Journal of Biosciences and Medicines, 2014, 2, 68-74
Published Online March 2014 in SciRes. http://www.scirp.org/journal/jbm
http://dx.doi.org/10.4236/jbm.2014.21008
How to cite this paper: Sokoto, M.B. and Muhammad, A. (2014) Response of Rice Varieties to Water Stress in Sokoto, Su-
dan Savannah, Nigeria. Journal of Biosciences and Medicines, 2, 68-74. http://dx.doi.org/10.4236/jbm.2014.21008
Response of Rice Varieties to Water Stress in
Sokoto, Sudan Savannah, Nigeria
M. B. Sokoto*, A. Muhammad
Department of Crop Science, Faculty of Agriculture, Usmanu Danfodiyo University, Sokoto, Nigeria
Received December 2013
Abstract
Pot experiment was conducted at the Botanical Garden of the Department of Biological Science,
Usmanu Danfodiyo University, Sokoto Nigeria, during the 2013 dry season. The main objective of
this research was to determine the effect of water stress and variety on productivity of rice (Oryza
sativa) at Sokoto. The treatment consisted of water stress at three growth stages (Tillering, flow-
ering, Grain filling) and unstress (control) and three rice varieties (FARO 44, NERICA 2 and FARO
15) laid out in a Completely Randomised Design (CRD) replicated three times. The result indicated
that water stress significantly (P < 0.05) resulted to decreased in plant height, number of leaves
per plant, total biomass, harvest index and grain yield. The results indicated significant (P < 0.05)
differences among genotypes. Faro 44 differed significant from in plant height, number of leaves
per plant, total biomass, harvest index and grain yield. FARO 44 differed significantly from NERICA
2 and FARO 15 at all the parameters under study. Water is very vital as far as rice production is
concern should be applied at every stage of rice production. FARO 44 is recommended for the area
for higher yield.
Keywords
Response; Rice Varieties; Water Stress; Sudan Savannah, Nigeria
1. Introduction
Rice (Oryza sativa L.) is the most important cereal crop in the world and it is the primary source of food and cal-
ories for about half of mankind [1]. More than 75% of the annual rice supply comes from 79 million hectares of
irrigated paddy land. Irrigation is an important practice in agriculture, the competition for fresh water in the de-
velopment of urbanization, industry, leisure, and agriculture causes the decline of fresh water for irrigation [2]-
[4]. Water scarcity is a severe environmental limitation to plant productivity. Drought induced loss in crop yield
may exceeds loses from all other causes, since both the severity and duration of the stress are critical [5].
According to [6] Stress has been define as “any environmental factor capable of inducing a potentially injurious
strain in plants”. Water is a major constituent of tissue, a reagent in chemical reaction, a solvent for and mode of
translocation for metabolites and minerals within plant and is essential for cell enlargement through increasing
*
Corresponding author.

M. B. Sokoto, A. Muhammad
69
turgor pressure. With the occurrence of water deficits many of the physiological processes associated with growth
are affected and under severe deficits, death of plants may result. The effect of water stress may vary with the
variety, degree and duration of water stress and the growth stage of the rice crop. Water stress during vegetative
stage reduces plant height, tiller number and leaf area. However, the effect during this stage varies with the se-
verity of stress and age of the crop. Long duration varieties cause less yield damage than short duration varieties as
long vegetative period could help the plant to recover when water stress is relieved. Leaf expansion during
vegetative stage is very sensitive to water stress. Cell enlargement requires turgor to extend the cell wall and a
gradient in water potential to bring water into the enlarging cell. Thus water stress decreases leaf area which re-
duces the intercepted solar radiation. Rice leaves in general have a very high transpiration rate thus under high
radiation levels rice plant may suffer due to mid day wilting. Rice plant can transpire its potential rate even when
soil moisture was around field capacity.
Water stress is one of the most limiting environmental factors to plant productivity world wide and can be
caused by both soil and atmospheric water deficits. Water stress is one of the most limiting factors for plant sur-
vival since it regulates growth and development and limits plant productivity. The effect of water stress varies
with variety, degree and duration of stress and the growth of the plant [7].
The effect of water stress on yield decrease of rice is very pronounced during certain period of growth, called
the moisture sensitive periods. The most sensitive periods to water deficits are flowering and head development.
In an experiment conducted in the Philippines [8]. It has been shown that moisture stress early in the growth of
the rice reduced tillering, thereby reduced yield. When moisture stress was extended into reproductive phase,
yield loss was significant. [9] examined the effect of varying soil water regime during different growth phaseson
rice yield. They reported that the soil water stress applied any of the growth phases reduced rice grainyield,
compared to the continuous flooding irrigation. The ripening phase appeared to be most sensitive to compared to
the other phases. Soil water stress during the earlier growth phases (vegetative) appeared the production of ef-
fective tillers resulting in the reduction of grain yield, while stress during the later growth phases (reproductive)
appeared to affect the reproductive physiology by interfering with pollination, fertilization and grain filling in
the reduction of grain yield.
The objectives of this study are to examine the effects of water stress on growth and yield of three rice var i e-
ties in Sokoto.
2. Materials and Method
2.1. Experiment Site
Pot experiment was conducted during the 2013 dry season at the Botanical garden of the Department of Bio-
logical Science, Usmanu Danfordiyo University, Sokoto. Sokoto State is located between latitude 13˚01' North
and longitude 05˚15' East of about 350 m above sea level.
The area has a long dry season that is characterized by cool dry air during harmattan from November to Feb-
ruary and hot dry air during hot season from March to May. Relative humidity ranged from 26% - 39% in the
dry season. Minimum temperature ranged between 19˚C and 29˚C and maximum temperature ranged from 30 to
40˚C and, wind speed ranged between 1.8 to 5 MS−1 [(Sokoto Energy Research Center) (SERC, 2013)] (Appen-
dix 1). Soil sample was collected from 0 - 20 cm soil depth and analyzed for physic-chemical characteristics.
The soil of the experimental area is sandy, slightly acidic, low in organic carbon, total nitrogen, exchangeable
cations and available phosphorous (Appendix 2).
Treatments consisted of factorial combination of water stress at three (3) critical growth stages (Tillering,
Flowering and Grain filling) and unstress (control) and three varieties of rice (FARO 44, NERICA 2 and FARO
15), laid out in a Completely Randomized Design with three (3) Replications.
2.2. Pot Preparation
Pot was arranged according to the design layout Complete Randomized Design each pot containing 5.0 kg of the
soil which was collected from the Fadama at Kwalkwalawa near the Univer s ity. NPK 15:15:15 fertilizer was
applied at the rate of 76 kg N, 30 kg P and 30 kg K, the fertilizer was applied at basal and at 4 and 6 weeks after
planting. Three varieties of rice were sown at the rate of 10 g/pot by broadcasting method; the seedlings were
latter thinned to10 stands per pot. Weeding was done manually using hand at 2 - 3 and 5 - 6 weeks after planting.

M. B. Sokoto, A. Muhammad
70
There was no record of pest and disease attack. Harvesting involves manual cutting and collection of matured
rice panicles when the rice ripens in to a golden brown colour. Data was collected in respect of plant height,
Number of leaves per plant, biomass, harvest index and grainyield. The data collected were subjected to the
analysis of variance (ANOVA) and treatments were compared using Duncan’s New Multiple Range Test
(DNMRT ).
3. Results and Discussion
3.1. Plant Height
The effect of water stress and variety on plant height is presented on Table 1. The result indicated that water
stress had no significant (P < 0.05) effect on plant height at 3 Weeks After Planting (WAP). Water at tillering
resulted to significant (P < 0.05) reduction in plant height at 6, 9, 12 and 15 WAP. Control (unstress) is statisti-
cally (P < 0.05) similar with water stress at flowering and grain filling. The reduction in plant height was as a
result of water stress imposed at tillering stage. This is because imposing water stress resulted in law leaf water
potentials and reductions in photosynthesis; photosynthetic activity declines because of decreased stomatal
opening and the inhibition of chloroplast activity; this reduced the length of the internodes at jointing stage
which follows tillering stage. At the time when water stress was imposed at flowering and grain filling, the
jointing stage had taken place and plants have reached their maximum height, thus the effect of water stress was
ineffect ive. [10] and [11] Found significant reductions in tillers and panicles numbers as well as plant height and
grain yield when water stress was imposed at tillering stagewater stress resulted to decreased in plant height,
number of tillers per plant, total biomass and grain yield [12 ]-[14].
The effect of variety showed that at 3 WAS varieties did not differ in plant height. But Faro 44 differed sig-
nificantly with taller plants, while Wheata 4 and Nereca 2 did not differ significantly with shorter plants. The
significant differences among genotypes for plant height indicate appreciable amount of variability among the
genotype s. [15] subjected the varieties to moisture stress at different growth stages particularly during seeding
stage. They identified some promising lines had tolerance to the water stress. [16] reported varietal differences
among the cultivar for moisture stress.
Table 1. Effect of water stress and variety on plant height of rice at Sokoto.
Treatments Weeks after planting
Water Stress 3 6 9 12 15
Tillering 17.13 29.43 46.79 60.39 60.41
Flowering 17.06 33.11 51.63 68.16 68.46
Grainfilling 17.56 3202 52.09 67.43 67.63
Control 17.90 32.00 53.37 68.89 68.91
Significance * * * * *
S.E± 0.652 0.433 1.200 1.872 1.642
Variety
NERICA 2 19.31 32.03b 51.39b 67.88b 68.12b
FARO44 20.68 35.56a 55.76a 74.12a 74.36a
FARO15 19.42 31.27b 51.26b 67.12b 68.67b
Significance * * * * *
S.E± 0.564 0.375 1.039 1.621 1.422
Interaction
WXV NS NS NS NS NS
Within a treatment, mean in a column followed by the same letter(s) in superscript are not significantly different using LSD; NS = not significant, * =
significant at 5%.

M. B. Sokoto, A. Muhammad
71
3.2. Number of Tillers per Plant
The effect of water stress and variety on number of tillers per plantis is presented in Table 2. Water stress at
tillering resulted in significantly (P < 0.05) fewer number of tillers than water stress at flowering or grain filling
and control (no stress) which were statistically at par with each other. The fewer tillers recorded at tillering could
be as a result of water stress imposed at tillering because non-availability of water at tillering stage resultedin
reduction in the amount of intercepted photosynthetically active radiation (PAR). Similarly, during tillering plant
produces leaves and due to reduced growth as a result of water stress, the leaf initiation gets decreased and thus,
tends to reduce tillering. [10] and [ 11] reported that significant reductions in tillers and panicles numbers as well
as plant height and grain yield were found when water stress was imposed at tillering stage.
The effect of variety indicated that.FARO 44 differed significantly (P < 0.05) with higher number of tillers per
plant, while FARO15 and NERICA 2 did not differ significantly with fewer number of tillers plant. The signifi-
cant differences among genotypes for number of tillers indicate appreciable amount of variability among the
genotypes. [15] identified promising lines tolerance to water stress. [16] reported varietal differences among the
cultivar for moisture stress.
3.3. Number of Leaves per Plant
The effect of water stress and variety on number of leaves per plant is presented on Table 2. The result indicated
that water stress had no significant effect on number of leaves per plant at 3 Weeks After Planting (WAP). Water
at tillering resulted to significant (P < 0.05) reduction in number of leaves per plant at 6, 9, 12 and 15 WAP. The
reduction in plant height could be as a result of water stress imposed at tillering, which could result to decrease
in photosynthesis and translocation of photosynthates. The decline in leaf number is due to death and abscission
of leaves at faster rate as no new leaves were initiated during the reproductive stage. Significant reduction of
number of leaves at tillering was as a result of water stress imposed at that stage, this was because law leaf water
potential resulted in large reductions in photosynthesis, the reductions are caused both by decreases in the pho-
tosynthetic activity of a unit of leaf and in the production of new leaf surface.
Table 2. Growth and yield of three (3) rice varieties as influenced by water stress at Sokoto.
Water stress Number of
tillers/plant Number of Leaves per plant 6 WAP
Number of Leaves
per plant 9 WAP Number of Leaves per plant 12 WAP Biomass Harvest index
Grain yield
t/ha
Tillering 5.19 12.44 19.33 19.89 4.66b 23.84b 1.111b
Flowering 9.29 15.89 22.67 23.11 5.68a 15.65c 0.889c
Grain filling 9.33 15.00 22.56 23.44 5.59a 15.65c 0.889c
Control 9.33 15.33 22.67 23.67 5.72a 52.44a 3.00a
Significance * * * * * * *
SE± 0.304 0.416 0.786 0.906 0.241 9.04 0.429
Variety
NERICA 2 5.92b 14.67b 21.92b 24.75b 4.42b 28.28b 1.20b
FARO44 8.25a 16.50a 24.33a 26.75a 5.69a 57.11a 3.25a
FARO15 5.18b 14.56b 21.89b 24.83b 4.69b 26.65b 1.25b
Significance * * * * * * *
SE± 0.964 0.360 0.680 0.640 0.340 2.830 0.371
Interaction WX V NS NS NS NS NS NS NS
Within a treatment, mean in a column followed by the same letter(s) in superscript are not significantly different using LSD; NS = not significant, * =
significant at 5%.

M. B. Sokoto, A. Muhammad
72
The effect of variety showed that FARO 44 differed significantly (P < 0.05) with higher number of leaves per
plant, while FARO 15 and NERIC 2 did not differ significantly with fewer number of leaves per plant. The sig-
nificant (P < 0.05) differences among genotypes for plant height indicate appreciable amount of variability
among the genotypes. [16] reported varietal differences among the cultivar for moisture stress.
3.4. Biomass
The effect of water stress and variety on biomassis is presented on Table 2. Water stress at tillering resulted in
lower biomass than water stress at flowering and grain filling or no stress control which were statistically similar.
Lower biomass was from water stress at tillering. This could be as a result of water stress imposed at tillering
which could result to decrease in photosynthesis, translocation rate and dry matter accumulation. Similarly till-
ers per unit area, plants height, number of leaves all these contributes to biomass and all these components were
affected by water stress.
The effect of variety showed that FARO 44 differed significantly (P < 0.05) with higher biomass, while
FARO 15 and NERECA 2 did not differ significantly with lower biomass. This could be as a result of taller
plants and higher plants produced by FARO 44. The significant differences among genotypes for biomass indi-
cate appreciable amount of variability among the genotypes. [16] reported varietal differences among the culti-
var for moisture stress.
3.5. Harvest I nd ex
The effect of water stress and variety on Harvest index (HI) of threerice varieties is presented on Table 2. Water
stress at flowering and grain filling resulted in lower HI than water stress at tillering and no stress control which
are statistically similar with higher HI. Decrease in HI could be largely due to water stress which resulted to de-
crease in translocation of assimilates to the grains, which lowered grain weight and increased the empty grains.
High HI indicate the efficient translocation of assimilates towards sink. Lower HI values under water stress at
flowering and grain filling stages indicate that it was more harmful in translocation of assimilates towards the
grain s . This is in accord with that of [17] who observed highest HI well irrigated genotypes compared to that of
the genotypes which were grown under water stress condition the result indicated that water stress at flowering
and grain filling resulted in lower HI than water stress at tillering and no stress control which are statistically
similar with higher HI. Decrease in HI could be largely due to water stress which resulted to decrease in trans-
location of assimilates to the grains, which lowered grain weight and increased the empty grains. High HI indi-
cate the efficient translocation of assimilates towards sink. Lower HI values under water stress at flowering and
grain filling stages indicate that it was more harmful in translocation of assimilates towards the grains. This is in
accord with that of [17] who observed highest HI well irrigated genotypes compared to that of the genotypes
which were grown under water stress condition.
The effect of variety showed that Faro 44 differed significantly (P < 0.05) with higher harvest index, while
FARO 15 and NERICA 2 did not differ significantly with lower harvest index. The significant differences
among genotypes for harvest index indicate appreciable amount of variability among the genotypes. [16] re-
ported varietal differences among the cultivar for moisture stress.
3.6. Grain Y i e ld
The effect of water stress and variety on grain yield (t∙ha −1) of three rice varieties is presented on Table 2. Water
stress at flowering and grain filling resulted to significant (P < 0.05) reduction in grain yield. Yield reduction
due to water stress could be as a result of reduction in photosynthesis and translocation. There was a linear rela-
tionship between available water and yield, where reduction in available water limits evapotranspiration and
consequently reduced yield, as reported by several researchers [18]. [19] reported that drought stress at duration
of filling grains period with acceleration in ripening time, casing to growth period duration and filling grains de-
creased.
The effect of variety on grain yield indicated that Faro 44 differed significantly (P < 0.05) with higher grain
yield, while FARO15 and NERICA 2 did not differ significantly with lower grain yield. The significant differ-
ences among genotypes for plant height indicate appreciable amount of variability among the genotypes. [16]
reported varietal differences among the cultivar for moisture stress.

M. B. Sokoto, A. Muhammad
73
4. Conclusion
The water stress applied after tillering initiation stage is more effective on grain yield and the other characters.
FARO 44 exhibited better water stress tolerance and this variety proved the promising cultivar under water stress
conditions or water limiting area.
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M. B. Sokoto, A. Muhammad
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Appendix 1. Soil Physico-Chemical Properties of the Experimental Site during the
2013 Dry Seasons
Physical properties 2013 dry season
Sand (g∙kg−1) 701
Silt (g∙kg−1) 127
Clay (g∙kg−1) 172
Textural class Sandy loam
Chemical Properties
pH in (H2O) 1:1 ratio 6.4
Total nitrogen g∙kg−1 0.046
Organic C (g∙kg−1) 16.98
Available P (mg∙kg−1) 1.64
Exchangeable bases (C mol∙kg−1)
Ca 2.4
Mg 1.9
K 1.56
Na 0.95
CEC (C mol∙kg−1) 8.4
Appendix 2. Meteorological Data during the 2013 Dry Seasons at Sokoto
Months Mean Max Temp (˚C) Mean Min Temp (˚C) Relative Humidity (%) AVG. Wind Speed (m/s)
Ma rch 40.8 28.0 17.00 1 .8
April 42.0 29.7 28.28 2.6
May 40.8 26.3 49.08 3.8
June 39.0 24.2 18.20 1.9
Source: Sokoto Energy Research Center UDUS.