Rice Genomics and Genetics 2015, Vol.6, No.1, 1-5
3
mapping population MASARB25 × Pusa Basmati
1460 and two QTL for effective number of tillers per
plant with an R
2
value of 26.4% and 29.3%,
respectively, in the mapping population HKR47 ×
MAS26. The QTLs identified earlier were not
identified in the present study. It can be hypothesized
that there was a strong G × E interaction among
traits. It may be possible because of the small size of
the population. The co-location of QTLs inherited
from different parents as shown by DPE (Table 3)
suggest that it will be necessary to fine map the
particular region, which assist the precise introgression
of the QTLs in a marker assisted selection (MAS)
program.
QTL analysis is an unbiased investigation of the
genes affecting a particular trait which provides
information on the location of important loci for the
traits under study without any prior knowledge on
the genes involved and reveals their possible genetic
effects leading to phenotypes of interest. In the
present study, six QTL (for four traits; yield per
plant, effective number of tillers per plant, grain
weight and root length) were identified within a
region of 24.9 cM between RM8020 and RM72
markers on chromosome 8. A significant positive
correlation has also been observed between yield per
plant and effective number of tillers per plant, grain
weight and root length. It might be possible that this
24.9 cM region is contributing towards root, yield
and yield attributing traits and promoting adaptation
to aerobic cultivated conditions. This region may
facilitate marker assisted breeding to develop
aerobic adapted high yielding rice varieties. It is
quite interesting that this study led to the identification
of a number of QTL on chromosome 8 which also
possesses QTL for aroma and kernel elongation in
Basmati rice. These two QTLs (aroma and cooked
kernel elongation) are linked and present in the
vicinity of QTL identified in the present study
within 69~78.6 cM region on chromosome 8 (Jain et
al., 2004; Jain et al., 2006). It indicates that it would
be difficult to introgress these QTL promoting aerobic
adaptation in Basmati rice.
3 Materials and Methods
3.1 Plant material
Seed harvested from the F
1
plants obtained from the
cross between “HKR47” (used as female) and
“MAS26” (used as male) varieties of
indica
rice, were
used to raise F
2
population in pots during 2012 kharif
season in the net house of Department of Molecular
Biology, Biotechnology and Bioinformatics at CCS
Haryana Agricultural University, Hisar. While
“HKR47” is a low-land high yielding
indica
rice
variety unadapted to cultivation in aerobic conditions
whereas “MAS26” is an aerobic rice variety developed
at University of Agricultural Sciences, Bangalore.
3.2 Net house evaluation and trait measurements
HKR47 × MAS26 F
2
population comprising of 184
plants were sown in the pots (one plant per pot) in a
net house and raised to maturity under aerobic
cultivated conditions. Seeds were sown in pots of
12ʺ height. Vermicompost manure was added in the
soil at the time of pot filling. The pots were irrigated
with one liter of water for the first fifteen days, then
at an interval of three days up to panicle emergence
and then at an interval of two days after panicle
emergence. Yoshida nutrient solution was given to
the plants growing in pots (500 mL per pot) after an
interval of 21 and 70 days from the sowing date. The
pots were kept weed-free by manual weeding. At
physiological maturity, data was recorded on
agronomic traits, plant height in cm (PH), effective
number of tillers per plant (TN), panicle length in
cm (PL), 1,000-grain weight in g (TGW), length/breadth
ratio (L/B), and grain yield in g (YPP). Plant height
was measured from the stem base to the tip of
highest panicle (excluding awn). Fully developed
tillers bearing panicles of each plant were counted at
the time of maturity. Length of panicle was
measured from the base of panicle until the tip of the
last grain. The length and breadth of three seeds
from each plant was recorded using digital Vernier
Caliper. For grain weight determinations, 100-grain
(dehusked) samples were taken from the harvested
grains to compute 1000-grain weight. Grain yield
per plot was recorded after harvesting, threshing,
and drying to moisture content adjusted to 14%. The
data on root length (RL, cm), fresh and dry root
weight (FRW and DRW in g), root thickness (RT in
cm), and dry shoot weight (DSW in g) was recorded
and analyzed. For the measurement of root traits,
plants were removed from the pots and gently
washed. Root length was measured using a centimeter
scale. The roots and shoots were then separated by
cutting from the stem base. For fresh root weight,
