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Molecular Plant Breeding 2012, Vol.3, No.8, 80
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90
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(Rite grow kwik pots, www.Gardencityplastics.com,
Australia) containing autoclaved potting mix. Three
replicates, each containing 15 seedlings in five
punnets arranged in a randomised block design, were
used. Thirty punnets were placed in each plastic
seedling tray for easy handling. After planting, the
seedling trays were incubated for 24 h in a humid
chamber and then transferred to a glasshouse with
25/15 (±5)
℃
day/night temperature and 60/80 (±10)%
day/night relative humidity (RH). The seedlings were
watered only when wilt symptoms appeared. CR
severity was assessed at 35 days after inoculation with
a 0–5 scale, according to Li et al (2008).
3.4 Linkage and data analysis
Linkage analysis was conducted using JoinMap 4.0 as
described by Li et al (2008). A new linkage map were
generated for both of the 3H and 3B QTL region, and
in order to relocate the CR QTLs based on new
linkage maps, a QTL analysis based on same
phenotypic data as in the previous studies (Li et al.,
2009; 2010) was applied in both of the wheat and
barley DH populations using MapQTL 5.0 as
described by Li et al (2009). For QTL validation,
various numbers of progeny lines were randomly
selected from each of the four wheat and three barley
validation populations (Table 1; Table 2), and were
assessed for CR reaction twice at same condition, one
in the controlled environment facility (CEF) and the
other in the glasshouses. For each validation population,
two replicates, each consisting of 10 individual plants
for each line, were used in each screening trial. The
average values of CR severity of the 10 plants in each
replicate were used in further statistical analyses.
All statistical analyses were performed using GenStat
for Windows, 12
th
edition (copyright Lawes Agricultural
Trust, Rothamsted Experimental Station, UK).
Homogeneity of variance was tested using Bartlett’s
test to determine whether the data could be combined
across replicates for further analyses. An analysis of
variance was used to detect significant genetic
effects for CR severities. Within each trial, the
following mixed-effects model was used: Yij=µ+ri+gj+
wij. Where: Yij=observation on the jth genotype in the
ith replication; µ=general mean; ri=effect due to ith
replication; gj=effect due to the jth genotype;
wij=error or genotype by replication interaction,
where genotype was treated as a fixed effect and that
of replicates as random. A general mean across the
two trials was calculated for each line and used to
analyse the effect of related CR QTL in different
populations. Based on the presence or absence of
marker alleles from the resistant parents Ernie and
TX9425, the lines from each of the populations
were grouped into two classes. The difference in CR
severity between the two groups within each of the
populations was used for measuring the QTL effects.
Authors' Contributions
HBL is the executor of experimental research in this study and
took responsibility to make the experimental design, data analysis,
paper writing and revising; MXZ and CJL are supervisors of
the project and provide the necessary facilities for the research
to be performed.
Acknowledgments
The study was carried out at the Laboratory and Glasshouse
Facility of Australian CSIRO Plant Industry, St Lucia,
QLD 4067, Australia. The Research was Fund by Australian
Grains Research & Development Corporation.
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