FUSARIUM HEAD BLIGHT AND DON CONTAMINATION MANAGEMENT IN SOFT AND DURUM WHEAT CULTIVATION - Soybean and Wheat Crops: Growth, Fertilization, and Yield - page 140

This may be accounted for in two ways: first, it is related to the density of the residues
left by the preceding crop, second, the nature of the preceding crop can affect the composition
of the pathogen complex throughout the following year.
As clearly reported in the literature, limited soil tillage or no-till increase the frequency of
head blight, whereas deep tillage, such us ploughing, decreases it (Teich, 1989; McMullen et
al., 1997; Miller et al., 1998; Krebs et al., 2000; Maiorano et al., 2008), because it reduces the
density of the residues on the surface of the soil and helps to decrease the production of
inoculum (Teich and Hamilton, 1985) and the quantity of spores available for dispersal
(Bateman et al., 1998).
The general effect of tillage practices that enhance Fusarium infection is highly variable:
in experiments conducted in Italy, direct sowing after maize increased the DON concentration
in wheat grains by a factor of 6.5 on average in all conditions. This effect was much smaller
when direct sowing was applied after wheat or other crops (Teich and Hamilton, 1985; Dill-
Macky and Jones, 2000). In general, the data presented clearly show that the tillage system is
less important than the influence of the preceding crop and the susceptibility of the wheat
cultivar. Furthermore, the relative importance of tillage practices for a low DON
concentration in wheat grain is closely related to the level of FHB pressure: under highly
infectious conditions, for example with grain maize as the previous crop, a highly susceptible
cultivar and abundant rainfall during anthesis, minimum tillage or no-tillage could result in a
considerably increased DON concentration.
4.2. Cultivar Susceptibility
Among the other factors examined in the several studies, the cultivation of a susceptible
cultivar showed a clearly higher DON contamination compared to a moderately resistant one.
With the exception of the experiment conducted in North Italy in 2002-2003 (Blandino et al.,
2006), in all the other works, the use of a more susceptible variety increased the content of
this mycotoxin in wheat grain by a factor of 4.6. These results, in each situation, reported a
comparison between a moderately resistant and a susceptible variety. It is assumed that if
wheat cultivars with an intermediate Fusarium rating instead of a moderately resistant and
susceptible or highly susceptible rating are tested, a considerable decrease of the varietal
effect could be expected. Furthermore, all the wheat cultivars used in these experiments were
commercial and commonly present on the farm fields. This means that the choice of the less
susceptible cultivars available on the markets is a key tool that both the farmer and end user
could apply to reduce the risk of high DON content.
At present, no durable, fully FHB-resistant wheat cultivars exist, therefore control relies
on the use of cultivars with partial resistance (Mesterhazy, 2002), but in recent studies by
Mesterhazy et al. (2005) and Tóth et al. (2008), the wheat varieties that are more resistant to
FHB were shown to reduce DON production to almost zero.
The development of FHB resistant varieties is one of the main goals of numerous
breeding programmes across the world (Yuen and Schoneweis, 2007).
Five types of varietal resistance are currently know: they affect the penetration of the
fungus into the plant (type I) (Schroeder and Christensen, 1963), the infection kinetics, with
resistance to colonisation within the ear (type II) (Schroeder and Christensen, 1963), the
degradation of the mycotoxins (type III) (Miller and Young, 1985; Miller et al., 1985), the