Assessing the yield and its relationship with some of
the physiologic traits in bread wheat cultivars under
terminal drought stress
Alireza Anvari*, Hossein Shahbazi and Aliakbar Imani
Department of Agronomy, Ardabil Branch, Islamic Azad University, Ardabil, Iran
ABSTRACT
Climatic factors uctuations are among the reasons for yield change in crops during various seasons and in different
locations. Grains provide 70 percent of the food for humans and these plants are considered as the main basis for
human nutrition and survival. In order to assess the yield and study its relationship with some physiologic traits in
bread wheat cultivars under terminal drought stress, an experiment in the form of randomized complete block design
with three replications was carried out during 2015-2016 crop year in Ardabil IAU Research Farm (5 km west of Arda-
bil). ANOVA results suggested that there was a signi cant difference among the studied bread wheat cultivars based
on all traits, except for photochemical ef ciency of photosystem II (FV/Fm). Results from data mean comparison
indicated that the cultivar of Pishtaz had the highest yield and cultivars of Rasad, Soissons and Seri 82 had the best
yield after cultivar of Pishtaz. Also, the lowest yield was related to cultivars of Soltan-95 and Kenya-2002. Addition-
ally, results showed that in most physiologic traits, cultivar of Seri 82 had the highest values.
KEY WORDS: TERMINAL DROUGHT STRESS, PHYSIOLOGIC TRAITS, GRAIN YIELD, WHEAT
293
ARTICLE INFORMATION:
*Corresponding Author:
Received 27
th
Dec, 2016
Accepted after revision 2
nd
March, 2017
BBRC Print ISSN: 0974-6455
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Biosci. Biotech. Res. Comm. Special Issue No 1:293-297 (2017)
INTRODUCTION
Population growth phenomenon in developing coun-
tries and high variety of foodstuff and its high con-
sumption in developed countries have led an unprec-
edented increase in demand for foodstuff in the world.
(Akhavan, 2006) Grains provide 70 percent of the food
for humans and these plants are considered as the main
basis for human nutrition and survival. (Emam, 2007)
Climatic factors uctuations are among the reasons for
yield change in crops during various seasons and in dif-
ferent locations which lead to complexity in optimiza-
tion and reaching these goals. (De keeijer, 2003) Plant
growth is one of the most complex and most sensitive
life phenomena regarding environmental parameters
which is the re ection of the plant’s response to the
294 ASSESSING THE YIELD AND ITS RELATIONSHIP WITH SOME OF THE PHYSIOLOGIC TRAITS BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS
Anvari, Shahbazi and Imani
Table 1. Analysis of variance the traits in different cultivars of wheat
S.O.V DF
Mean Square
Leaf
Chlorophyll
Rate
Leaf
Stomatal
Conductance
photochemical
ef ciency of
photosystem II
(FV/Fm)
Relative
Water
Content
Water
Loss from
Separated
Leaf
Biologic
Yield
Harvest
Index
Grain
Yield
Replication 2 151.01 626.69 1.58 28.49 0.08 1.55 10.80 0.16
Treatment 5 147.85** 2692.35* 3.06 ns 121.91* 211.60** 10.27* 35.99* 0.82**
Error 10 15.84 589.11 1.58 33.75 23.54 2.002 10.66 0.13
C.V % 12.28 15.40 1.63 6.67 9.77 10.54 18.97 15.18
* and ** respectively signi cant 5% and 1%
environmental changes. Decrease in growth under
unsuitable environmental conditions is attributed to the
disconnect between plant yields. Hence, growth spe-
ci cally requires proper relationship between metabolic
processes in various parts. (Brevedan and Egli, 2003) In
Araus et al. (1998) study, the impact of drought stress
was signi cant on F
m
and F
0
parameters in consecutive
measurements and except for the rst measurement,
it led to increase in them in all parameters. However,
in Paknejad and Nasri (2007) study, F
m
and F
0
param-
eters were not affected by the drought stress. Although
in most studies, ef ciency of photosystem II decreases
due to the drought stress, in Havaux (1999) photosys-
tem II was resistant against drought stress. These results
are approved in other studies, too. (Živ
c
ˇ ák et al., 2008;
Christen et al., 2007) According to Živ
c
ˇ ák et al. (2008),
orescence parameters are suitable for studying photo-
synthesis ef ciency in initial stages of drought emer-
gence and after the initial stages of drought, in which
the limitation of photosynthesis emerges due to the
closure of stomata, orescence parameters could not be
used.
Results from Mahmudiyan et al. (2011) suggested that
moisture regime has had signi cant impact on traits of
stomatal conductance, grain yield, harvest index, grain
production rate and grain weight per ear. There was a
signi cant difference between cultivars and lines of this
study based on most physiologic traits. The main objec-
tive in this research was to study the impact of physio-
logic traits on wheat cultivars yield under drought stress.
METHODOLOGY
This experiment was carried out in the form of rand-
omized complete block design with three replications
during 2015-2016 crop year in Ardabil IAU Research
Farm (5 km west of Ardabil). The region climate is Semi-
arid and cold and the temperature during winter is usu-
ally subzero. The altitude of this location is 1350 m
above sea level and its latitude and longitude are 38.15
N and 48.2 E, respectively. The experienced treatments
included 6 various bread wheat cultivars (Rasad, Pishtaz,
Kenya-2002, Soltan-95, Soissons and Seri 82). Tillage
operation including moldboard plowing, disc, leveler,
and furrow, were carried out on the fallow land. In each
plot, six lines with a distance of 20 cm were formed and
harvested with a length of six meters and seed density of
450 seeds per square meters. The area of each plot was
7.2 square meters and the harvested area was six meters
through omitting half a meter from the beginning and
the end of each plot in order to exclude the effect of mar-
gin. After the bushes grew up and reached the owering
stage, in order to apply the stress and prevent reaching
rain, rain exclusion shelter was used. By the beginning
of the stress, measuring the uorescence of chlorophyll,
chlorophyll content of leaves, relative water content and
stomatal conductance was conducted after pollination
stage. Ultimately, after reaching physiological maturity,
the grain yield of 1 square meters was calculated.
RESULTS AND DISCUSSION
ANOVA results suggested that there was a signi cant
difference between the studied wheat cultivars based on
traits of leaf chlorophyll rate, water loss from separated
leaf and grain yield at one percent probability level,
and based on traits of leaf stomatal conductance, rela-
tive water content, harvest index and biologic yield at
ve percent probability level. Also, results indicated that
there was no signi cant difference between the culti-
vars based on photochemical ef ciency of photosystem
II (FV/Fm) (Table 1).
Bakhshande et al. (2006) showed that there was a sig-
ni cant difference between the studied genotypes based
on the traits of the harvest index and biologic yield
at 5%. Amini (2003) reported a signi cant difference
between the studied genotypes based on the traits of the
number of days to heading, bush height, maturity time,
number of seeds per ear, thousand kernel weight and
grain yield at 1%. ‘Abdoli et al. (2013) reported there was
BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS ASSESSING THE YIELD AND ITS RELATIONSHIP WITH SOME OF THE PHYSIOLOGIC TRAITS 295
Anvari, Shahbazi and Imani
Table 2. Mean comparison of genotypes for the studied traits
Genotype
Studied traits
Leaf
Chlorophyll
Rate
Leaf Stomatal
Conductance
Relative
Water
Content
Water
Loss from
Separated Leaf
Biologic
Yield
Harvest
Index
Grain
Yield
Rasad 22.49 c 154.47 ab 87.17 ab 57.35 ab 14.97 ab 11.11 b 2.32 ab
Pishtaz 28.70 bc 119.53 b 89.38 ab 42.63 c 16.39 a 19.34 ab 3.25 a
Kenya-2002 43.37 a 169.33 ab 75.09 b 49.42 abc 12.93 ab 16.22 ab 2.12 b
Soltan-95 32.43 abc 177.44 ab 86.91 ab 41.86 c 11.75 b 16.45 ab 1.64 b
Soissons 31.46 bc 127.25 bc 90.97 ab 44.47 bc 12.03 b 20.45 a 2.42 ab
Seri 82 36.04 ab 197.30 93.32 a 62.16 a 12.45 ab 19.71 ab 2.25 ab
not a signi cant difference between the studied cultivars
based on the trait of photochemical ef ciency of photo-
system II. Gale et al. (2002) also observed that there was
not any change in photochemical ef ciency of photo-
system II due to the drought stress application among
various wheat cultivars.
LEAF CHLOROPHYLL RATE
Data mean comparison indicated among the studied
wheat cultivars, the highest leaf chlorophyll rate with a
mean of 43.37 CCI was related to the cultivar of Kenya
-2002 and it was put in group A along with cultivars of
Soltan-95 and Seri 82, and they didn’t show any sig-
ni cant difference based on this trait. Also, the cultivar
of Rasad with a mean of 22.49 CCI had the lowest leaf
chlorophyll rate.(Table 2).
Gregersen and Holm (2007) expressed that the chloro-
phyll content decreases during water stress and cultivars
with higher chlorophyll content show a higher resist-
ance in this stress condition. Chlorophyll content not
being suitable for assessing resistant towards drought
was expressed by Zarei (2007).
LEAF STOMATAL CONDUCTANCE
Data mean comparison indicated among the studied
wheat cultivars, the highest leaf stomatal conductance
with a mean of 197.30 mm/cms was related to the culti-
var of Seri 82 and it was put in group A along with culti-
vars of Rasad, Kenya-2002 and Soltan-95, and they didn’t
show any signi cant difference based on this trait. Also,
the cultivar of Pishtaz with a mean of 119.53 mm/cms
had the lowest leaf stomatal conductance, and it was put
in group B along with the cultivar of Soissons (Table 2).
RELATIVE WATER CONTENT
The highest relative water content rate (93.32 percent)
was related to the cultivar of Seri 82 and it was put in
group A along with cultivars of Rasad, Pishtaz, Soltan
98, and Soissons. On the other hand, the lowest relative
water content was related to the cultivar of Kenya-2002
with a mean of 75.09 percent (Table 2).
According to the results of the research conducted by
‘Abdoli et al. (2013), it was determined that leaf relative
water content rate decreased by 8.3 percent in drought
stress. Also, they reported that there was a signi cant
difference observed between studied cultivars based on
leaf relative water content.
WATER LOSS FROM SEPARATED LEAF
The cultivar of Seri 82 had the highest water loss from
separated leaf (with a mean of 62.16 oercent) and it
was in the best group along with the cultivars of Rasad
and Kenya-2002. On the other hand, the lowest water
loss from separated leaf with means of 41.86 and 42.63
percent was related to the cultivars of Soltan-95 and
Pishtaz (Table 2).
BIOLOGIC YIELD
Data mean comparison showed that the cultivar of
Pishtaz with a mean of 16.39 tons per hectare had the
highest biologic yield and it was put in the best group
along with the cultivars of Rasad, Kenya-2002 and Seri
82, and they did not show any signi cant difference in
this trait. On the other hand, the cultivars of Soltan-95
and Soissons were in the one statistical level and had the
lowest biologic yield (Table 2).
In drought stress, accelerated aging of photosynthetic
tissues and also decrease in current photosynthesis of
the plant lead to a decrease in biomass production.
Emam et al. (2007) and Pireivatlou et al. (2010) reported
results related to a decrease in biologic yield due to the
drought stress.
HARVEST INDEX
Mean comparison indicated that the highest harvest
index (20.45 percent) was related to the cultivar of
Anvari, Shahbazi and Imani
296 ASSESSING THE YIELD AND ITS RELATIONSHIP WITH SOME OF THE PHYSIOLOGIC TRAITS BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS
Soissons and it did not show any signi cant difference
with the cultivars of Pishtaz, Kenya-2002, Soltan-95
and Seri 82 and they were put in one statistical level.
Also, the cultivar of Rasad with a mean of 11.11 had the
lowest harvest index (Table 2).
Decrease in harvest index in drought stress condition
after owering is attributed to the decrease in access
to the current processed materials during grain ll-
ing period. (Emam, 2011; Emam and Niknejhad, 2011)
Decrease in harvest index due to the terminal drought
stress has been reported by other researchers as well.
(Emam, 2011; Wang et al., 2001) In drought stress con-
dition, decrease in photosynthetic activities ultimately
leads to a decrease in the transfer of produced materials
to the seeds and this leads to a decrease in harvest index.
(Gooding et al., 2003).
GRAIN YIELD
Data mean comparison showed that the cultivar of Pishtaz
with a mean of 3.25 tons per hectare had the highest grain
yield and it was put in one group along with the culti-
vars of Rasad, Soissons and Seri 82, and they didn’t show
any signi cant difference based on this trait. On the other
hand, the lowest grain yield was from the cultivars of
Soltan-95 and Kenya-2002 which were in the same sta-
tistical level and in the last ranking (Table 2).
Abdoli and Saeidi (2012) showed that irrigation cut
after pollination decreases the grain yield and thousand
kernel weight to 33.9% and 26.4% respectively in vari-
ous wheat cultivars.
Results from Ramezanpour and Dastfal (2004) showed
that 25 and 50 percent of decrease in the water lead to
21.8 and 40.7 percent decrease in grain yield, respec-
tively. Also, biologic yield index decreased by 16.4 and
32.2 percent, respectively.
CONCLUSION
Since modi cation of grain yield is usually dif cult due
to its low heritability, suitable physiologic properties
should be searched for in order to maximize the relation-
ship with formation of grain yield in various environ-
mental conditions. It seems that by studying phonologic
traits, such as relative water content, chlorophyll con-
tent, photochemical ef ciency of photosystem II, sto-
matal conductance and water loss from separated leaf,
cultivars resistive to drought stress could be easily iden-
ti ed. Based on retrieved results, the cultivar of Pishtaz
is the most yielding cultivar in water drought condi-
tion and planting it by the farmers in Ardabil Region,
in addition to leading a higher yield comparing to the
other studied cultivars, could entail a lower risk in drop
in production in case of drought stress emergence dur-
ing grain lling stage. Accordingly, cultivars of Rasad,
Soissons ans Seri 82 are in the next ranks.
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