沙漠研究 24-1, 261-264 (2014)
Ἃ₍◊✲ 24-1, 261 - 264 (2014)
Journal of Arid Land Studies
Journal of Arid Land Studies－ DT11 Refereed Paper －㸫DT11 Refereed Paper㸫

Variation in Response to Salt Stress at Seedling and Maturity Stages
among Durum Wheat Varieties
Nejla TURKI1), Tariq SHEHZAD1), 2), Moncef HARRABI3), Moktar TARCHI3) and Kazutoshi OKUNO*1), 2)
Abstract: Salinity is a significant constraint for crop quality and production, affecting wheat growth, yield and quality in the major
wheat growing regions of the world. To counter this, it is necessary to develop tolerant varieties through selection and breedingtechniques. The objective of this study was to investigate variation in response to salt stress among 119 worldwide landraces andimproved varieties of durum wheat at seedling and maturity stages. The results showed that at seedling stage 100 mM NaCldecreased chlorophyll content, leaf length, number of tillers per plant, number of leaves per plant, shoot length and shoot fresh and dryweights, while at maturity stage plant height, the number of fertile spikes per plant and the number of seeds per spike were affected by
100 mM NaCl. The shoot fresh and dry weights were the most affected traits at seedling stage; however the number of fertile spikes
and the number of seeds per spike were the most affected traits at maturity stage. These results reflected the importance of these traits
for the assessment of salt tolerance in durum wheat varieties. On the basis of salt tolerance/susceptibility scale, most of tolerantvarieties were originated from North African countries such as: Morocco, Egypt, Algeria and Tunisia and East African countries suchas Ethiopia and Eritrea. Thirty-six highly tolerant and 16 highly susceptible varieties were evaluated in the saline area in the field.
Results showed that tolerant varieties could grow and develop biomass under saline conditions. In contrast, susceptible varieties
could not even emerge in the stressed condition.
Key Words: Durum wheat, Maturity stage, Salt stress, Seedling stage

1. Introduction
Wheat is the most widely growing cereal crop andoccupies 17% of the total cultivated land in the world. It is
the staple food for 35 percent of the world’s population, andprovides more calories and protein in the world’s diet than any
other crop. Salt stress appears to be one of the constraints forwheat production: more than 800 million hectares of land
worldwide, or more than 6% of the world’s total land area
(FAO, 2008), are salt affected, severely impairing theagricultural production in many countries. Durum wheat ismore sensitive to salt stress than bread wheat. Screening
wheat for salt tolerance at the seedling and maturity stages has
been performed by a number of different researchers (Akramet al., 2002; Khayatnezhad and Gholamine, 2011); however,achieving genetic increases in yield under salt stress has
consistently proven a difficult challenge for plant breeders(Khayatnezhad et al., 2010). Further screening for salt
tolerance and its validation in salt affected fields are stillneeded to better understand the mechanism of tolerance and toimprove salt tolerance in wheat. The present study was* Corresponding Author: okuno.kazutoshi.fu@u.tsukuba.ac.jp

conducted to identify some promising parental lines andmorphological parameters, and to select tolerant andsusceptible varieties at the seedling and maturity stages, withparticular focus on their use for future breeding programs indurum wheat.

2. Materials and Methods
2.1. Plant materials
In order to study the effects of salinity stress at the seedlingand maturity stages in durum wheat, two types of experiments
were conducted using a completely randomized complete
block design with two replications. In these experiments, 119
worldwide landraces and improved varieties of durum wheat
were evaluated at two levels of salinity (0 and 100 mM NaCl).
The third experiment was conducted in the field using 52
varieties of durum wheat selected based on their highperformance in tolerance/susceptibility to salt stress (36 werehighly tolerant and 16 highly susceptible). In this experiment,
we used a completely randomized design with threereplications.

㸦Received, September 14th, 2013; Accepted, January 3rd, 2014㸧

Tennodai 1-1-1, Tsukuba, Japan
1) Laboratory of Plant Genetics and Breeding Science, Graduate School of Life and Environmental Sciences, University of Tsukuba, Japan
2) Alliance for Research on North Africa (ARENA), University of Tsukuba, Japan
3) Laboratory of Genetics and plant breeding, Department of Crop Sciences and Biotechnology, National Agronomic Institute of Tunisia (INAT), Tunisia

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2.2. Experiment at seedling stage
The seedling stage experiment was conducted in aglasshouse using perforated pots filled with soil. Salt wasapplied at the 3-leaf stage. Forty days later all plants wereharvested and fresh and dry weights of shoots after drying allplants in oven for 72 hours at 70°C were recorded. Before
harvesting, several traits were measured such as chlorophyll
content using SPAD meter, number of tillers, number of leaves
per tiller, shoot length and leaf length.

Fig. 1. Evaluation of chlorophyll content (CH) under salt stress.

2.3. Experiment at maturity stage
The experiment was also conducted using perforated pots
filled with soil. Salt was applied at booting stage and before
this stage all plants were irrigated with tap water. During thisexperiment, different traits were measured such as plant height,
the number of fertile spikes and the number of seeds per spike.
Fig. 2. Evaluation of shoot dry weight (SDW) under salt stress.

2.4. Field experiment
The experiments were carried out during the 2011-2012
growing season (1 year) in saline field of Seliana (region: Krib)in Tunisia (semi-arid). The surface layer (0-30 cm depth) of
the soil had a silty clay loam texture. The electricalconductivity (EC) of the soil was around 8 dS m-1. In thisregion, the mean of annual precipitation and temperature weregiven as 420 mm and 18°C, respectively.
Seeds of 52 varieties of durum wheat were sown in this soil
and the traits recorded are the number of tillers per plant,
number of leaves per plant, number of spikes per plant, numberof seeds per spike, days from planting to heading, days fromplanting to flowering, plant height and 1000 grain weight.
2.5. Statistical analysis
The data were analyzed separately using ANOVA provided
by JMP software, version 9 (SAS Institute Inc. 2010).
Correlation analyses were conducted using Pearson correlation
coefficient (r) to determine the relationship among all traits.

3. Results and Discussion
3.1. Salt effect on durum wheat at the seedling andmaturity stages (Glasshouse experiments)
Salt stress induced a significant variation in plant growthduring the experimental period. Under salt stress conditions,considerable reductions in various agronomic traits wereobserved in all varieties. At seedling stage, the chlorophyll
content varied from 10.75% to 33.25%, with an average of20% (Fig. 1). This trait was highly affected by salt stress with35% reduction as compared with the control. Highaccumulation of sodium in plant tissues has been reported as an
influential factor in the reduction of photosynthetic pigments

and the rate of photosynthesis (Sairam et al., 2002; Ashraf,2004). The oldest leaves showed chlorosis, and fell to theground, as a result of a prolonged period of salt stress(Hernandez et al., 1995; Gadallah, 1999; Agastian et al., 2000),
which affects the decrease of chlorophyll content in leaves.
Shoot fresh and dry weights were the most affected traits
with 48 and 42% reductions compared with the control
respectively (Fig. 2). The reduction of these traits waspreviously reported by Singh et al. (1994) who found that alt
stress reduces leaf area photosynthetic ability and dry matteraccumulation. The number of tillers ranged from 3 to 12 with
6 on average, while under control conditions the average was 8.
The reduction of the number of tillers in wheat under salt stresshave been previously reported by El-Hendawy (2005) andGoudarzi et al. (2008). The number of leaves and the leaf
length were less affected by salt stress with a reduction of 19
and 22%, respectively, as compared with the control.
The shoot fresh and dry weights were important for theassessment of salt tolerance in wheat because a positive
correlation existed between these traits and yield relatedparameters. However, further verification is still needed tocontrol the effect of salt stress at later stages.
The evaluation of final grain yield and of growthparameters determining grain yield is critical to breeding
programs. The final yield of wheat is determined by thenumber of spikes per plant and various yield components, suchas the fertile spikelet number, grain number, and grain weight.
For instance, in this study the number of fertile spikes, ranging
from 0 to 8, was highly affected by salt stress with 57%
reduction as compared with the control. The reduction of thistrait was reported by several studies such as Maas and Grieve(1990), Grieve et al. (1993) and Francois et al. (1994) who263

demonstrated that salt significantly reduced the number of
spikelet primordia on the main spike.
The plant height was significantly (p < 0.05) decreased bysalt stress. Under salt stress conditions, the mean values ofthis trait ranged from 43.5 to 103 cm with an average of 71cm.
The reduction of plant height under salt stress conditions wasalso reported by Khan et al. (2007). The number of seeds
was decreased to 56% as compared with the control.
According to Francois et al. (1994) a reduction in floret
viability seriously affected the total number of kernels per
spike and this effect was more pronounced in susceptible thanin tolerant varieties. The number of fertile spikes can beconsidered as one of the main traits to evaluate salt tolerance inwheat because only tolerant varieties could produce fertile
spikes, while the susceptible ones produced sterile spikes. On
the basis of tolerance/susceptibility scale, we designatedvarieties with a reduction of less than 25% in number of fertile
spikes as a highly tolerant variety. Most of the varieties
belonging to this group were originated from African counties
such as Ethiopia, Egypt, Algeria, Morocco and Tunisia.
However, further experiments in the field are required toconfirm the stability of these varieties under salt stressconditions. Therefore, 52 varieties were selected for this field
experiment based on the higher performance oftolerance/susceptibility to salt stress (36 selected as highly
tolerant to salt and 16 as highly susceptible).

Fig. 5. Evaluation of the number of seeds per spike under salt stress.

3.2. Field experiment
In the previous experiments we demonstrated theimportance of some traits such as shoot fresh and dry weights,
number of fertile spikes and the number of seeds per spike forthe evaluation of salt tolerance at seedling and maturity stages.
Here, we will focus mainly on traits at maturity stage to checkthe stability of yield parameters under salt conditions, since
improving the grain yield of wheat under salt stress is
consistently the main target in plant breeding.
In this experiment, highly susceptible varieties originatedmainly from Asian countries could not germinate. In contrast,
the tolerant ones could grow and reach final stage ofdevelopment.
The number of tillers ranged from 3 to 8 with 5 on theaverage and was highly associated with yield parameters.
The plant height showed a significant (p < 0.05) correlation
with yield components. Under salt stress conditions, this trait
ranged from 65 to 110 cm with an average of 84.
Days to heading and days to flowering were recorded inthis experiment in order to evaluate the effect of salt stress on
the days to maturity. Results showed that the number of days
to heading varied from 172 to 185 with an average of 179 days
(Fig. 3), while the days to flowering ranged from 176 to 189

days with an average of 184 days (Fig. 4). Some varietiessuch as Trigo (97) from Peru had the lowest number of days toheading and this could be considered as a mechanism fortolerance to stress where plants matured fast to complete theirlife cycle.
Under saline field conditions, the number of spikes withintolerant genotypes ranged from 3 to 8 with an average of
5.3.The varieties durum 36-6 from Ethiopia (80) and Herculesfrom Canada (6) had the highest number of spikes under salt
stress.
The number of seeds per spike ranged from 26 to 78 withan average of 39 (Fig. 5). The variety ELS 6404-126-3 (8)from Eritrea (East Africa) had the highest number of seeds per
spike under saline field conditions. This variety is a candidate
gene pool for improvement of salt tolerance in durum wheat.
Thousand kernel weight (TKW) was also recorded in thisstudy and the mean value of this trait ranged from 18 to 60
with an average of 34. The variety Malta 2 (58) from Malta
has the highest value of TKW under salt stress conditions
which reflects the importance of this variety for theimprovement of yield in durum wheat.
In this experiment, yield related traits such as the numberof spikes, the number of seeds per spike and TKW wereFig. 3. Evaluation of days to heading under salt stress.

Fig. 4. Evaluation of days to flowering under salt stress.

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correlated with each other and with various other traits. Dueto this correlation, these traits can be used as selection criteria
for the assessment of salinity tolerance in durum wheat
varieties under saline field conditions. Many scientists had
classified crop species on the basis of grain yield under stressconditions (Sadiq et al., 1994; Jafari-Shabestari et al., 1995;
Anderson et al., 1996). Ayers and Wescot (1976) reported
that wheat yield decreased by 50 percent at soil saturation
extracts of 13 dS/m. Durum wheat has a higher sensitivity tosalt than bread wheat. The threshold at which grain yield
starts to decrease with an increase in soil salt is 5.9 dS/m fordurum wheat and 8.6 dS/m for bread wheat. Furthermore, theyield in durum wheat was decreased at a higher rate withincrease in salt content in soil than bread wheat (Maas andGrieve, 1986; Acevedo et al., 2003).

4. Conclusion
The focus of this study was to select the varieties which
exhibit less reduction of yield components under salt stressconditions. All the 36 varieties selected from the previous
experiment in the glasshouse showed their ability to grown insaline field conditions and produce grain yield. However,some varieties which had the lowest reduction in several traits
under stress conditions can be used for the improvement of salt
tolerance in durum wheat. The variety Malta2 (58) from
Malta is one of the important varieties in salt tolerance to be
used in future breeding of durum wheat.

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