fungi, such as A.
flavus and A. parasiticus.
 The term aflatoxin refers to four different types of
mycotoxins produced, which are B1, B2, G1, and G2.
 Aflatoxin B1, the most toxic, is a potent carcinogen and
has been directly correlated to adverse health effects,
such as liver cancer, in many animal species.
 Aflatoxins are largely associated
with commodities produced in the tropics and subtropics,
such as cotton, peanuts, spices, and maize.

2) Ochratoxin
Ochratoxins, are produced by a number of fungi in the genera
Aspergillus and Penicillium. The largest amounts ochratoxins are
made by A. ochraceus and P. cyclopium.
 A. ochraceus and P. viridicatum (reclassified as P.
verrucosum), two species that were first reported as ochratoxin A
(OA) producers, occur most frequently in nature.
Other fungi, such as Petromyces alliceus, and A. citricus, have
also been found to produce OA. Most of the OA producers are
storage fungi and preharvest fungal infection.

3) Citrinin
It is a toxin that was first isolated from Penicillium citrinum.
It is identified in several species of pencillium and aspergillus.
Some of these species are used to produce human food stuffs
such as cheese (Penicillium camemberti), sake, miso, and soy
sauce (Aspergillus oryzae).
Although it is associated with many seeds
(wheat, rice, corn, barley, oats, rye)
Citrinin can also act synergistically with Ochratoxin A to
depress RNA synthesis.

4) Ergot Alkaloids
They are compounds produced by the Sclerotia species
of Claviceps.
 The ingestion of ergot sclerotia from infected cereals,
commonly in the form of bread produced from
contaminated flour, cause ergotism the human disease
historically known as Anthony's Fire.
There are two forms of ergotism: gangrenous, affecting
blood supply to extremities, and convulsive, affecting
the central nervous system.

5) Patulin
 It is atoxin produced by the P.expansum, Aspergillus,
penicillium, fungal species.
P. expansum is especially associated with a range of
moldy fruits and vegetables, in particular rotting apples and
figs.
Although patulin has not been shown to be carcinogenic, it
has been reported to damage the immune system in animals.
In 2004, the European Community set limits to the
concentrations of patulin in food products.

6) Fusarium
It is produced by over 50 species of Fusarium and have a
history of infecting the grain of developing cereals such
as wheat and maize.
zearalenone, it can inhibit seed germination and embryo
growth at low concentrations.
 Some of the other major types of Fusarium toxins include:
beauvercin and enniatins, butenolide, equisetin, and fusarins.

 Types of Tests for Mycotoxins
Quick Test (Qualitative)
• Immunoassays (Elisa tests)
• Thin Layer Chromatography (TLC)
Use: Detect Specific Mycotoxin
Confirmatory Tests (Quantitative)
• High Pressure Liquid Chromatography(HPLC)
Use: Determine level of mycotoxins

PREVENTIVE MEASURES
Management of Mycotoxin Contamination
• While an association between mycotoxin contamination and
inadequate storage conditions has long been recognized, studies
have revealed that seeds are contaminated with mycotoxins prior to
harvest . Therefore, management of mycotoxin contamination in
commodities must include both pre- and postharvest control
measures

• Preharvest Control
Mycotoxin contamination can be reduced somewhat by
using of resistant varieties (most effective, but not all are
successful) and earlier harvest varieties:
– crop rotation,
– adequate irrigation,
– control of insect pests.

• Significant control of toxin contamination is expected to be
dependent on a detailed understanding of the:
– physiological and environmental factors that affect the
biosynthesis of the toxin,
– the biology and ecology of the fungus,
– the parameters of the host plant–fungal interactions.

Postharvest Control
After harvest, crop should not be allowed to
over-winter in the field as well as subjected to birds and insects
damage or mechanical damage. Grains should be cleaned and dried
quickly to less than 10–13% moisture and stored in a clean area to
avoid insect and rodent infestation.

 Postharvest mycotoxin contamination is prevalent in most
tropical countries due to:
• a hot, wet climate coupled with
• subadequate methods of harvesting,
– (handling, and storage practices),
– which often lead to severe fungal growth and mycotoxin
contamination of food and feed.

I. Removal or Elimination of Mycotoxins.
Since most of the mycotoxin burden in contaminated
commodities is localized to a relatively small number or seeds
or kernels removal of these contaminated seeds/kernels is
effective in detoxifying the commodity.
Methods currently used include:
(a) physical separation by:
•identification and removal of damaged seed;
• mechanical or electronic sorting;
•flotation and density separation of damaged or
contaminated seed;
• physical screening and subsequent removal of
damaged kernels by air blowing;
•washing with water
• use of specific gravity methods

II. Inactivation of Mycotoxins.
When removal or elimination of mycotoxins is not possible,
mycotoxins can be inactivated by:
(a) physical methods such as thermal inactivation,
photochemical or gamma irradiation,
(b) chemical methods such a treatment of commodities with
acids, alkalies, aldehydes, oxidizing agents, and gases like chlorine,
sulfur dioxide, NaNO2, ozone and ammonia,
(c) biological methods such as fermentations and enzymatic
digestion that cause the breakdown of mycotoxins
Although several detoxification methods have been established
for aflatoxins, only the ammoniation process is an effective and
practical method
III. Removal of Mycotoxins During Food Processing.

Maximum amount of aflatoxins allowed in food stuffs in different
countries (μg/kg)
(Liu et al., 2006)

Mycotoxin effect on seed quality

Mycotoxin effect on seed quality

More Related Content

What's hot (20)

Similar to Mycotoxin effect on seed quality (20)

Recently uploaded (20)

Mycotoxin effect on seed quality