Rice Genomics and Genetics 2015, Vol.6, No.1, 1-5
2
million ha with an annual production of 745.7
million tonnes (FAO, 2013,
/-
browse/Q/QC/E). More than 90% of the world’s rice
is grown and consumed in Asia where 60% of the
earth’s population lives. China and India, which
account for more than one-third of global population,
produce over half of the world's rice. In India, area
under rice cultivation is 43.5 million ha with an
annual production of 159.2 million tonnes (FAO,
2013,
. India
is the largest user of groundwater in the world - if
the trend of indiscriminate exploitation continues,
over a quarter of the global total and about 60 per
cent of aquifers in India will be in a critical
condition in another 15~20 years. We need a shift
from “land productivity” without concern for water
use to “water productivity,” that is, getting the
highest yield out of every drop of water used in
agriculture. Some important questions arise here are:
Should we continue with our present rice cultivation
practices? Do we need to have a most productive
and effective water saving cultivation method? Is it
easy to breed for aerobic adapted rice varieties? In
addition to the problem of water scarcity an equally
important aspect of sustainable rice cultivation is the
availability of labor to grow rice under traditional
cultivation conditions as the rural population moves
away from farming to work in urban areas in
industry.
Improved root system is very important for
maintaining crop yields, when plants are grown in
insufficient supplies of water or nutrients. Plants
having deeper root system colonize a large soil
volume and improve the water uptake from the
lower layers where water is expected to be available;
this helps to maintain a good plant water potential
which lead to zero or small yield decline under
water limited conditions (Mumbani and Lal, 1983).
Aerobic rice refers to a cultivation system in which
rice is dry direct seeded in well-tilled leveled fields
with uniform slope under unpuddled conditions.
Aerobic rice have long and thick root system (Yadav
et al., 1997; Ling et al., 2002), erect leaves, medium
height, better water use efficiency and maintain high
biomass and harvest index under upland conditions.
In addition to reducing water use during land
preparation and limiting seepage, percolation, and
evaporation, aerobic rice had about 51% lower total
water use and 32%~88% higher water productivity,
expressed as gram of grain per kilogram of water,
than flooded rice (Bouman et al., 2005), less labor
use (Wang et al., 2002) and reduction of greenhouse
gas emission from rice field (Mandal et al., 2010).
Even if several QTL for root traits (Zhang et al.,
2001; Liu et al. 2008; Courtois et al. 2009) and grain
yield under drought stress (Bernier et al., 2007;
Venuprasad et al., 2009) have been identified,
however, identification of consistent effect QTL for
traits promoting adaptation to aerobic cultivation
may be helpful in introducing varieties with high
yield potential.
In our earlier study, 35 QTLs associated with 14
traits were mapped on chromosomes 1, 2, 5, 6, 8, 9,
and 11 in MASARB25 × Pusa Basmati 1460 and 14
QTL associated with 9 traits were mapped on
chromosomes 1, 2, 8, 9, 10, 11, and 12 in HKR47 ×
MAS26. Two QTL (qGY
8.1
and qGY
2.1
) and one
QTL (qGY
2.2
) were identified for grain yield under
aerobic conditions in the mapping populations
MASARB25 × Pusa Basmati 1460 and HKR47 ×
MAS26, respectively (Sandhu et al., 2013).
In this paper, we report the net house evaluation of
a F
2
population derived from the cross between
“HKR47” (high yielding) and “MAS26” (aerobic)
varieties of
indica
rice for yield, yield attribute
traits and root traits. F
2
population has been used
for linkage mapping of QTLs linked with traits
promoting aerobic adaptation using already-mapped
SSR markers.
1 Results
1.1 Phenotypic variation for agronomic traits
Aerobic rice cultivar, MAS26, out yielded the
lowland variety, HKR47, under dry direct-seeded
aerobic cultivation conditions. Root length, fresh &
dry root weight and root thickness were higher in
MAS26 compared to HKR47. A large variation for
plant height (52.3~100.5 cm), effective number of
tillers/plant (1~13), panicle length (17.7~27.9 cm),
grain length/breadth ratio (2.41~3.31), grain weight
(13.6~25.8 g) and yield per plant (1~26.2 g) were
observed in HKR47 × MAS26 F
2
population. Root
traits also showed wide range of variation; root
length, fresh and dry root weight and root thickness
ranged from 18.1~72.4 cm, 3.21~57.8 g, 1.17~17.1g
