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Triticeae Genomics and Genetics 2012, Vol.3, No.2, 9
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group, one would expect that there may be homoeo-
logous relationship between MQTL mapped on these
three homoeologous chromosomes. In this connection,
it is interesting to note that at least one MQTL on
chromosome 3A (MQTL2) is homoeologous to one
MQTL each on chromosome 3B (MQTL5) and chro-
mosome 3D (MQTL7). The proportional comparative
positions of these three MQTLs (MQTL2, MQTL5
and MQTL7) on the consensus map (of genetic length:
3A; 173 cM, 3B; 164 cM and 3D; 79 cM) are so close
(MQTL 2 located at 55.76% of chromosome length,
MQTL 5 at 58.78% of chromosome length and MQTL
7 at 55.32% of chromosome length) that these may
certainly be homoeo-triplicate MQTLs, if the
differences in the genetic length of these chromo-
somes is due to random insertions or deletions. This is
further substantiated by the fact that MQTL2 resulted
from condensation of QTLs for PHST and grain
colour, MQTL5 resulted from condensation of three
QTLs, one each for PHST, dormancy and grain colour,
while MQTL 7 resulted from condensation of QTLs
for PHST and dormancy. These triplicate QTLs may
therefore, represent a complex locus controlling all the
three traits (PHST, dormancy and grain colour).
Further studies may be conducted to verify this
observation. The remaining four MQTLs belonging to
the homoeologous group 3 do not show any similarity
in their position on homoeologous chromosomes on
the consensus genetic map. It is possible that the
homoeologues for these four MQTLs do occur, but
have not been identified so far. Similar homoeologous
MQTL may also be detected in other homoeologous
groups in future studies.
2.3 MQTLs for PHST versus QTLs for PHST,
dormancy and grain colour
It is known that QTL that were condensed into
meta-QTL for PHST and dormancy were detected
using different parameters including sprouting index
(SI), visually sprouted seeds (VI) and falling number
(FN) for PHST, and germination index (GI) for
dormancy. Another associated trait was grain colour,
for which no specific parameter was required. A
critical analysis would suggest that, some individual
MQTLs resulted from condensation of QTLs for the
same trait/parameter, while others resulted from
condensation of QTLs for more than one traits/
parameters. For instance, MQTL3 resulted from two
original QTLs, both for seed dormancy (Mares et al.,
2009; Kottearachchi et al., 2008), and MQTL4
resulted from three original QTLs, each for PHST
(Kulwal et al., 2004; Mohan et al., 2009; Groos et al.,
2002). This suggests that perhaps PHST and
dormancy may be controlled by at least some
independent genes, although there may be other loci
carrying pleiotropic or closely linked genes, thus
influencing both these traits (PHST and dormancy).
Such a conclusion is further substantiated by the
observation that the remaining six MQTLs (MQTL 1,
2, 5, 6, 7, 8) resulted due to condensation of QTLs for
PHST as well as those for dormancy and/or grain
colour. MQTL 1 resulted from condensation of four
QTLs including one for PHST and three for dormancy,
MQTL 2 resulted from condensation of QTLs for both
PHST and grain colour (GC), MQTL 5 resulted from
condensation of QTLs for three traits, namely PHST,
dormancy and grain colour, MQTL 6 resulted from 3
QTLs including one QTL for PHST and 2 QTLs for
dormancy, MQTL 7 was based on 5 QTL for PHST
and one for dormancy and finally MQTL8 resulted
from condensation of 7 QTLs for PHST and 4 QTLs
for dormancy. Therefore, it is obvious that in majority
of cases either QTLs for PHST and dormancy (e.g.
MQTL 1, 6, 7 and 8), or those for PHST and grain
colour were co-localized (e.g., MQTL 2), although
rarely, QTL for all the three traits were also co-
localized (e.g., MQTL 5). However, since PHS
tolerant genotypes with amber colour have been
obtained (CN19055: Hucl and Matus-Cadiz, 2002;
AUS1408: Mares, 1987; AUS26906: Zou, 1999;
Clark’s Cream: Bhatt et al., 1981), it is obvious that
QTLs for PHST and GC may be closely linked rather
than pleiotropic in nature.
2.4 An important MQTL on 4A
Since there is a solitary MQTL (MQTL 8) on
chromosome 4A, which is based on condensation of
11 original QTLs (maximum number for any MQTL),
and since it is known that no QTL/gene for red grain
colour is located on chromosome 4A, it is obvious that
this QTL is important for developing white-grained
PHS tolerant wheat genotypes. This important QTL
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