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a worldwide distribution, commonly associated with leaves, wood, cereals, and
other grasses. The species of these fungal genera are known to produce some dangerous mycotoxins such as cytochalasins and tenuazonic acid (TA). Members of the
genus Fusarium produce a range of chemically different phytotoxic compounds,
such as fusaric acid (FA), fumonisins (fumonisin B1, FB1), beauvericin (BEA),
enniatin (ENN), moniliformin (MON), and trichothecenes. These possess a variety
of biological activities and cause morphological, physiological, and metabolic
effects including necrosis, chlorosis, growth inhibition, wilting, and inhibition of
seed germination and effects on calli (Desjardins and Hohn 1997).
Table 12.1 summarizes the general classes of mycotoxins with their producing
fungal genera/species and chemical groups. Some of these mycotoxins are phytotoxic and others are non-phytotoxic. Mycotoxins with phytotoxic properties will be
addressed below on the basis of their producing species. This review provides
insight into characterization and evaluation of mycotoxins as phytotoxins. For each
of the diverse groups of mycotoxins, we will give examples indicating history and
fungi production with a focus on their modes of action and phytotoxic effects on
several morphological and biochemical processes.
12.2 Types of Mycotoxins
There are five mycotoxins or groups of mycotoxins that occur quite often in food:
deoxynivalenol/nivalenol, zearalenone, ochratoxin, fumonisins, and aflatoxins. The
fungi that produce mycotoxins in food fall broadly into two groups: those that
invade before harvest, commonly called field fungi, and those that occur only after
harvest, called storage fungi. There are three types of toxicogenic field fungi: plant
pathogens such as Fusarium graminearum (deoxynivalenol, nivalenol); fungi that
grow on senescent or stressed plants, such as Fusarium moniliforme (fumonisin)
and sometimes Aspergillus flavus (aflatoxin); and fungi that initially colonize the
plant before harvest and predispose the commodity to mycotoxin contamination
after harvest, such as Penicillium verrucosum (ochratoxin) and A. flavus (aflatoxin)
(Tola and Kebede 2016).
12.3 Occurrence and Toxicity of Mycotoxins
Mycotoxins are poisonous chemical compounds and secondary metabolites produced by fungus or molds. Those mycotoxins that do occur in food and/or feedstuffs
have great significance in the health of humans and livestock. Since they are produced by fungi, mycotoxins are associated with diseased or moldy crops, although
the visible mold contamination can be superficial. The effects of some foodborne
mycotoxins are acute symptoms of severe illness appearing very quickly. Other
12 Fungal Mycotoxins
a worldwide distribution, commonly associated with leaves, wood, cereals, and
other grasses. The species of these fungal genera are known to produce some dangerous mycotoxins such as cytochalasins and tenuazonic acid (TA). Members of the
genus Fusarium produce a range of chemically different phytotoxic compounds,
such as fusaric acid (FA), fumonisins (fumonisin B1, FB1), beauvericin (BEA),
enniatin (ENN), moniliformin (MON), and trichothecenes. These possess a variety
of biological activities and cause morphological, physiological, and metabolic
effects including necrosis, chlorosis, growth inhibition, wilting, and inhibition of
seed germination and effects on calli (Desjardins and Hohn 1997).
Table 12.1 summarizes the general classes of mycotoxins with their producing
fungal genera/species and chemical groups. Some of these mycotoxins are phytotoxic and others are non-phytotoxic. Mycotoxins with phytotoxic properties will be
addressed below on the basis of their producing species. This review provides
insight into characterization and evaluation of mycotoxins as phytotoxins. For each
of the diverse groups of mycotoxins, we will give examples indicating history and
fungi production with a focus on their modes of action and phytotoxic effects on
several morphological and biochemical processes.
12.2 Types of Mycotoxins
There are five mycotoxins or groups of mycotoxins that occur quite often in food:
deoxynivalenol/nivalenol, zearalenone, ochratoxin, fumonisins, and aflatoxins. The
fungi that produce mycotoxins in food fall broadly into two groups: those that
invade before harvest, commonly called field fungi, and those that occur only after
harvest, called storage fungi. There are three types of toxicogenic field fungi: plant
pathogens such as Fusarium graminearum (deoxynivalenol, nivalenol); fungi that
grow on senescent or stressed plants, such as Fusarium moniliforme (fumonisin)
and sometimes Aspergillus flavus (aflatoxin); and fungi that initially colonize the
plant before harvest and predispose the commodity to mycotoxin contamination
after harvest, such as Penicillium verrucosum (ochratoxin) and A. flavus (aflatoxin)
(Tola and Kebede 2016).
12.3 Occurrence and Toxicity of Mycotoxins
Mycotoxins are poisonous chemical compounds and secondary metabolites produced by fungus or molds. Those mycotoxins that do occur in food and/or feedstuffs
have great significance in the health of humans and livestock. Since they are produced by fungi, mycotoxins are associated with diseased or moldy crops, although
the visible mold contamination can be superficial. The effects of some foodborne
mycotoxins are acute symptoms of severe illness appearing very quickly. Other
12 Fungal Mycotoxins