Rice Genomics and Genetics 2015, Vol.6, No.1, 1-5
3
and 1.77~5.5 cm, respectively (Table 1; Figure 1).
Compared to the aerobic rice parental variety
MAS26 (RL-51.7 cm, DRW-7.48 g), 88 plants had
greater root length (51.8~72.4 cm) and 70 plants had
greater dry root weight (7.53~17.1 g).
1.2 Genetic analysis
Out of 803 SSR markers widely distributed on 12
rice chromosomes, a total of 125 (about 16%)
polymorphic SSR markers were used for the F
2
population genotyping. A DNA fingerprint database
of selected 94 HKR47 × MAS26 F
2
plants was
prepared using 125 SSR markers. On an average,
50.2 % alleles were from MAS26 and 49.8 % alleles
were from HKR47 in all 94 F
2
plants.
To
demonstrate the genetic relationship among the F
2
plants and parental rice varieties, allelic diversity
data was used for cluster tree analysis, NTSYS-pc.
The parental rice varieties HKR47 and MAS26 had
low similarity coefficient and bifurcate at coefficient
value of 0.49. All the 94 F
2
plants did not cluster
into major groups but showed more similarity to
MAS26. Two dimensional PCA scaling exhibited
that two parental genotypes were quiet distinct
whereas 94 F
2
plants interspersed between the two
parental lines with distribution of some plants
towards MAS26 (Table 2; Figure 2; Figure 3).
A total of six QTL associated with four traits (Table
3; Figure 4; Figure 5) were detected. Three QTL for
effective number of tillers per plant (qTN
8.1,
qTN
8.2
and
qTN
8.3
at map positions 36.0, 55.2, 60.9 cM,
respectively), one for thousand grain weight
(qTGW
8.1
;59.1 cM), one for grain yield per plant
(qYPP
8.1
;60.1 cM) and one for root length (qRL
8.1
,
43.7 cM) were identified. All the six QTL were
mapped on chromosome 8 within a region of 24.9
cM (36~60.9 cM) (Figure 4; Figure 5). QTL qYPP
8.1
with RM72 being the peak marker with an R
2
value
of 20.2% and qRL
8.1
with RM8243 being the peak
marker with an R
2
value of 13.7% were identified
for grain yield and root length under aerobic
cultivated conditions, respectively. qYPP
8.1
had
maximum LOD score of 5.06. RM8020 and RM72
showed significant association with effective
number of tillers/plant and RM8243 with root length.
The QTL qTN
8.1,
qTN
8.2,
qTN
8.3,
qTGW
8.1,
qYPP
8.1
and qRL
8.1
accounted for 16.1, 21.0, 17.3, 27.4, 20.2
and 13.7 % phenotypic variation, respectively. Of
the six QTL identified, one QTL (qRL
8.1
) with an
additive effect of 3.9 was from MAS26, the
remaining five QTL were from HKR47.
2 Discussion
Groundwater is the primary source for irrigation, but
overexploitation has resulted in a rapid decline of
groundwater levels (Zhang et al., 2003). To tackle
this situation, it has become essential to develop
alternate ways of rice cultivation that require less
water with no reduction in grain yield and quality.
Several strategies are being pursued, including the
development of water-efficient aerobic rice system,
to reduce water requirement for rice cultivation
including aerobic rice (Bouman, 2002).
Root system is considered as one of the important
physiological parameter to struggle against the water
scarce conditions. Under low-moisture stress, root
characters are considered to be a vital component to
Table 1 Mean and range for various agronomic and root traits in HKR47 x MAS26 F
2
population under net house conditions
Traits
HKR47
MAS26
HKR47×MAS26 F
2
population
Mean
Range
Plant height (cm)
83.7±0.38
71.2±0.25
76.3±0.93
52.3~100.5
Effective no of tillers/plant
7±0.43
10±0.49
6.86±0.23
1~13
Panicle length (cm)
21.2±0.18
19.2±0.37
23.1±0.18
17.7~27.9
Length/Breadth ratio
2.96±0.25
3.23±0.09
2.85±0.02
2.41~3.31
1000 grain weight (g)
16.8±0.17
19.8±0.27
21.5±0.22
13.6~25.8
Yield per plant (g)
7.42±0.31
8.34±0.41
11.0±0.60
1~26.2
Root length (cm)
35.3±0.45
51.7±0.61
50.0±1.00
18.1~72.4
Fresh root weight (g)
18.4±0.35
22.1±0.36
23.9±1.13
3.21~57.8
Dry root weight (g)
5.47±0.36
7.48±0.11
6.63±0.29
1.17~17.1
Dry shoot weight (g)
11.0±0.70
20.7±0.58
18.3±0.57
6.7~39.0
Root thickness (cm)
3.17±0.04
3.69±0.13
3.61±0.11
1.77~5.5
