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Applied mathematics in Engineering, Management and Technology 2 (2) 2014:50-59
www.amiemt-journal.com
Bread wheat tolerance against drought at early growth stages and
grain filling period
Vahid Mollasadeghi1*,Taregh Ghanifathi2, Bahram Masoumzadeh3 and Ali Ahadi Aghahasanbeyglo3
1
Department of Agronomy and Plant Breeding, Ardabil branch, Islamic Azad University, Ardabil, Iran
2
Young Researchers Club, Tabriz Branch, Islamic Azad University, Tabriz, Iran
3
Department of Agriculture, Science and Research branch, Islamic Azad University, Ardabil, Iran.
*Corresponding author: Vahid Mollasadeghi ; E mail address: [email protected] Assistant Professor of
Abstract
Field and in vitro experiments were conducted on some bread wheat genotypes in
order to evaluate their tolerance against drought. During field experiment, 12 bread
wheat genotypes were evaluated based on randomized complete blocks design with
three replications under non-stressed and terminal humidity stress conditions. The
treatments used for in vitro evaluation included factorial combination of 12
genotypes being studied and two levels of drought stress (0 and -0.5 Mega Pascal)
based on complete randomized design with three replications. There was no
significant difference between genotypes being studied under non-stressed
condition, whereas the difference was significant under stressed conditions. Results
from analysis on correlation between drought tolerance and grain yield indices
indicated that STI, MP and GMP were useful for indentifying high yielding
genotypes under both drought-stressed and non-stressed conditions. In general, by
using drought tolerance indices based on grain yield we identified genotypes such
as Tous, 4057 and 4041 as tolerant against drought stress. During in vitro study,
increasing the level of drought stress led to decreased value of all the measured traits. Germination percentage was more
susceptible to drought than germination rate, whereas radicle length was more susceptible to drought than seedling length.
Germination vigor was identified as the most susceptible trait to drought among all the traits being studied. During in vitro
study, Gobustan exhibited the highest tolerance against drought in germination stage among all the genotypes being
studied. In this investigation, we did not observe any significant relation between traits measured in vitro and STI. Based
on the results, germination traits are not efficient direct criteria for selecting genotypes tolerant to drought in early growth
stages.
Keywords: bread wheat, drought tolerance, drought tolerance indices, Poly Ethylene Glycol, germination stress index
1.Introduction
In arid and semiarid regions, Diem wheat is exposed to drought stress during germination, greening and grain
filling stages. Consequently, it is critically important to select genotypes and introduce varieties to these regions
that could tolerate drought in abovementioned stages and produce high yield (Saeidi et al., 2007). A couple of
indices developed based on grain yield under drought stress and non-stressed conditions, have been proposed
for identifying genotypes tolerant to drought. An ideal selection index is one that distinguishes high yielding
genotypes from others under both stressed and non-stressed conditions (Fernandez, 1992). Rosielle and
Hamblin (1981) proposed Tolerance (TOL) and Mean Productivity (MP) indices. Higher values of TOL
represent the relative susceptibility of genotypes against stress, whereas MP index refers to the mean sum of the
yields of a given genotype under stressed and non-stressed conditions. In fact, TOL index is representing
difference resulted from the imposed stress. In other words, genotypes with lower TOL index produce lower
yield variation in stressed environment. Interestingly, its low value does not necessarily means that the
genotype has produced a high yield in non-stressed environment. Because, the yield of a cultivar may be low
under normal irrigation condition, while it suffer lower yield loss under drought stress and these lead to lower
TOL index and as a result erroneously it is designated as tolerant cultivar.
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Applied mathematics in Engineering, Management and Technology 2 (2) 2014
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Fernandez (1992) proposed STI (Stress Tolerance Index) as a criterion for selection of varieties tolerant to
drought stress. Higher values for this index represent high stress tolerating capability and high yielding
potentiality. According to some authors (Fernandez,1992; Khalilzade and Karbalai-Khiavi, 2002 and
Sadeghzade-Ahari, 2006) STI is the best index for the selection of genotypes. Because, it is capable of
distinguishing genotypes with high yield under both normal irrigation and drought stress conditions (group A)
from the two groups with genotypes that produce relatively high yield only either under normal irrigation
condition (group B) or under drought stress condition (group C). Another index proposed by Fernandez (1992)
was Geometric Mean Productivity (GMP). This index is more powerful than MP in distinguishing genotypes.
Another selection index is Stress Susceptibility Index (SSI) proposed by Fischer and Maurer (1978). These
authors found that genotypes with SSI lower than unit are more tolerant against drought. Thus, their yield loss
under drought condition is lower than mean yield loss of all other genotypes. Susceptible and tolerant genotypes
can be identified by using this index without taking into account their potential yield (Naderi et al., 2000). As
argued by Bouslama and Schapaugh (1984), Yield Stability Index (YSI) in evaluating the yield of a cultivar
under stressed condition relies on its yield under non-stressed condition and can be an ideal index for
identifying drought tolerant genotypes. Thus, cultivars with higher YSI values are expected to produce higher
yield under both conditions.
In the study conducted by Sio-Se Mardeh et al (2006) cultivars with higher YSI produced the lowest yield under
non-stressed and highest yield under stressed conditions. Yield Index (YI) classifies the cultivars only based on
the stress, whereas it does not distinguish high yielding genotypes under both stressed and non-stressed
conditions. They reported after evaluating 11 bread wheat genotypes that under mild stress conditions indices
such as STI, MP and GMP are useful for identifying high yielding genotypes for stressed and non-stressed
conditions.
Golabadi et al (2006) after evaluating 151 F3 and F4 families of Durum Wheat under both stressed condition
after flowering and without drought stress condition, reported that indices such as STI, MP and GMP had a
positively significant correlation with yield under stressed and non-stressed conditions. In contrast, indices such
as SSI and TOL had a negatively significant correlation with the yield under stressed conditions. Therefore,
drought tolerant genotypes can be selected based on either higher values of STI, Mp and GMP or lower values
of SSI and TOL.
Behmaram et al (2006) after evaluating drought tolerance of vernal colza cultivars reported that STI could
evaluate drought tolerance of the cultivars more effectively than do SSI and TOL. Khalilzadeh and Karbalaie
Khiavi (2002), Farshadfar et al (2001) and Choukan et al (2006) believe that the most efficient index for the
selection of stress tolerant cultivars is one that has a relatively high correlation with grain yield under both
stressed and non-stressed conditions. Therefore, understanding the correlation between stress tolerance indices
and grain yield in stressed and non-stressed environments, allow to identify the most efficient index.
Farshadfar et al (2001) after a study on pea reported the positively significant correlation of all the indices with
the yield under non-stressed condition, whereas they reported a negatively insignificant correlation between
TOL index and yield under stressed condition. Esmaeilzade Moghadam (2004) reported that MP, GMP and STI
were more efficient than SSI and TOL in identifying drought tolerant wheat genotypes and among the
mentioned indices STI was the most capable to distinguish the groups. Zarea-Fizabady and Ghodsi (2004)
reported that Stress Susceptibility Index (SSI) revealed a significant distinction between 20 wheat genotypes.
Fernandez (1992), Mozaffari (1995) and Koucheki et al (2005) also designated STI and GMP as the drought
tolerance indices. Fernandez (1992) in his 3-years-long study under normal and water limitation conditions
found that stress susceptibility indices had a significant correlation with grain yield. Nourmand Mo'eid et al
(2001) reported that correlation between indices such as GMP and STI and yield was positively significant.
Shafazadeh et al (2004) after studying wheat genotypes reported a very positively significant correlation
between the yield and indices such as MP, GMP and STI under stressed environment, whereas they reported a
positively significant correlation between the yield and all the drought stress and drought susceptibility indices
under non-stressed environment. They maintained that the positively significant correlation between the indices
and yield under both stressed and non-stressed conditions represents the efficiency of these indices to evaluate
how tolerant a given genotype is against drought.
Taghizadeh et al (2002) after evaluating drought tolerant sources for lentil genotypes in Ardabil Region found
that among the indices, MP, GMP and STI produced a positively significant correlation with yield in both
stressed and without stress environments.
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V. Mollasadeghi et al
Yield is influenced by three components namely yield potentiality, phonological consistency and drought
tolerance in drought environments. Relative contribution of drought tolerance to real yield may not be greater
than that of either high yield potential or optimum phonology. For instance, in a study conducted by Salim and
Saxana (quoted by Ouk et al., 2006) in 1993, for pea plant the relative contribution of the three components
ranged from 37 to 69% for avoiding drought (consistent phonology), 1 to 47% for yield potential and 4 to 17%
for drought tolerance in the space of three years.
Thus, genotypes selected from screening for drought tolerance based on grain yield, may either have a high
yield potential or have a consistent phonology, however lack any drought tolerance. Drought Response Index
(DRI) correct grain yield for variation in flowering date under drought stress condition and yield under nonstressed condition, ensuring drought tolerance of the selected genotypes (Ouk et al., 2006).
In drought climates with sporadic precipitation, developing desirable vegetation in early growth season is
considered one of the ideal features of the crops. In such regions the seedlings ability to emerge from lower
depths of the soil and their tolerance to drought in germination stage are the most important features associated
with the establishment of plantlet (Saeidi et al., 2006). Due to inconsistent soil setting and uncontrollability of
environmental factors, an in vitro experiment is especially important for evaluation of plant tolerance against
drought stress during germination stage (Mohammadi., 2000).
In order to evaluate drought tolerance under controlled environment and to develop water potential during
studies on germination, salts with high molecular mass such as poly ethylene glycol are often used to create an
osmotic solution simulating natural conditions (Jamshid-Moghaddam and Pourdad, 2006). Seeds sown in arid
and semiarid regions are characterized by high germination percentage, germination rate as well as germination
vigor (Saeidi et al., 2006).
In the study conducted by Saeidi et al., (2006) on two bread wheat genotypes, germination vigor decreased
more rapidly than germination percentage and rate as the stress levels increased (0, − 0.4, − 0.8, − 0.2 and −1.6
Mega Pascal). These authors maintained that seedling length is more susceptible to stress than radicle length.
Abdul-Baki and Anderson (1970) after studying barley stated that germination rate is more susceptible to water
stress than germination percentage and in higher osmotic potentials decrease with more stress intensity than
germination percentage. Dhanda et al (2004) after their study on wheat designated germination vigor as a more
drought susceptible trait compared with traits such as seedling length, germination percentage and radicle
length.
Zarei et al (2007) after conducting field and in vitro experiment on 20 bread wheat genotypes in order to study
their tolerance against drought reported that genotypes tolerant against drought on the field, also produced high
drought tolerance in vitro (germination stage). They found that STI had a positively significant correlation with
Germination Stress Index (GSI). These were consistent with results reported by Farshadfar et al (1992),
however Saeidi et al (2006) and Azizinia et al (2005) observed no consistency between drought tolerance in
field and that in vitro.
Based on forgoing comment, the aim of this investigation is to study drought tolerance of 12 bread wheat
genotypes in germination stage and terminal growth stages and to compare the results from screening of
genotypes for their drought tolerance in field and in vitro.
2.Materials and Methods
This study was conducted both on field and in vitro, at 2008-2009 cropping year. Genotypes being studied were
provided partly by Natural Resources and Agronomical Research Center of Ardabil Province and partly brought
from Azerbaijan. Field experiment was conducted as factorial based on randomized complete blocks design
with three replications and under two optimum irrigation and terminal drought stress conditions, at
experimental farm of Islamic Azad University, Ardabil Branch, based in Hasan Barough Village (5km west of
Ardabil). Each test plot included three 3-meters long rows recurring 20cm from each other. Each test plot
measured 7 × 3m, which 30cm from each ends of the plot were considered as margins. Seed usage amount was
450 seeds for unit area for each variety, which were sown on 11th of November. Irrigations were done in
traditional way, two of which were done in autumn and three as vernal. For drought stress treatments two times
of irrigation were not done after anthesis. No chemical or toxic fertilizers were used during the experiment and
weed control was done manually. In order to measure grain yield with more precision, the samples were taken
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V. Mollasadeghi et al
from competitive plants by deleting the margins. Indices for various drought tolerance were calculated using the
following equations:
During in vitro study, an experiment was conducted as factorial (first factor included 12 genotypes being
studied, whereas second factor included two drought stress levels) based on complete randomized design with
three replications. Amount of poly ethylene glycol 6000 required for creating osmotic potential of as much as –
0.5 Mega Pascal was calculated using Michel and Kaufman (1972) equations. Distilled water was used for
creating 0 mega Pascal osmotic potential (control). At first, wheat seeds were disinfected by 3% sodium
hypochlorite for 2 minutes. 50 seeds were cultured in every peteri dish. Germination test was run in the
Germinator with temperature of 25 ˚C, relative humidity of 70% and under 16 hours light and 8 hours dark
conditions. In order to measure germination indices the counting of germinated seeds was done daily, and at the
end of last day, the germination percentage test was calculated for each Peteri dish. Radicle length and seedling
length were measured based on mean length values of 30 plantlets. Equations proposed by Bouslama and
Schapaugh (1984) were used to calculate germination rate index (PI) and germination stress index (GSI) as
follow:
where, nd2, nd4, nd6, nd8 and nd10 are the number of germinated seeds in second, fourth, sixth, eighth and
tenth day, respectively.
Germination rate index was calculated by germinated seed percentage per day (G1: germination percentage at
first day and G2: germination percentage at second day and so forth) using following equation:
In addition, seed germination vigor was calculated using Abdul-Baki and Anderson (1970) equation as follow:
Where, VI is Seed Vigor Index; %Gr, germination percentage and MSH, sum of radicle length and seedling
length.
Statistic analyses were done using MSTAT-C, SPSS-16, Minitab-15 and Snagit-8 software. Mean comparisons
were conducted using Duncan’s multiple range test.
3.Results and discussion
Name of the genotypes and meteorological statistics of the study location have been listed in Table 1 and Table
2, respectively.
Table 1 – wheat genotypes used in this study
Number
Genotypes
Number
Genotypes
Number
Genotypes
1
2
3
4
Gascogne
Sabalan
4057
Ruzi-84
5
6
7
8
Gobustan
Saratovskaya-29
MV17/Zrn
Sardari
9
10
11
12
4061
4041
Sissons
Tous
Parameters
Table 2 – meteorological statistics of Ardabil in 2008-09 cropping year
2008
2009
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Applied mathematics in Engineering, Management and Technology 2 (2) 2014
V. Mollasadeghi et al
Aban Azar
Mean temperature
(˚C)
Precipitation (mm)
Dei
Bahman
Esfand Farvardin
Ordibehesht
Khordad
Tier
7.7
2.9
1.9
3.2
6.3
9.1
12.6
15.2
8.4
48.8
8.6
11.4
18.5
24.3
27
30
18.6
3.4
Based on the results from analysis of variance for grin yield, the genotypes being studied had not a significant
difference under non-stressed condition, whereas they produced significant difference under stressed condition,
at 1% probability level. Results from mean comparisons of grain yield (Table 3) showed that Tous genotype
(3.93 ton/ha) and Saratovskaya-29 (2.27 ton/ha) had the highest and lowest yields under stressed condition,
respectively, whereas under non-stressed condition, 4057 (4.38 ton/ha) and Saratovskaya-29 (3.09 ton/ha) had
the highest and lowest yields.
Results from analysis of correlation between drought tolerance indices and grain yield under both stressed and
non-stressed conditions (Table 4) showed that indices such as GMP, MP and STI had a positively significant
correlation with grain yield under stressed and non-stressed conditions, at 1% probability level. Thus,
abovementioned indices were the most efficient indices to identify the superior genotypes. The abovementioned
results are consistent with those reported by Sio-Se Mardeh (2006), Golabadi et al (2006) and Geravandi et al
(2010).
In the present study, YI had a positively significant correlation with the yield under stressed condition. This
index classified the genotypes only based on yield under stressed condition and could not identify high yielding
genotypes under both conditions. Furthermore, YSI had a positively significant correlation with yield under
stressed condition, whereas it had simply positive correlation with yield under non-stressed condition. Thus, it
selects high yielding genotypes under stressed condition, whereas they select low yielding ones under nonstressed condition. This index was not capable of identifying high yielding genotypes under both stressed and
non-stressed conditions. These were consistent with results reported by Sio-Se Mardeh et al. (2006) and
Geravandi et al (2010).
Based on numerical values of indices such as STI, MP and GMP (Table 3) and also the 3D diagram (Fig. 1)
drawn based on grain yield under both conditions and STI; genotypes such as Tous, 4057 and 4041 were
identified as high yielding under both stressed and non-stressed conditions and designated as drought tolerant
genotypes. These genotypes were more drought-tolerant both in early growth stages and in grain filling stage
than others.
Table 3 – indices of tolerance and susceptibility to drought and of grain yield under drought stress and nonstressed conditions
Ys
Yp
TOL
MP
GMP
Genotypes
SSI
STI
YI
YSI
Gascogne
Sabalan
4057
Ruzi-84
Gobustan
Saratovskaya-29
MV17/Zrn
Sardari
(Ton/ha)
(Ton/ha)
(Ton/ha)
(Ton/ha)
(Ton/ha)
2.47 cd
3.16 abc
3.39 ab
2.87 bcd
2.75 bcd
2.27 d
3.25 abc
3.09
abcd
3.16 abc
3.53 ab
2.73 abc
3.92 a
3.87 ab
3.80 ab
4.38 a
4.00 ab
3.73 ab
3.09 b
3.62 ab
1.41
0.64
0.98
1.13
0.97
0.82
0.37
3.17
3.48
3.88
3.44
3.24
2.68
3.44
3.09
3.46
3.85
3.38
3.20
2.64
3.43
1.86
0.86
1.15
1.45
1.34
1.36
0.52
0.67
0.84
1.03
0.8
0.71
0.49
0.82
0.81
1.04
1.11
0.94
0.9
0.74
1.07
0.64
0.83
0.78
0.72
0.74
0.73
0.9
3.92 ab
0.83
3.51
3.48
1.09
0.84
1.01
0.79
4061
3.67 ab
0.51
3.42
3.40
0.71
0.81
1.04
4041
3.88 ab
0.35
3.70
3.70
0.46
0.95
1.16
Sissons
3.64 ab
0.73
3.10
3.07
1.08
0.66
0.9
Toos
4.00 ab
0.08
3.96
3.96
0.1
1.09
1.29
Coefficient
variation
14.48
16.60
percentage
means values with common letters in each column have no significant difference based on Duncan Test, at 5%
probability level
54
0.86
0.91
0.79
0.98
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Applied mathematics in Engineering, Management and Technology 2 (2) 2014
V. Mollasadeghi et al
indices have been calculated based on means of data and have not been subject to analysis of variance
Table 4 – correlation coefficients of drought tolerance indices with grain yield under drought stress and
irrigation conditions
Ys (Ton/ha)
TOL
SSI
MP
GMP
STI
YI
YSI
Ys (Ton/ha)
1
-0.730**
-0.850**
0.932**
0.953**
0.953**
1.000**
0.850**
Yp (Ton/ha)
0.601*
0.108
-0.091
0.850**
0.808**
0.808**
0.601*
0.091
* and ** Significantly at p < 0.05 and < 0.01, respectively
Ys : Yield in stress condition
Yp : Yield in non- stress condition
TOl : Tolerance
MP : Mean productivity
GMP : Genomic Mean productivity
SSI : Stress susceptibility Index
STI : Stress Tolerance Index
YI : Yield Index
YSI : Yield Stability Index
groups
1
2
3
1.0
STI
0.8
4.0
0.6
3.5
0.4
3.0
3.0
3.5
Yp (ton/ha)
4.0
2.5
Ys (ton/ha)
Genotypes
4041
4057
4061
Gascogne
Gobustan
MV17/Zrn
Ruzi-84
Sabalan
Saratov sk aya-29
Sardari
Sissons
Toos
4.5
Fig 1. Selection of drought tolerant genotypes using Stress Tolerance Index (STI)
Analysis into main components was done for yield under stressed and non-stressed conditions and drought
tolerance indices and due to bulk of the value of variance accounted for by first two components (99.91% in
total), the Bi-plot (Fig. 2) was drawn based on these two components. First component with positively high
coefficients for STI, GMP, MP and yield under stressed and non-stressed conditions, was designated as the
component of yield stability and of tolerance to drought stress. This component accounted for 52.42% of data
variation. Second component, due to positively high coefficients of SSI, TOL and yield under non-stressed
condition, was designated as susceptible to drought stress and yield potential. This component accounted for
47.28% of data variation. Bi-plot diagram indicated that genotypes such as Tous, 4057 and 4041 located near to
vectors of important drought tolerance indices that are STI, MP and GMP. Genotype 4041 was more oriented
towards vector of grain yield under stressed condition, thus the mentioned genotype in addition to being
drought tolerant, also produced higher yield under stressed condition. Genotype 4057 was more oriented
towards vector of yield under non-stressed condition and this indicates that high values of drought tolerance
index in these genotypes have been mostly due to their high yield under non-stressed condition. Sardari and
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V. Mollasadeghi et al
Ruzi-84 genotypes were among the important drought stress tolerance and drought susceptibility indices. Thus,
these genotypes are considered as semi-susceptible to drought. Based on Bi-plot diagram, genotypes such as
Gascogene and Gobustan were designated as potentially high yielding and susceptible to drought. Genotypes
such as Sissons, 4061 and MV17/zm were designated as less susceptible to drought stress and potentially low
grain yielding. The acute angle between STI, MP and GMP indices represents a high correlation between these
indices. In addition, the high correlation between TOL and SSI indices is evident in Bi-plot diagram.
Fig. 2. Bi-plot for five drought resistance indices for 12 bread wheat genotypes based on first two components
Results from analysis of variance for measured traits obtained from in vitro study (Table 5) showed that
genotypes being studied were varying significantly in terms of all measured traits, at 1 and 5% probability
levels. In contrast, there is no significant difference between drought stress levels (0 and – 0.5 mega Pascal) in
terms of all the traits, at 1% probability level.
Sources of variation
Stress levels
Degree
of
freedom
1
Table 5- ANOVA for in vitro measured traits
Mean squares
germination germination seedling
radicle
percentage
rate
length
length
3244.7**
0.0007**
22.68** 527.854**
Genotypes
11
775.1**
0.00007**
Stress levels ×
11
73.224
0.000007
Genotypes
Error
48
51.85
0.000009
C.V (%)
8.14
2.11
and ** Significantly at p < 0.05 and < 0.01, respectively
germination
vigor
901.71**
germination
rate index
20882.9**
4.432**
8.739*
25.442**
2517.99**
0.88**
5.574
7.413*
93.8
0.23
10.75
3.52
30.47
4.17
23.44
168.04
11.96
Saeidi et al. (1) also observed a significant variation between radicle length and seedling length in various
drought stress levels (0 and – 0.5 mega Pascal).
The interaction of stress levels × genotypes for seedling length (Fig. 3) also revealed that genotypes such as
Gobustan and Sardari had the highest seedling length at non-stressed level. Stress at – 0.5 mega Pascal level led
to decreased seedling length for all the genotypes, apart from Sardari, which had a significant decrease. At zero
mega Pascal level, genotypes such as Gobustan, Sardari and Saratovskaya-29 had the longest seedlings,
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Applied mathematics in Engineering, Management and Technology 2 (2) 2014
V. Mollasadeghi et al
whereas Gascogene and Sissons had the shortest seedlings. At –0.5 mega Pascal level the highest seedling
length belonged to Sardari. These results are in line with those reported by Geravandi et al (2010).
Fig. 3, Mean comparison of interaction between stress levels and genotypes for seedling length
The interaction of stress levels × genotypes was significant for germination vigor. Based on Fig. 4 various
genotypes varied significantly under non-stressed condition (distilled water), for instance, Gobustan and Sardari
had the highest and Gascogene, Saratovskaya-29 and Sissons had the lowest germination vigor. As the osmotic
potential decreased, germination vigor, as opposed to traits such as germination rate and percentage, decreased
with comparatively higher rate and slope. Saeidi et al (2006) also reported similar results. Dhanda et al (2004)
introduced germination vigor most susceptible trait as compared with seedling length, germination percentage
and radicle length. At – 0.5 mega Pascal osmotic potential, Gobustan and Sissons had the highest and lowest
germination vigor, respectively. In general, results from mean comparisons revealed that genotypes being
studied varied significantly in terms of the measured traits. Gobustan was in better situation than other
genotypes in terms of most of the studied traits at various drought levels.
Fig. 4, Mean comparison of interaction between stress levels and genotypes for germination vigor
Results from analysis of correlation between studied traits obtained during in vitro study have been listed in
Table 6. Germination rate index had a positively significant correlation with germination percentage,
germination rate, and seedling length and germination vigor. Traits and indices measured in vitro had a positive
but insignificant correlation with STI and grain yield in this study. Thus, one can conclude that using poly
ethylene glycol in various concentrations and applying stress in vitro as well as studying germination traits
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V. Mollasadeghi et al
cannot give an understanding on susceptibility or tolerance of a given genotype in post-anthesis stage and this
method cannot be used as an indirect selection criterion to identify genotypes tolerant to drought after anthesis.
In the study conducted by Saeidi et al (2006) there was a positively significant correlation. Saeidi et al (2006)
also reported that the correlation between germination traits and drought tolerance indices based on grain yield
was not significant. Azizinia et al (2005) also reported similar results. Insignificant correlation between
germination traits and STI apparently accounts for other known and unknown factors involved in yield
production during post-germination stages. As a result, factors potentially effective on the plant during sensitive
yield development stages, particularly flowering stage, will maintain the highest significant correlation with the
yield.
Results from this study indicated that increased drought stress during germination sage resulted in decreased
values of traits being studied. Germination rate was more susceptible to drought stress. In this study, there was
no significant relation found between traits measured in vitro and drought tolerance of genotypes on the field.
Based on these results, germination traits were not efficient indirect criteria to select genotypes capable of
tolerating drought under field condition. Genotypes such as Tous, 4057 and 4041 on field and Gobustan in vitro
produced higher drought tolerance than others.
Table 6- Simple correlation coefficients between traits in vitro condition
germination germination seedling
percentage
rate
length
germination
1
percentage
germination rate
0.826**
seedling length
0.501
radicle length
0.333
germination vigor
0.759**
germination rate
0.960**
index
Yield in stress
0.385
condition
Tolerance index
0.467
and ** Significantly at p < 0.05 and
radicle
length
germination germination
vigor
rate index
Yield in
stress
condition
1
0.715**
0.472
0.871**
1
0.254
0.853**
1
0.639*
1
0.948**
0.636*
0.388
0.841**
1
0.563
0.286
-0.022
0.284
0.488
1
0.545
0.258
< 0.01, respectively
-0.021
0.299
0.527
0.953**
Tolerance
index
Reference
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