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Molecular Plant Breeding 2012, Vol.3, No.8, 80
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Figure 2 The wheat 3B crown rot QTL identified in the
resistant variety Ernie (Li et al., 2010) was remapped using a
linkage map constructed using only PCR-based markers. The
CR-associated markers are applied in validation study and have
the potential value to be used in breeding for CR resistance in
wheat
Figure 3 The barley 3H crown rot QTL identified in the resistant
variety TX9425 (Li et al., 2009) was remapped using a linkage
map constructed using only PCR-based markers. The CR-associated
markers are applied in validation study and have the potentiality
being used in breeding for CR resistance in barley
Figure 4 Comparative mapping of the chromosomal regions
conferring crown rot resistance on barley 3H and wheat 3B,
determined using only SSR markers
Note
：
The two flanking markers (in red) of the 3B CR QTL
were mapped in a chromosomal region overlapping the barley
3H CR QTL flanked by two SSR markers (in green); However,
the markers (in green) flanking the 3H QTL were not
polymorphic in wheat Ernie/Botavia population
1.3 Validation of 3H QTL
The phenotypic data for the three barley validation
populations all showed a continuous distribution
(Table 3). The microsatellite markers closely linked
with the major barley 3H CR resistance locus,
Bmac0209
and
HVM33
, were used to identify
homozygous individuals with (RR) or without (rr) the
resistant locus from the resistant parent TX9425. The
segregation ratios of the two markers fit the expected
ratio of 1:1 in all the three validation populations.
The average scores of CR severity differed among
the three populations, with the F3 population of
TX9425/DYSYH giving the lowest scores for both of
the RR (1.20) and rr (2.71) classes (Table 4), and the
F5 population of TX9425/Naso Nijo giving the
highest scores (1.74 for RR and 3.21 for rr,
respectively). The effects of the 3H locus, based on
the differences in the average severities between the
homozygous RR and rr individuals, varied from 41.7
to 55.4%, with an average of 46.7% among the three
validation populations (Table 4).