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Triticeae Genomics and Genetics 2012, Vol.3, No.2, 9
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QTLs. Altogether, 30 Studies on QTL analysis for
PHST have so far been conducted and ~165 QTLs,
spread over all the 21 chromosomes, have been
reported (see Mohan et al., 2009 for details). These
QTLs include both major and minor QTLs. However,
the QTLs located on chromosomes of homoeologous
group 3 (3A, 3B and 3D) and chromosome 4A are
considered to be relatively more important (Flintham
and Gale, 1996; Bailey et al., 1999; Zanetti et al.,
2000; Warner et al., 2000; Watanabe and Ikebata, 2000;
Kato et al 2001; Flintham et al., 2002; Himi et al.,
2002; Gale et al., 2002; Osa et al., 2003; Kulwal et al.,
2004; 2011; Mori et al., 2005; Mohan et al., 2009).
The earlier QTL studies on PHST largely involved the
use of a number of bi-parental mapping populations,
some of them grown each in more than one environ-
ments (for a review, see Mohan et al., 2009; Kulwal et
al., 2011). It is also known that the identification of a
QTL depends on the genetic background, so that often
some of the minor QTLs identified in one genetic
background may escape detection in another genetic
background, even when the mapping populations are
grown under similar experimental conditions (Mares
et al., 2005). Further, the use of different parental
combinations and/or different environments often
resulted in identification of partly or wholly non-
overlapping sets of QTLs on the same individual
chromosomes (Rong et al., 2007). It may, therefore, be
necessary to know whether the QTL for PHST and
associated traits (e.g. grain colour) identified in a
specific genomic region in one study correspond to
those detected in the same genomic region in other
studies. This issue can be resolved through meta-QTL
analysis (Goffinet and Gerber, 2000), which combines
results from several independent studies and allows us
to estimate the number of real and stable QTLs for
each linkage group separately.
Meta-QTL analysis in wheat has been successfully
utilized to detect real QTLs for several specific
individual traits including ear emergence (Hanocq et
al., 2007; Griffiths et al., 2009), resistance against
Fusarium
head blight (Haberle et al., 2009; Loffler et
al., 2009), plant height (Griffiths et al., 2012), grain
dietary fiber content (Quraishi et al., 2010), seed size
and seed shape (Gegas et al., 2010) and for yield
contributing traits (Zhang et al., 2010). Meta-QTL
analysis has also been successfully conducted in
several other crops like maize (Chardon et al., 2004;
Truntzler et al., 2010; Hao et al., 2010; Li et al., 2011;
Wang et al., 2006; Coque et al., 2008), cotton (Rong et
al., 2007), rice (Ballini et al., 2008; Norton et al., 2008;
Khowaja et al., 2009), rapeseed (Shi et al., 2009),
potato (Danan et al., 2011), cocoa (Lanaud et al.,
2009), soybean (Guo et al., 2006; Sun et al., 2012) and
apricot (Marandel et al., 2009).
In the present study, meta-QTL analysis was carried
out for PHST and dormancy in common wheat for the
first time. For this purpose as many as 30 studies
reporting as many as ~165 QTLs for PHST spread
over all the 21 wheat chromosomes were available.
While selecting the chromosomes and reported QTLs
to be used for meta-QTL analysis, only those
chromosomes were selected which had at least 10 and
up to an optimum of 40 QTLs (Arcade et al., 2004).
Using this criterion, only 24 of 30 studies reporting 64
QTLs spread over only four chromosomes (3A, 3B,
3D and 4A) were found suitable to be included in the
present study. The results of the study, where the
above 64 QTLs for PHST/dormancy could be assigned
to 8 meta-QTLs are reported in this communication.
1 Results
1.1 Bibliography search involving QTL analysis for
PHST
A bibliography search for QTL studies on PHST and
dormancy in common wheat was first conducted. In
30 studies involving QTL analysis for PHST in
bread wheat, 35 mapping populations were used,
leading to detection of as many as ~165 QTLs, which
included QTLs for the two related traits PHST and
dormancy that were estimated using a variety of
different parameters. When ~165 QTLs (spread over
21 chromosomes) were arranged in 7 homoeologous
groups and 3 genomes, significant differences were
observed not only among different homoeologous
groups, but also among chromosomes within a group
(Figure 1). Group 3 carried the largest number of
QTLs (32.31%), followed in order by group 4
(26.21%), group 2 (14.00%), group 5 (8.53%), group
1 (7.93%), group 7 (6.75%) and group 6 (4.26%).
Approximately 43% of the QTLs were mapped on A
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