FUSARIUM HEAD BLIGHT AND DON CONTAMINATION MANAGEMENT IN SOFT AND DURUM WHEAT CULTIVATION - Soybean and Wheat Crops: Growth, Fertilization, and Yield - page 125

F. graminearum is considered the most pathogenic and widespread agent of FHB in
wheat. Both F. graminearum and F. culmorum produce deoxynivalenol (DON, also known as
vomitoxin), a mycotoxin of the trichotecenes group, one of the most widespread mycotoxins
in cereals, which can be synthesised in the field in small grain cereals and in maize.
Trichotecenes are associated with serious mycotoxicosis in humans and animals. This group
of mycotoxins has a great impact on the health of animals and humans, due to their cytotoxic
activity and immunosuppressive effects. Their main effects—related to their concentration in
the commodity—are a reduced feed uptake, vomiting and immunosuppression (Rotter et al.,
1996; Oswald et al., 2005). Therefore, FHB and DON limits, which have been established in
many parts of the world for animal feeding and human consumption, have made the
worldwide cereal market much more selective.
2. O CCURRENCE AND E CONOMIC I MPACT
2.1. Occurrence
FHB infection and DON contaminations have been reported by the most important wheat
producers in the world, on all continents. The aetiological complexity of FHB is the main
reason for the great diffusion of this disease and its geographical and seasonal variability.
Table 1 illustrates a review of the natural occurrence of FHB and DON contamination of
wheat grain in different part of the world in recent years (from 1984 to 2007). F.
graminearum is the most prevalent species in most sites, except in England (Nicholson et al.,
1993), Norway (Kosiak et al., 2003) and Latvia (Treikale et al., 2008), where the
environmental conditions are more favourable to F. avenaceum , F. poae and F. culmorum .
Data taken in different periods in the Netherlands have shown an interesting change in
the prevalence of the Fusarium spp. In a screening conducted in 2001 and 2002, Waalwijk et
al. (2003) found F. graminearum to be the most prevalent species, a result that was in contrast
with two previous surveys conducted in the 1980s by Daamen et al. (1991) and in the early
1990s by De Nijs et al. (1996), in which F. culmorum was reported to be the predominant
agent for FHB. Waalwijk suggested some possible reasons for this change: i) the increase in
maize production ( F. graminearum is a major pathogen on maize and has the capacity to
survive on maize stubble); ii) climatic changes might favour the propagation of F.
graminearum over F. culmorum , as the former species has a higher temperature optimum; iii)
the homothallic nature of F. graminearum , which allows the production of large masses of
ascospores that can play a role in the epidemiology.
The data from the Netherlands show that FHB is a very dynamic disease, mainly due to
its aetiological complexity. It is also possible that fungi may be spread from one country to
another due to the increases in the global grain trade. However, as far as Fusarium fungi are
concerned, this risk is likely to be minimal since these phytopathogens are field rather than
storage organisms. On the other hand, there is now overwhelming evidence of global
contamination of cereals and animal feeds with trichothecenes. Trade in wheat may,
therefore, contribute to the worldwide dispersal of mycotoxins (Placinta et al., 1999).
Scab is prevalent in warm, humid regions where flowering coincides with rainy periods.
In the United States, the incidence of this disease has been increasing over the last 10 years