Molecular Approaches to the Study of Trichothecene Production in Fusarium Species

Fusarium is a wide spread group of toxigenic and plant pathogenic
filamentous fungi, with a record of devastating infections on many kinds of
economically important plants. Fusarium is the causative agent of Fusarium Head
Blight (FHB) or scab, ear, stem or stalk rot in economically important cereals,
especially wheat and barley, dry rot in potatoes and crown rot in banana. FHB
infection adversely affect the quality and marketability of grain by reducing yield,
discoloring and shriveling of seeds and contamination of the grain with mycotoxins
that eventually result in heavy losses of several billion dollars to wheat and barley
farmers worldwide. The importance of these fungi and their toxins in human health
cannot be underestimated.
Fusarium has been established as the causative of alimentary toxic aleukia
(ATA). Fusarium secretes a vast array of toxins that include trichothecenes,
fumonisins, zearalenone, beuvericin etc. Trichothecenes are sequiterpenoids in nature
and are classified into 4 groups. Type A trichothecenes such as T-2, Hydroxy T-2
(HT-2) and Diacetoxyscirpenol (DAS) are produced by F. sporotrichioides, F. poae,
F. equiseti and the type B trichothecenes such as deoxynivalenol (DON) synthesized
by F. culmorum, F. graminearum and Nivalenol (NIV) by F. graminearum, F. poae,
F. equiseti. Trichothecenes are significantly phytotoxic and paves the way for
Fusarial colonization of the plant and is probably important in controlling the spread
of other fungal strains. Trichothecenes are commonly reported as contaminants in
breakfast cereals or cereal products and vegetables, as they are stable under normal
cooking conditions. DON is the most prevalent among the trichothecenes in wheat
and wheat based products, followed by the toxins such as NIV, DAS and T-2.