Agriculture Reference
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consequences of infection, with tolerance to high DON concentrations (type IV) (Wang and
Miller, 1988) and the resistance to grain infection, with differences in yield despite similar
levels of attack (type V) (Mesterházy, 1995).
Type I and II resistances have been associated with certain morphological characteristics
of wheat cultivars. Hilton et al., (1999) observed a significant negative relationship between
plant height and resistance to FHB. The earliest variety seems to accumulate more
deoxynivalenol that the late-flowering varieties (Jenny et al., 2000), probably due to a greater
coincidence of the phase of maximum susceptibility in plants with the period most favourable
for spore dispersion.
Such observations have been supported by genetic mapping of the quantitative trait loci
(QTL), where the QTLs of the plant morphological traits, such as plant height and heading
date, coincide with the QTLs of lower FHB severity and DON concentration (Zhu et al.,
1999; Ma et al., 2000).
Several research groups have identified molecular markers linked to QTLs associated
with various aspects of resistance (Buerstmayr et al., 2002; Buerstmayr et al., 2003). The
most common sources of genetic resistance are derived from the Chinese variety (Zhang et
al., 2004; Yang et al., 2005; Yu et al., 2008).
As far as the most recent employment of genetic engineering is concerned, Anand et al.
(2003) produced transgenic wheat lines, expressing chitinase and ß-1,3-glucanase genes, that
provided moderate resistance to FHB in greenhouse trials. In addition, transgenic wheat
expressing the F. sporotrichioides Tri101 gene, which encodes a protein that detoxifies the
trichothecene mycotoxins produced by F. graminearum , conferred partial protection against
the spread of FHB in infected spikes (Okubara et al., 2002).
Combining all the desired agronomic characters, plus resistance to other important
disease and insects, with a high degree of resistance to FHB is still a major challenge. The
successes in enhancing resistance to FHB and DON contamination in cereals using
conventional breeding, molecular markers and through transgenic approaches have been
thoroughly discussed in several reviews (Dahleen et al., 2001; Kolb et al., 2001; Ruckenbauer
et al., 2001; Hollins et al., 2003; Miedaner et al., 2003; Bai and Shaner, 2004; Champeil et al.,
2004a; Snijders, 2004).
4.3. Fungicide Application
Adapting the crop sequence, incorporating the previous crop residues and using a
resistant cultivar are precautionary measures to control FHB infection that must be taken at
the beginning of wheat cultivation. During crop growth, a fungicide application may be
applied at anthesis to diminish DON formation (Pirgozliev et al., 2003).
Although several studies have demonstrated that good levels of control can be achieved
with fungicides in in vitro experiments (Matthies et al., 1999; Ramirez et al., 2004;
Mullenborn et al., 2008) or in trials in which wheat is artificially inoculated (Boyacoglu et al.,
1992; Mielke and Weinert, 1996; Matthies and Buchenauer, 2000; Mesterhazy et al., 2003;
Haidukowski et al., 2005), the situation under natural infection condition is less clear. In the
field, there is conflicting evidence as to the ability of fungicides to reduce FHB and to reduce
DON contamination, due to the complex interaction between fungicide, mycotoxin
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