Water Deficit Stress Tolerance in Some of Barley Genotypes and Landraces under Field Conditions

In order to investigate the effects of water deficit stress on some agro-morphological and physiological traits of seven genotypes and five landraces of barley, a split plot experiment was conducted a completely randomized block design with four replications in 2011-2012 cropping season at experimental field of College of Agriculture, Payame Noor University of Center, West Azerbaijan, Iran. Analysis of variance revealed significant differences among genotypes and landraces for all of the studied traits, and showed highly significant effects of water deficit stress on all the studied traits. Based on correlation analysis, all the characters included in the study except leaf temperature and number of grain per spike showed significant positive correlation with grain yield under both conditions. In terms of physiological characters high significant correlation coefficient was found between relative water content and grain yield under stress condition; however, high significant correlation coefficient observed between fluorescence chlorophyll and grain yield under non-stress condition. 1000-grain weight had negative correlation with all characters except leaf temperature under non-stress condition. However, this character had significant and positive correlation with fluorescence chlorophyll, relative water content, SPAD value, spike length, number of spike per plant under stress condition. Considering the grain yield potential ‘Naghadeh’, ‘Piranshahr’ and ‘Mahabad’ landraces together with ‘CW3117-77’ genotype were ranked as the superior group of drought tolerant barley. On the other hand, ‘Naghadeh’ landrace was identified as a barley landrace that could be grown under both normal and water deficit stress conditions with high grain yield.


Introduction
Barley (Hordeum vulgar L.) is a major crop ranked fourth in the world-wide production of cereals.It is considered a primary staple food or feed crop in the semi-arid tropics of Asia, Africa, and South America.The grain is normally used as food and animal fodder, but recently it has been used as raw material for the production of beer.Barley is typically cultivated in the arid and semi-arid regions of Iran generally in areas with low precipitation that are not suitable for wheat (Baik and Ullrich, 2008).Drought is a significant limiting factor for agricultural productivity and generally inhibits plant growth through reduced water absorption and nutrient uptake.For improving the drought tolerance of crop varieties by plant breeding, it is necessary to identify genotypes with tolerance to drought stress during all growth stages.Landraces are still cultivated in traditional crop-growing areas.There is renewed interest in landraces and primitive cultivars as important sources of genetic variation (Brush, 1995) mainly because of the trend toward greater uniformity that has narrowed the genetic base of modern cultivars, thus increasing their vulnerability to biotic and abiotic stress (Moghaddam et al., 1997).
Decreased water availability generally results in reduced growth and final yield in crop plants.Plant drought tolerance is a highly complex trait that involves multiple genetic, physiological and biochemical mechanisms (Baik and Ullrich, 2008;Erdei et al., 2002).Drought affects morphological, physiological, biochemical and molecular processes in plants resulting in growth inhibition.The extent of these changes is dependent on the time, stage and severity of environmental stress (Cao et al., 2011).Measurements of different physiological processes of plants responses to drought are important information on the various strategies of the plant intended to remove or to reduce the harmful effects of water deficit in soil or plant tissues.Water deficit conditions cause water losses within the plant and result in relative water content (RWC) reduction.Therefore, RWC is widely used as one of the most reliable indicators for defining both the sensitivity and the tolerance of plants to water deficit (Rampino et al., 2006;Sanchez-Rodriguez et al., 2010).Rong-Hua et al. (2006) concluded that chlorophyll content could be considered as a reliable indicator in screening barley genotypes for drought tolerance.Experiments with a host of plants and different photosynthetic metabolism processes, which can be induced by varieties of plants and many biotic and abi-indices, i.e. leaf RWC, RCC, chlorophyll fluorescence and agro-morphological characteristics related to grain yield, under water deficit stress conditions.Experiment was conducted in split plot within a randomized complete block design with four replications.The experimental treatments consisted of irrigation levels as the main plot at second levels: irrigation after 70 mm evaporation from class A pan (without stress), irrigation after 150 mm evaporation from class A pan (water deficit stress) and twelve genotypes and landraces of barley as the sub plot were considered.Each plot contained 4 rows with 25 cm apart and 1m in length.All plots were irrigated after sowing and subsequent irrigations in beginning in tillering.Weeds were controlled by hand during crop growth and development.

Crop sampling and calculation
Agronomic characteristics and physiological criteria including: spike length (cm), number of spike per plant, number of grain per spike, 1000-grains weight (gr), grain yield (gr per plant), leaf temperature, fluorescence chlorophyll, relative chlorophyll content (SPAD value) and relative water content (RWC) were measured after of physiology maturity by selected 10 plants of each experimental plot randomly.For measuring physiological criteria was used the flag leaf.The chlorophyll content in the flag leaf was determined using a chlorophyll meter (SPAD-502, Japan).Five flag leaves of each cultivar grown in stress and non-stress conditions were measured after tillering stage.Three measurements in the middle of the flag leaf were otic factors, can directly or indirectly produce modification to fluorescence induction kinetics (Crudace, 2000;Percival and Baker, 1991).In addition, Slapakauskas and Ruzgas (2005) reported that measuring of chlorophyll provides information on quantitative and quantitative changes in photosynthesis.
The search for traits related to drought tolerance is an important step in cereals breeding and production.Field experiments investigating the yields of different cultivars under water deficit conditions are the most reliable way to assess their drought tolerance.Dencic et al. (2000) reported that many morphological and physiological characteristics were affected by drought stress.Also, they reported agronomic traits such as grain yield and its components are the major selection criteria for evaluating drought tolerance under field condition.Gupta et al. (2001) studied physiological and yield attributes of two wheat genotypes with stress at boot and anthesis.They indicated that number of grains, grain yield, biological yield, and harvest index decreased to a greater extent when water stress was imposed at anthesis stage.Therefore, physiological, agromorphological and biochemical approaches have a great importance in order to understand the complex responses of plants to water deficiency and develop rapidly new varieties.A physiological approach would be the most attractive way to develop new varieties (Araus et al., 2008) but breeding for specific, sub-optimal environments involves a deeper understanding of yield-determining process.
In the present study, five landraces together seven genotypes of barley were used to assess drought tolerance.The drought tolerance has been evaluated by physiological made randomly for each plant, and the average sample was used for analysis.Relative water content was determined according to Turner (1986), where fresh leaves were taken from each cultivar and each replication after tillering stage and weighed immediately to record fresh weight (FW).Then they were placed in distilled water for 4 h and weighed again to record turgid weight (TW).After that subjected to oven drying at 70°C for 24h to record dry weight (DW).The RWC was calculated using the following equation: RWC = ((FW -DW) / (TW -DW)) × 100 The chlorophyll fluorescence was measured by a chlorophyll fluorometer (Opti Science, OS-30MSA).Also, leaf temperature measurement were made using the infrared thermometer.

Statistical analysis
Simple analysis variance was performed for data using SPSS software.Mean comparisons were conducted using Duncan's multiple rang test.Percentage of reduction in characteristics due to drought stress was calculated as following: Where X̅ ns the mean of characteristic in given genotype/landrace under non-stress condition and X̅ ds is the mean of characteristic in given genotype/landrace under water deficit stress condition.Analysis of correlation coefficient between grain yield and other characteristics was used to determine the principle components influencing final grain yield (Fayaz and Arzani, 2011).
Stress susceptibility index (SSI) was calculated for each cultivar following Fischer and Maurer (1978): SSI = (1-Yds/Yns)/(1-(Ȳns/Ȳns)) Where Yds and Yns are the grain yield under stress and non-stress conditions, Ȳns and Ȳns are the average grain yield of all genotype/landrace under stress and non-stress conditions.

Results and discussion
Analysis of variance revealed significant (p≤0.01)differences among genotypes and landraces for all of the studied traits except of 1000-grains weight, and showed highly significant effects of water deficit stress on all the studied traits (Tab.2).Water deficit stress × genotypes interactions effect was also highly significant (p≤0.01) for all traits, suggesting different response of genotypes/landraces to each conditions.The maximum and minimum value of coefficient of variation belonged to number of spike per plant and plant height, respectively.
Means of agro-morphological and physiological characteristics under stress and non-stress conditions as well as reduction percent of reduction in the concerned characteristics due to water deficit stress are shown in Tab. 3. Leaf temperature ranged from 22.70 for 'Atlas46/Kavir' genotype and 'Sahand' landrace to 25.62 for 'CB' genotype under non stress condition; however, leaf temperature were highest under stress condition and ranged from 27.50 for 'Naghadeh' to 30.50 for 'Rihane-05' .Fluorescence chlorophyll ranged from 0.74 for 'CB' genotype to 0.80 for 'At-las46/Kavir' genotype and 'Sahand' landrace under stress conditions, however, this characteristics were lowest under stress condition and ranged from 0.69 for 'Rihane-05' to 0.74 for Naghadeh landrace.Also, SPAD value ranged from 39.95 to 43.07 for as46/Kavir under non-stress condition and ranged from 33.150 for 'Rihane-05' to 40.77 for 'Naghadeh' under stress condition.The highest reduction (21.90%) in SPAD value due to stress was observed in 'Rihane-05' genotype.Under non-stress condition RWC ranged from 73.32 for 'CB' genotype to 81.46 for 'Sahand'; however, under stress condition this characteristic ranged from 69.08 for 'Rihane-05' to 78.93 for 'Naghadeh' landrace.The decline in RWC in 'Rihane-05' and 'Atlas46/ Kavir' genotypes due to the stress was significantly less than all other genotypes and landraces.Decline of RWC reported in many researches (Farshadfar, 2012;Farshadfar et al., 2012).Ahmadi et al. (2012) showed that, RWC decline due to stress conditions.Plant height ranged from many researches (Gooding et al., 2003;Ozturk and Aydin, 2004;Shah and Paulsenl, 2003;Wardlaw, 2002).
Correlation studies are useful in measuring the strength and the direction of these relationships among the different characters and grain yield (Gashaw et al., 2007).So, to study the relationship, simple correlation between each pair of the characteristics for both conditions was calculated (Tab.4).Based on correlation analysis, all the characters included in the study except leaf temperature and number of grain per spike showed significant (p≤0.01)positive correlation with grain yield under both conditions.Garcia del Moral et al. (2003) reported that the number of spikes per squares meter in durum wheat was positively related to grain yield under rain fed conditions.In terms of physiological characters high significant (p≤0.01)correlation coefficient was found between relative water content and grain yield under stress condition; however, high significant (p≤0.01)correlation coefficient was found between fluorescence chlorophyll and grain yield under non-stress condition.Significant (p≤0.01) and negative correlation coefficient was found between grain tively.Riaz and Choudhy (2003) reported that genotypes with high 1000-grain weight under irrigated conditions may not be superior for this trait under moisture stress conditions.This is possible due to the limitation of moisture which forces plant to complete its grain filling in relatively shorter duration (Fayaz and Arzani, 2011).Number of grain per spike and 1000-grain weight decreased under water deficit stress condition.Probably water deficit caused male sterility which may in turn reflected in abortion of terminal and basal florets; hence, reduction in number of grain per spike and flowed by grain weight (Saini and Aspinall, 1981).In durum wheat Garcia del moral et al. (2005) observed 18.5% of reduction in number of grain per spike due to the negative effect of moisture stress.Also, 'Atlas46/ Kavir' 'Rihane-05' genotypes produced the highest and lowest grain yield than all genotypes and landraces under non-stress and stress, respectively.The highest reduction (85%) related to 'Rihane-05' genotype.Kirby and Jones (1997) and Giunta et al. (1993) also reported that mean decreased in grain yield under drought stress.In addition, decline of grain yield and components yield reported in Tab. 4. Correlation coefficient between physiological traits, grain yield and its components under normal (above diameter) and water deficit stress conditions (below diameter) yield per plant and number of grain per spike under stress condition.1000-grain weight also had negative correlation with all characters except leaf temperature under nonstress condition.However, this character had significant (p≤0.01) and positive correlation with fluorescence chlorophyll, relative water content, SPAD value, spike length, number of spike per plant under stress condition (Tab.4).These results are in agreement with the previous reported results on landraces of wheat under stress condition (Farshadfar et al., 2012).Moghaddam et al. (1997) reported negative correlation between number of grain per spike and 1000-grain weight.In the studies conducted by Sinha and Sharma (1979) and Belay et al. (1993), grain yield was positively correlated with each of the three primary grain yield components, with either positive or negative correlation between grain yield and plant height.Stress susceptibility index (SSI) was used as a selection criterion of drought tolerant in terms of minimization of yield reduction caused by drought stress as compared with non-stress conditions.Calculated SSI varied in from 0.62 to 1.30 for genotypes, and ranged from 0.53 to 1.15 for landraces (Tab.5).'Naghadeh' and 'Sahand' landraces that had the lowest and highest SSI values were found to be the most tolerant and the most susceptible landraces, respectively.Also, 'CB' and 'Rihane-05' genotypes that had the lowest and highest value were found to be the most tolerant and susceptible genotypes, respectively.This was in agreement with conclusions made based on agro-morphological and physiological characteristics.Fayaz and Arzani (2011) reported cultivars with low SSI values are moisture resistant because they have lesser reduction in grain yield under stress compared with non-stress condition.Nevertheless, this index per se appears to have serious limitations for the quantification of genotype reaction to moisture conditions, because it is based on minimizing yield reduction in stress compared with non-stress conditions.Therefore, selection for low SSI would tend to reduce yield in non-stress conditions (Dencic et al., 2000).However, barley genotypes and landraces identified as the stress tolerant by SSI may have tolerant mechanism, and can be used as sources of drought stress resistance in barley breeding programs for development of secondary germplasm with high grain yield potential.Considering the grain yield potential 'Naghadeh' , 'Mahabad' , 'Piranshahr' landraces and CW3117-77 genotypes were ranked as the superior group of drought tolerant barley.On the other hand, 'Naghadeh' landrace was identified as a barley landrace that could be grown under both normal and water deficit stress conditions with high grain yield.

Conclusions
This paper proposes a strategy to select the traits to be used in breeding programs.The result obtained from this study could be useful for barley breeders and seed producer in order to increase grain yield in water deficit con- To investigate the effects of water deficit stress, a research was carried out at experimental field of College of Agriculture, Payame Noor University of Mahabad Center, West Azerbaijan, Iran (latitude 36.46°N,longitude 45.43°E, Altitude 1385 m above sea level) during growing season of 2011-2012.The climate is characterized by mean annual precipitation of 330 mm, mean annual temperature of 12°C.Plant materials consisted of twelve genotypes and landraces of barley provided from Agricultural and Natural Resources Research Center of West Azerbaijan, Iran.The names of used in this investigation are shown in Tab. 1.
Tab. 2. Analysis of variance for agro-morphological traits in genotypes/landraces of barley grown under water deficit stress and normal conditions *and **: Significant at the 0.05 and 0.01 probability level, respectively; SL, NGS, NS, GW, Y and Ph indicate; spike length, number of grain per spike, 1000-grains weight, grain yield per plant and plant height, respectively †, † † and † † † indicate; 1.6E-4, 7.3E-5 and 1.05E-4; Tem, Flu, RCC and RWC indicate; leaf temperature, fluorescence chlorophyll, relative chlorophyll content and relative water content, respectively Different letter in each column indicate significant difference at p≤0.05.Tem, Flu, RCC, RWC, SL, NGS, NS, GW, Y and Ph indicate; leaf temperature, fluorescence chlorophyll, relative chlorophyll content (SPAD), relative water content, spike length, number of grain per spike, 1000-grains weight, grain yield per plant and plant height, respectively.
* and ns : Significant at the 0.01 probability level and Non-significant, respectively.Tem, Flu, RCC, RWC, SL, NGS, NS, GW, Y and Ph indicate; leaf temperature, fluorescence chlorophyll, relative chlorophyll content (SPAD), relative water content, spike length, number of grain per spike, 1000-grains weight, grain yield per plant and plant height, respectively. *