Genomics-Assisted Breeding for Fusarium Head Blight Resistance in Wheat - Translational Genomics for Crop Breeding: Biotic Stress - page 54

et al. (1999), and Buerstmayr et al. (2002, 2003)
and later rediscovered in a number of studies
using Sumai-3 or related Asian lines as resis-
tance donors (see references in Buerstmayr et al.
2009; Loffler et al. 2009; Liu et al. 2009). This
QTL was designated Qfhs.ndsu-3BS (Anderson
et al. 2001). In high-resolution mapping popula-
tions segregating at Qfhs.ndsu-3BS , this locus
was fine-mapped as a single Mendelian gene
with high precision and therefore renamed Fhb1 .
Flanking markers bracketing Fhb1 within a 1.2
cM interval are now available (Liu et al. 2006;
Cuthbert et al. 2006), including the PCR marker
Umn10 , a nearly perfect PCR marker for this
resistance gene (Liu et al. 2008). It was therefore
logical that this QTL was the first candidate for
marker-assisted selection of FHB resistance in
wheat.
Del Blanco et al. (2003) evaluated 36 pheno-
typically selected hard red spring wheat breeding
lines obtained through several cycles of cross-
ing to North Dakota adapted bread wheat geno-
types and deriving their FHB resistance from
Sumai-3 using 152 microsatellites primer pairs.
Among these, two SSR loci were associated with
type 2 FHB resistance: Xgwm533 and Xgwm274 ,
both mapping to chromosome 3B. The marker
Xgwm533 explained 30% of the phenotypic vari-
ation for type 2 FHB resistance in this set of
breeding lines. A second SSR marker on the
long arm of chromosome 3B, Xgwm274 ,was
also associated with FHB resistance, but at lower
stringency.
Zhou et al. (2003) evaluated SSR markers
linked to Fhb1 in two Ning-7840 (Aurora/Anhui-
11//Sumai-3) derived segregating populations.
SSR markers in the Fhb1 genomic region were
strongly associated with type 2 FHB resis-
tance: lines with the resistant allele in this
region showed on average about half the number
of Fusarium-damaged spikelets in single-floret
inoculated trials compared to lines possessing the
alternative allele. Selection using markers linked
to Fhb1 appeared highly efficient. Despite that,
the variation in FHB severity among lines within
each QTL class was large, indicating that further

unknown QTL and environmental factors influ-
enced FHB severity in these populations.
Yang et al. (2003) performed MAS in two
doubled haploid populations descending from
crosses of Sumai-3 derivatives and the elite
Canadian spring wheat cultivar AC Foremost.
Markers near Fhb1 explained 12-36 % of the
phenotypic variation for type 2 FHB resistance.
Lines with the Sumai-3 allele at Fhb1 -linked
SSR markers had an average reduction in FHB
severity of 40% compared to a group with the
AC-Foremost alleles.
In several four-way crosses and backcrosses
using Sumai-3 as resistance donor and Australian
wheat lines as recurrent parents, lines possessing
Fhb1 , identified by SSR markers near this locus,
had a significant average reduction of around
30% type 2 FHB severity compared to lines with
the alternative alleles at this QTL (Xie et al.
2007).
Pumphrey et al. (2007) used F 3:4 head
rows from the University of Minnesota wheat-
breeding program to establish series of near-
isogenic F 3:5 lines using markers in the Fhb1
region. They generated 19 NIL pairs descend-
ing from 15 crosses. Lines possessing Fhb1
showed average reductions of 23% for type 2
disease severity ratings and 27% for infected ker-
nels in the harvested grain. The variation in the
resistance-improving effect of Fhb1 was large:
NIL pairs with and without Fhb1 differed in type
2 FHB severity from 0% to 52% (Pumphrey et al.
2007).
In breeding populations composed of 82 fam-
ilies and a total of 793 individuals, Rosyara
et al. (2009) performed linkage and association
mapping based QTL analysis in the extended
family pedigrees for the Fhb1 region. Markers
linked to Fhb1 explained 40-50% of the vari-
ation for type 2 FHB resistance, and Fhb1 was
mapped with high precision near the SSR marker
Xbarc133 , which is in full agreement with pre-
vious QTL-mapping results (Buerstmayr et al.
2009). Rosyara et al. (2008) showed that family-
based QTL mapping in breeding populations
was a very practical approach to combine-QTL