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that are resistant to diseases caused by toxigenic
Fusarium phytopathogens.”
Until the 1990s, FHB resistance breeding
relied entirely on phenotypic selection. This
approach is practical, but also resource demand-
ing and time consuming (Spanakakis 2003). In
nature the occurrence of Fusarium epidemics
depend on the local agronomic practice and
weather conditions. Therefore, in a breeding sit-
uation, phenotypic selection for resistance is
usually done in separate screening nurseries.
To make regular progress in selection, artificial
inoculation is indispensable in most situations
(Ruckenbauer et al. 2001; Dill-Macky 2003).
FHB resistance is a complex trait and not one
single, simple way of measuring FHB resistance
is practiced. The concept of resistance to initial
infection (type 1) and resistance to fungal spread
from an infected floret along the rachis (type
2) first described by Schroeder and Christensen
(1963) is still widely accepted. In addition, fur-
ther types or components of resistance to FHB
have been described (Mesterhazy 1995; Mester-
hazy et al. 1999). Specific methods for testing
genotypes for the different types of resistance
have been proposed (Dill-Macky 2003). Gener-
ally an FHB epidemic is provoked by providing
infectious material (fungal spores or mycelia)
at the proper time of infection (anthesis) and
environmental conditions (high humidity) which
stimulate the disease. For a more detailed review
on inoculation and evaluation methods, see Dill-
Macky (2003).
Breeders who included selection for improved
FHB resistance in their breeding programs
successfully developed improved cultivars for
this trait. A common observation was that short-
straw cultivars were more FHB susceptible than
tall cultivars, indicating a pleiotropic effect of
stem-shortening alleles on reducing FHB resis-
tance (Spanakais 2003). Later studies showed
that particularly the semi-dwarfing allele
Rht-
D1b
and, to a lesser extent,
Rht-B1b
appear
associated with increased FHB susceptibility
(Miedaner and Voss 2008; Voss et al. 2008; Srini-
vasachary et al. 2009). Plant height
per se
seems
to play a considerable role in this context (Yan
et al. 2011). FHB resistance was considered a
truly quantitative trait, modulated by polygenes
and environmental conditions, but the number
and chromosomal location of FHB resistance
quantitative trait loci (QTL) remained unknown
before the 1990s.
Since the early 1990s, significant research
investments have been undertaken to better
understand the inheritance of Fusarium resis-
tance in wheat in order to derive knowledge-
based and focused breeding strategies. This
research effort was inspired through the urgent
need to incorporate FHB resistance in region-
ally adapted cultivars because of startling losses
due to FHB epidemics in the 1990s (McMullen
et al. 1997; McMullen 2003; Johnson et al.
2003), and at the same time the availability of
novel molecular genotyping tools and statisti-
cal methods for genetic mapping of polygenes
(Tanksley 1993).
A comprehensive synopsis of the knowledge
on mapped QTL for FHB resistance was pro-
vided by Buerstmayr et al. (2009), who summa-
rized the results from 52 QTL-mapping studies,
9 research articles on marker-assisted selection,
and 7 articles on marker-assisted germplasm
evaluation. They illustrated the position of pub-
lished QTL in a consensus linkage map and pro-
vided extensive tables summarizing the essen-
tial information on FHB resistance QTL. In a
QTL meta-analysis, Loffler et al. (2009) used the
results from 30 mapping populations and high-
lighted 19 meta-QTL on 12 wheat chromosomes,
which were, to a large extent, in agreement with
the results from Buerstmayr et al. (2009). Liu
et al. (2009) performed a QTL meta-analysis of
FHB resistance in wheat. They grouped FHB
resistance QTL into 43 clusters on 21 wheat
chromosomes and identified 19 confirmed QTL
on 8 chromosomes. A survey of FHB resistance
QTL found in European winter wheat was pub-
lished by Holzapfel et al. (2008). QTL for FHB
resistance have been reported on all 21 wheat
chromosomes (Buerstmayr et al. 2009; L offler
et al. 2009; Liu et al. 2009).
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