responses of wheat genotypes to terminal drought

Int. J. Agricult. Stat. Sci., Vol. 8, No. 1, pp. 185-191, 2012
ISSN : 0973-1903
RESPONSES OF WHEAT GENOTYPES TO TERMINAL
DROUGHT STRESS BY USING STRESS TOLERANCE
INDICES
Farzad Aslani* and Mohammad Reza Mehrvar1
Department of agronomy, Science and Research Branch, Islamic Azad University, Tehran, Iran.
1
Physiology - Agronomy Unit of Department of Cereals Research,
Seed and Plant Improvement Institute, P.O. Box 31585-4119, Karaj, Iran.
E-mail: [email protected]
Abstract
One of the important abiotic stress factors limiting wheat production in Mediterranean basin is
drought. Eight wheat genotypes were evaluated under both drought conditions in post anthesis
stage (E1) and non-stress (E2) field environments using a randomized complete block for each
environment in 2007/08 and 2008/09 growing seasons. Five drought tolerance indices including
stress susceptibility index (SSI), stress tolerance index (STI), Stress Tolerance Index (TOL), mean
productivity (MP) and geometric mean productivity (GMP) were used. According to grain yield
under normal and terminal drought stress conditions the indices were adjusted. Greater values of
GMP, STI and MP indices were associated with higher yielding genotypes under both growing
conditions. Inversion of genotypes ranking was obtained for SSI and TOL. Higher TOL and SSI
values were associated with significant grain yield reduction in stressed environment suggesting
higher stress responses of genotypes. Higher grain yield was recorded in DN-11 during both
normal and terminal drought stress conditions whereas Bahar had considerably lower yield than
other genotypes. The results of our research were that MP, GMP and STI values were appropriate
parameters for selecting high yielding wheat genotypes in both normal and terminal drought
stress conditions.
Key words : Drought tolerance indices, Terminal drought stress, Wheat.
1. Introduction
Dryness is the most important factor limiting under production of crops in the world and
Iran. This Topic is more important in dry and semi-arid regions of the world [Kirigwi et al.
(2004)]. Drought stress at the grain filling period dramatically reduces grain yield [Ehdaie
and Shakiba (1996)]. Since dry matter production after heading is the main source of grain
yield in wheat [Saidi et al. (2008)], this stage of plant growth has a critical importance in
terms of drought. Thus, considering these generative stages for determining wheat tolerance
is one of the most plausible strategies for better crop improvement under water limited
*Corresponding author.
Received Oct. 23, 2011
Revised March 01, 2012
Accepted April 04, 2012
conditions especially in Mediterranean region. Some drought stress indices or selection criteria
have been suggested by different researches [Talebi et al. (2009) and Pireivatlou et al.
(2010)].
Different indices for evaluating the responses of genotypes in different environmental
conditions and their sensitivity and resistance are presented by Rosielle and Hambline (1981)
in the forms of tolerance index (TOL) and the average productivity index (MP). A high
TOL score indicated high relative response of the genotype to stress symptoms. The stress
susceptibility index (SSI) was introduced by Fischer and Maurer (1978). A low SSI score
shows low yield changes of genotypes in both stress and desirable conditions, an indication
of a good level of tolerance. A further stress tolerance index (STI) was introduced by
Fernandez (1992) on the basis that stable genotypes had higher STI scores and were therefore
more favorable. The GMP index also by Fernandez (1992) identified the geometric mean
yield of a genotype under both stress and normal conditions. A high correlation between STI
and GMP index was identified [Fernandez (1992)]. Moghaddam and Hadizadeh (2002)
found Stress Tolerant Index (STI) was more useful in order to select favorable corn cultivars
under stressful and stress-free conditions. Habibi et al. (2006) in their investigation on bean,
Ahmadi et al. (2000) on maize hybrids, Mohamadi et al. (2005) on wheat, introduced two
GMP and STI indices as the best indices separating genotypes with proper yield in both
stress and non stress conditions than other genotypes. Fernandez (1992) in study the yield of
genotypes in two environments and without drought stress than plants in two environments
appears to be divided into four groups: The genotypes that have high yield in stress and non
stress environments (group A). The genotypes that have high yield only in non stress
environments (group B). The genotypes that have high yield in stress environments (group
C). The genotypes that have weak yield in stress and non stress environments (group D).
Yield stability (a comparison of crop performance under normal and stress induced conditions)
has been accepted as the appropriate index to study the stress responses of genotypes to
humidity stress [Simane et al. (1993)].
Purpose of this study is to investigate different responses of eight wheat genotypes to
post-anthesis drought conditions based on some tolerance indices in two years field experiment.
2. Materials and Methods
The study was carried out at the Seed and Plant Improvement Institute, Karaj (Iran) in
2007/08 and 2008/09 growing seasons. In order to study seed yield and seed yield components
in wheat under terminal drought stress condition and assessment drought tolerance of eight
genotypes (Table 1) of wheat were evaluated in two separate RCBD design with 3 replications
under normal and terminal drought stress conditions. According to temperature and region
conditions, irrigation to the controlled units was applied at time intervals of 8 to 10 days. Plots
under drought stress at the post-anthesis stage and irrigation at the post-anthesis stage were
in accordance with normal routines however, irrigation was cut at the start of post-anthesis.
Each experimental unit consisted of three rows with distances of 20 cm and lengths of 6
meters.
Table 1 : G e n o t y p e s Table 2 : Drought tolerance indices.
studied.
Index
Formula
Reference
No.
Genotype
Stress Tolerance Index
STI=((GYi)×(GYp)/( GYi )2) (Fernandez,
1992)
1
DM-81-6
2
DM-82-1
3
Bahar
4
DN-11
5
DN-7
6
Pishtaz
7
WS-82-9
8
C-85-6
Mean Productivity
MP=(GYi+GYp)/2
(Rosielle and
Hamblin, 1981)
Geometric Mean Productivity
GMP=[(GYi)×(GYp)]0.5
(Fernandez,
1992)
Stress Tolerance
TOL=(GYi-GYp)
(Rosielle and
Hamblin, 1981)
Stress Susceptibility Index
SSI=[1-(GYp)/(GYi)]/SI
(Fischer and
Maurer, 1978)
(Stress Intensity)
SI = [1 - ( GYp ) / ( GYi )]
Drought resistance indices were calculated using the following relationships:
Where, GYp is the yield of cultivar under stress, GYi is the yield of cultivar under
irrigated condition, GYp and GYi are the mean yields of all cultivars under stress and nonstress conditions, respectively (Table 2).
Data were analyzed using SPSS17 for analysis of variance. Correlation between stress
indices and GYi and GYp was estimated by CORR proc. of SAS [SAS Institute (2001)].
Cluster analysis was established between these parameters by Cluster proc. of SAS.
3. Results
Drought is one of the major constraints to cereal production in Mediterranean areas
[Araus et al. (2003)]. Wheat is mostly grown under rainfed conditions in these areas and
frequently affected by post-anthesis drought because of the limited rainfall in spring.
The results of analysis of variance for grain yield and other related traits in both irrigated
and post anthesis drought conditions are given in Table 3. All characters were significant,
except biological yield in normal conditions and harvest index in post anthesis drought condition
that was non-significant. Which represents genotypes is genetic richness. These identified
traits can be used as selection criteria for resistance to drought stress. Fernandez (1992)
showed the most suitable selection criterion in the stress conditions must be able to separate
the genotypes with desired and similar display in both conditions. Considering that the best
indices are those with high correlation with the yield in both stress and non-stress conditions,
to be able to distinguish the genotypes with desired and similar display in both conditions
from other genotypes, the correlation between the yield and different indices was calculated
(Table 4).
From the correlation matrix, it is observed that the STI, GMP and MP indices have this
characteristic. Because these indices have a positive very significant correlation with the
genotypes yield in both normal and terminal drought stress conditions, thus the genotypes
with high amount of these induces may be identified as the most resistant genotypes.
4
7
7
Replication (Year)
Genotypes
Genotypes* Year
4
7
7
Replication (Year)
Genotypes
Genotypes* Year
19.8
0.96
4.7*
1.35
1.35
16
0.6
3.1**
4.1
10.7
Yield
16.8
36.1
63.1*
126.4
0.7
15.6
25.7
9.8**
121.2
167.2
Biomass
22.8
13.5
11
ns
366.3
55.6
18.2
8.4
33.2*
53.3
5
Harvest
Index
15.5
41.7
136**
163
10.2
15.1
41.7
136**
163
10.2
1000 Kernel
weight
Mean of Square
*, ** and , significant at 1% and 5% and non significant, respectively.
ns
CV
1
Year
Irrigation En
CV
1
Year
Stressed En
DF
Table 3 : Result of Analysis of variance for studied traits.
16.5
38369.6
131284.9**
198079.7
7668.3
17
56299.2
117995.8**
142672.8
82837.5
Number of spike
per square meter
22.9
32905362.5
93378723*
138344639.5
197261068.2
26.5
61815511.7
82291361.4*
73616183.8
4755.1
Number of kernel
Per square meter
28.1
145.8
242.4*
2279.3
25618.8*
10.8
67.2
127.8*
14.6
5.6
Relative water
content
The yield (GYi) under irrigated conditions has a very weak association with stress
conditions (GYp) depicting that high yield potential under best possible conditions does not
anticipate superior yield under stress conditions. Thus, indirect selection for a drought-prone
environment based on the results of optimum conditions will not be efficient. These results
are in agreement with those of Sio-Se Mardeh et al. (2006) and Gholipouri et al. (2009). In
stress condition, grain yield showed negative association with TOL and SSI [Gholipouri et
al. (2009)]. Therefore, TOL and SSI indices are suitable factors to identify wheat genotypes
with low yield and tolerant to drought because under stress, yield decreased with increasing
SSI. These findings are in consistence with the findings of Fernandez (1992) in mung bean,
Golabadi et al. (2006) in spring wheat and Farshadfar and Sutka (2003) in maize. Golabadi
et al. (2006) reported that selection for TOL will be worthwhile only when the target
environment is no-drought stressed.
The results of studying the level of genotypes resistance to the drought stress are provided
in Table 5. In this table, for eight genotypes of the Wheat, the values of GYp, GYi, STI, GMP,
MP, TOL and SSI and also the results of genotypes ranking based on this index are available.
According to the Table 5, the genotypes selected by GMP, STI and MP include the genotypes
with desired yield in both conditions. Totally, the genotypes selection was performed based
on high values of GMP, STI and MP. To assure the stability of the yield in the stress conditions,
the genotypes, from the selected genotypes, with the highest values of GYp were selected.
According to this, the cultivars DN-11, DN-7 and WS-82-9 were selected as the resistant
genotypes. This study showed that, the indices GMP, STI and MP are suitable indices in the
wheat that can be applied for yield stability and reaching the cultivars with high yield in both
conditions. These findings are in consistence with the findings of Fernandez (1992).
Based upon the results MP, STI and GMP indices have a similar ability to tolerant
genotypes separate drought sensitive and tolerant genotypes. Therefore, they can be used to
detect the studied genotypes which have low water requirements and/or suffer less yield
reduction by water shortage during their growth period, to be advised to cultivate in regions
with limited water resources in order to enhance cultivated area and production efficiency.
In order to determine the variation among different genotypes and determination of the
genotypes far or nearness, the Cluster Analysis was applied to place the similar cultivars in
one group. As it is appear in Fig. 1, with linear slicing from equality point of 0.60, the hybrids
are classified to three groups with high intra-group and low extragroup similarities. The
purpose is to specify the samples with the most distance from each other to be used in
hybridization programs and provide required variation for breeding programs. Also, by grouping
the individuals in similar groups, the amount of breeding works and the costs of researches
will reduce. In the Cluster Analysis, the lines were divided based on the yield, under irrigation
and terminal drought stress conditions into 3 groups (Fig. 1). The genotypes DN-11, was
placed in the first group. DN-11 had the highest STI, MP and GMP among other hybrids
(Table 4), and this average seed yield is higher than other groups (Figure 1), locating in group
A of Fernandez’s classification as tolerant hybrid. The genotypes Pishtaz, DM-82-1, WS82-9 and DN-7 were placed in the second group. These genotypes had an intermediate rank
Table 4 : Correlation coefficients between GYi, GYp and drought tolerance indices.
GYp
GYi
GYp
0.04
ns
STI
GMP
MP
TOL
SSI
0.75**
0.67**
0.78*
0.67**
0.83**
0.58**
0.82**
-0.53**
0.78**
-0.46**
0.99**
0.98**
0.99**
0.25*
0.30**
0.28**
0.34**
0.37**
0.38**
0.92**
STI
GMP
MP
TOL
*,** and, significant at 1% and 5%, respectively.
Table 5 : Resistance indices of 8 wheat genotypes under stress and non-stress environment.
Cultivars Rank GYi Rank GYp Rank STI Rank GMP Rank MP Rank TOL Rank SSI
DM-81-6
DM-82-1
7
5
6.37
6.91
7
5
4.59
5.22
7
5
0.61
0.75
7
5
5.40
6.01
7
5
5.48
6.07
4
6
1.78
1.69
3
5
1.12
0.98
Bahar
DN-11
8
1
6.29
7.67
8
1
4.42
5.85
8
1
0.58
0.93
8
1
5.27
6.70
8
1
5.35
6.76
2
3
1.87
1.82
1
6
1.19
0.95
DN-7
Pishtaz
2
4
7.27
7.10
3
4
5.56
5.32
2
4
0.84
0.79
2
4
6.36
6.14
2
4
6.41
6.21
5
4
1.71
1.78
7
4
0.94
1.00
WS-82-9
C-85-6
3
6
7.17
6.69
2
6
5.57
4.80
3
6
0.83
0.67
3
6
6.32
5.66
3
6
6.37
5.74
7
1
1.59
1.89
8
2
0.89
1.13
Fig. 1 : Dendogram of cluster analysis of the wheat genotype based on STI, GMP, MP, TOL, SSI and grain yield
(under both conditions).
and the genotypes Bahar, C-85-6 and DM-81-6 in the third group were placed. In the third
group, the genotypes were placed which had low yield in both conditions. These are located
in group D (low GYp and GYi) and in the most cases, have higher TOL and SSI values
among all hybrids (Table 2).
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