Study of Water Stress Effects in Different Growth Stages on Yield and Yield Components of Different Rice (Oryza sativa L.) Cultivars
Zinolabedin Tahmasebi Sarvestani,
Seyed Ali Mohammad Modarres Sanavy
A field experiment was conducted during 2001-2003 to evaluate the
effect of water stress on the yield and yield components of four rice
cultivars commonly grown in Mazandaran province, Iran. In northern Iran
irrigated lowland rice usually experiences water deficit during the growing
season include of land preparation time, planting, tillering stage, flowering
and grain filing period. Recently drought affected 20 of 28 provinces
in Iran; with the southeastern, central and eastern parts of the country
being most severely affected. The local and improved cultivars used were
Tarom, Khazar, Fajr and Nemat. The different water stress conditions were
water stress during vegetative, flowering and grain filling stages and
well watered was the control. Water stress at vegetative stage significantly
reduced plant height of all cultivars. Water stress at flowering stage
had a greater grain yield reduction than water stress at other times.
The reduction of grain yield largely resulted from the reduction in fertile
panicle and filled grain percentage. Water deficit during vegetative,
flowering and grain filling stages reduced mean grain yield by 21, 50
and 21% on average in comparison to control respectively. The yield advantage
of two semidwarf varieties, Fajr and Nemat, were not maintained under
drought stress. Total biomass, harvest index, plant height, filled grain,
unfilled grain and 1000 grain weight were reduced under water stress in
all cultivars. Water stress at vegetative stage effectively reduced total
biomass due to decrease of photosynthesis rate and dry matter accumulation.
to cite this article:
Zinolabedin Tahmasebi Sarvestani, Hemmatollah Pirdashti, Seyed Ali Mohammad Modarres Sanavy and Hamidreza Balouchi, 2008. Study of Water Stress Effects in Different Growth Stages on Yield and Yield Components of Different Rice (Oryza sativa L.) Cultivars. Pakistan Journal of Biological Sciences, 11: 1303-1309.
Rice (Oryza sativa L.) is the staple food for more than two-third
of the world`s population (Dowling et al., 1998). Stable and high
yields of rainfed lowland rice are important for food security in many
of the subsistence farming systems in Asia (Cooper, 1999). About 7.5%
of total rice production comes from irrigated lowland production (Bouman
and Toung, 2001). It has been estimated that more than 200 million tons
of rice are lost every year due to environmental stresses, diseases and
insect pests (Herdt, 1991; Chen and Murata, 2002). Drought stress is a
major constraint for about 50% of the world production area of rice. Yield
losses from drought in lowland rice can occur when soil water contents
drop below saturation (Bouman and Toung, 2001). Rice crops are susceptible
to drought, which causes large yield losses in many Asian countries (Bouman
and Toung, 2001; Pantuwan et al., 2002a), however, some genotypes
are more drought resistance than others, out-yielding those exposed to
the same degree of water stress. The development of drought resistant
cultivars may be assisted if mechanisms of drought resistance are known.
Iran is a semi-arid country with 240 mm annual precipitation and 600,000
ha paddy field area; all of them are irrigated lowland rice with continuously
submerge irrigation regime by keeping 3-5 cm standing water all of the
growing period. Rice is the second main consumed in Iran, with wheat being
the main staple for most of the population and Capital rice consumption
per year is 36-38 kg. Two northern province near the Caspian Sea bank
with annual precipitation of 700-1000 mm covering 70-80% of paddy filed
cultivation area in Iran. Unfortunately the main parts of rainfall are
out of rice cultivation season. Irrigation dominates water use in Iran
and surface water storage has been increased by construction of numerous
multi-purpose dams and reservoirs along rivers flowing from the Zagros
and Elburz mountains. In northern Iran irrigated lowland rice usually
experiences water deficit during the growing season include of land preparation
time, planting, tillering stage, flowering and grain filing period. Recently
drought affected 20 of 28 provinces in Iran, with the southeastern, central
and eastern parts of the country being most severely affected (Reynolds,
2001). Iranian rice cultivars consist of local and improved variety so
that, local variety are low yield (less than 4 t ha-1 based
on paddy), tall plant, high quality, generally short-term maturity (less
than 90 days from transplanting to harvesting) and marketable with high
price; meanwhile, improved variety are high yield (more than 6 t ha-1
based on paddy), short plant height, mid and long-term maturity (110-130
days), medium quality and cheaper than local variety. There is three methods
for variety improvement in Iran include of: Selection; Introduction from
IRRI and breeding techniques. Water stress may occur at different growth
stages and be of varying duration and intensities, thereby affecting growth
and yield. Different reports showed that rice grain yield affected by
water stress. If water stress occurs at tillering stage, caused to reduce
number of reproductive tiller and panicle per hill (Wopereis et al.,
1996). However some experiment showed that water stress between panicle
initiation and flowering stage to cause reduce number of grain per panicle
and when water stress event at flowering and early grain filling period,
grains sterility and panicles fertility will be reduce (Boonjung and Fukai,
1993; Garrity and O` Toole, 1994). Water stress after the flowering stage
caused to reduce grain weight (Bouman and Tuong, 2001). However, it`s
showed that different varieties performance vary response to water stress,
some of them are susceptible at vegetative stage and other at flowering
and grain filling period (Pantuwan et al., 2002a). There is very
little information on drought resistance of rice genotypes in Iran used
in lowland production. This study was carried out to describe the differences
in yield and yield component of commonly grown rice cultivars when crops
were stressed at different growth stages.
MATERIALS AND METHODS
A field experiment was carried out in Rice Research Institute of
Iran-Deputy of Mazandaran Province (Amol city) located in the north of
Iran (52° 22` N, 36° 28` E and 28 masl) during 2001-2003 at the
rice cultivation season with mean temperature 16.4, 22.9, 25.9, 27.3,
25.4°C from April to September, respectively. The research field had
a loamy-silty soil and moderate climate (Table 1).
This experiment was laid out to evaluate varietal performance of four
rice cultivars in terms of yield and yield components as affected by water
stress. The experiment was designed as a split-plot, factorial in a randomized
complete block design with three replications. Main-plots were four water
stress regimes (water stress in vegetative stage, water stress in flowering
stage, water stress in grain filling stage and control or no water stress).
Subplots were 3x4 m with 0.5 m and main plots with 1 m apart. Aimed at
water stress is shortage irrigation up to 20 days for reducing saturate
water so that narrow crack will appear in the soil surface. The control
was irrigated as required to ensure and keep a 2-5 mm level of standing
water throughout crop growth. Plants in water stress treatments were grown
under favorable water conditions with supplementary surface irrigation
throughout the crop cycle while irrigation was interrupted to induce drought
stress at around vegetative, flowering and grain filling stages. Sub-plots
were four contrasting cultivars, Tarom, Khazar, Fajr and Nemat (Table
2). A mixed commercial fertilizer was applied at the rate of 92 kg
N ha-1,44 kg P ha-1 and 83 kg K ha-1;
all of phosphorous, potassium and half of nitrogen fertilizer applied
at basal and other 50% nitrogen fertilizer has applied as a top dressing
at panicle initiation. Making nursery and management for raising seedling
have done with lowland traditional wet nursery. Seedlings 30-35 days old
(4-5 leaves stage) were used for transplanting and three seedlings were
transplanted to each hill, spaced at 25x25 cm. Since, growth duration
of cultivars were different together, for synchronously of cultivars flowering,
Nemat transplanting date (as a long-term variety) was 10 days earlier
than others (April-25) and Tarom transplanting date was later than others
as a short term variety (May-5). Plant height was measured on 10 randomly
selected hills by measuring the distance from
||Soil characteristic of experimental field and weather
||Description of cultivars under experiment
the soil surface to the tip of the highest panicle within each hill.
Grain yield was determined from a harvest area of 4 m2 (64
hills) adjusting to 14% moisture content and yields refer to rough grain
yield. All plants from the harvested area were dried at 70 °C for
total dry matter determination and harvest index was calculated as grain
yield per total dry matter. Panicle number per m2 was determined
at dough stage. To estimate the fertility of panicles, five randomly sampled
panicles per plot were counted for filled and unfilled grains and the
percentage of filled grains was calculated. Data were analyzed by Analysis
of Variance (Proc Anova). The 2-year data underwent a repeated-measures
data analysis by using a combined analysis of variance across years. All
statistical tests were carried out using the Statistical Analysis System
RESULTS AND DISCUSSION
Water deficit during vegetative, flowering and grain filling stages
reduced mean grain yield by 21, 50 and 21% respectively in comparison
to control. Grain yield differed among the four cultivars. In two years,
Nemat had the largest grain yield in the control treatment. When drought
stress was imposed at the vegetative stage, the grain yield of Nemat,
Khazar and Fajr were significantly reduced. Nemat had the highest reduction
(25%), while Tarom had only a slight reduction (14.5%). Bouman and Toung
(2001) showed that different cultivars might have different responses
to the same drought stress timing and intensity. Compared to the well-watered
conditions, panicle number was only slightly reduced in Tarom (Table
3). Total biomass, harvest index, plant height, filled
||Grain yield and plant parameters of four rice cultivars
grown under four water stress treatments in north of Iran
|A: Common letter(s) within the column do not differ
significantly at 5% level of significance analyzed by DMRT, B: W0
Control; W1: Water stress at vegetative stage; W2: Water stress at
flowering stage; W3: Water stress at grain filling stage, C: Common
letter(s) within the row do not differ significantly at 5% level of
significance analyzed by DMRT
grain, unfilled grain and 1000 grain weight were reduced under water
stress in all cultivars. Water stress at vegetative stage effectively
reduced total biomass due to decrease of photosynthesis rate and dry matter
accumulation (Table 3).
The combine analysis of variance showed that the effect of year on yield
is significant and yield at second year is more than first year due to
increase number of tillers and harvest index at second year (Table
4). There is significant interaction between water stress and kind
of varieties (1% level-Duncan test) so that cultivar of Nemat had a highest
yield and total biomass at control treatment and cultivars of Tarom and
Khazar had a lowest yield at treatment of water stress at flowering stage
Rahman et al. (2002) reported that plant height, tiller number,
panicle number, panicle length, number of filled grains per panicle, 1000-grain
weight, harvest index (HI), total dry matter (TDM) and yield were decreased
with stress. Grain yield was reduced dramatically in all cultivars with
drought starting at panicle initiation or at flowering. Water stress at
flowering reduced grain yield more than other water stress treatments.
The reduction in yield largely resulted from the reduction in fertile
panicle number and filled grain percentage. Fukai et al. (1999)
reported that maintenance of leaf water potential just prior to flowering
is associated with higher panicle water potential, reduced delay in flowering
time and reduced spikelet sterility and hence contributes to higher yield.
On the other hands, yield losses from the normal level due to water stress
are useful in assessing drought resistance. The different variety has
differently drought resistance mechanism, for a variety, which is also
different, at the different stages. However, the complex drought resistance
occurs at any growth stage in crop, with the different response and the
different mechanism to drought tolerance (Na et al., 2007). Some
researcher reported that grain yield could be drastically reduced (about
60%) if drought occurs during flowering time (Boonjung and Fukai, 1996).
Pantuwan et al. (2002b) reported that drought stress that developed
prior to flowering generally delayed the time of flowering of genotypes
and the delay in flowering was negatively associated with grain yield,
fertile panicle percentage and filled grain percentage. Genotypes with
a longer delay in flowering time had extracted more water during the early
drought period and as a consequence, had higher water deficits. They were
consistently associated with a larger yield reduction under drought. Castillo
et al. (1992) reported that draining rice fields at either vegetative
or reproductive phases caused significant yield loss. Evaluating the effect
of different durations of water stress at various growth stages showed
that water stress at any stage would reduce yield (Salam et al.,
2001; IRRI, 2002). However, the duration of these stresses was more closely
related to yield reduction than to stage at which the stress occurred.
Islam et al. (1994b) observed that yield losses resulting from
water deficit are particularly severe when drought strikes at booting
Plant height was significantly affected by water stress at booting, flowering
and grain filling stage (Table 3) over the control. This
result agrees with Islam et al. (1994b), who found that moisture
stress reduced plant height under 20% soil saturation at booting and flowering
stages. Similar result has also been reported by Islam (1999). The decrease
in height might be either due to inhibition of length of cells or cell
division by water deficits.
Water stress during vegetative stage reduced tiller number, while stress
at the reproductive and grain-filling stage reduced grain number and weight.
Rahman et al. (2002) also reported that the number of tillers per
hill was decreased significantly under moisture stress at different growth
stages except that at flowering stage. This agreed with Islam et al.
(1994a). Bouman and Toung (2001) found that drought before or during tillering
reduces the number of tillers and panicle per hill. When late season drought
was the main cause of low yield, late-maturity cultivars (such as Nemat)
were not suitable as panicle development was severely impaired.
||The combine analysis of variance on grain yield and
plant parameters of different rice cultivars under water stress treatments
|*Significant different at 0.05 level (Duncan
test); **Significant different at 0.01 level (Duncan test); ns: Not
|| Interaction effects between water stress treatments
and rice cultivars on the grain yield and plant parameters
|Common letter(s) within the column do not differ significantly
at 5% level of significance analyzed by DMRT, W0: Control; W1: Water
stress at vegetative stage; W2: Water stress at flowering stage; W3:
Water stress at grain filling period
Total grain number per panicle was drastically reduced when drought stress
occurred at flowering. This reflected the reduced crop growth due to drought
during flowering. Rahman et al. (2002) and Islam et al.
(1994a) also showed that the number of filled grains per panicle decreased
significantly with the moisture stress at booting, flowering and grains
filling stages compared with control. The proportion of unfilled grain
in the drought stress at flowering stage was 46% compared with 22% in
well-watered (control) conditions.
The 1000-grain weight in the drought stress at grain filling stage was
17% smaller than control. Thus, the yield reduction in drought stress
at flowering stage mostly resulted from reduction in total grain number
per panicle (increase in unfilled grain and a greatly decreased proportion
of filled grain) and 1000-grain weight respectively. Similar results on
1000-grain weight under water stress at booting and flowering stages had
been showed by Islam (1999) and Islam et al. (1994b). Stress during
different growth stages might decrease translocation of assimilates to
the grains, which lowered grain weight and increased the empty grains.
HI values indicate the efficient translocation of assimilates towards
sink. Lower HI values under stress at booting and flowering stages indicate
that it was more harmful in translocation of assimilates towards the grains
over grains filling stage (Rahman et al., 2002).
It has been argued that under severe drought stress, when yields are
reduced to below 50% of those under favorable conditions the relationship
between yield under favorable and stress conditions break down (Ceccarelli
and Grando, 1991). Results of this experiment suggest that genotypes had
no capability in expressing their genetic yield potential under these
conditions. It appears that the yield advantage observed under favorable
conditions of semi-dwarf cultivars (Fajr and Nemat) which required less
assimilate for vegetative organs was not maintained under water-limiting
The results also suggest that Tarom is drought-tolerant and is able to
retain green leaves longer than other cultivars under drought conditions.
Retention of green leaves in seedlings under drought conditions has been
used as a selection criterion for drought resistance (De Datta et al.,
1988). Alternatively, cultivars with green leaf retention may process
dehydration-tolerance mechanism, which allow the plants to maintain metabolic
activity, despite low leaf water potential, for example, as a result of
high osmotic adjustment (Fukai and Cooper, 1995). Other experiment also
confirmed a positive relationship between green-leaf retention and grain
yield among 35 lines (Henderson et al., 1995). From the above results
it can be concluded that cultivars required for Iranian conditions, where
frequent drought develops, are those with appropriate phenological development
to escape late drought and an ability to maintain growth during drought
that may develop late in the season. Consideration of these characters
in plant-breeding programs should increase the efficiency of plant improvement
in the region.
This study was carried out within the Ph.D project funded by the
Tarbiat Modares University and Rice Research Institute of Iran-Deputy
of Mazandaran (Amol) that supervised by Dr. Z. Tahmasebi Sarvestani. We
also gratefully thank the assistance of Dr. H. Pirdashti and M. Rahimi
on data collection.
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