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Effects of Salinity and Drought Stress onGrain Quality of Durum WheatS. Houshmand a , A. Arzani b & S. A. M. Mirmohammadi-Maibody ba Department of Plant Breeding and Biotechnology , College ofAgriculture, Shahrekord University, Shahrekord , Iranb Department of Agronomy and Plant Breeding, College ofAgriculture , Isfahan University of Technology , Isfahan , IranAccepted author version posted online: 20 Nov 2013.Publishedonline: 30 Jan 2014.

To cite this article: S. Houshmand , A. Arzani & S. A. M. Mirmohammadi-Maibody (2014) Effects ofSalinity and Drought Stress on Grain Quality of Durum Wheat, Communications in Soil Science andPlant Analysis, 45:3, 297-308, DOI: 10.1080/00103624.2013.861911

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Communications in Soil Science and Plant Analysis, 45:297–308, 2014Copyright © Taylor & Francis Group, LLCISSN: 0010-3624 print / 1532-2416 onlineDOI: 10.1080/00103624.2013.861911

Effects of Salinity and Drought Stress on GrainQuality of Durum Wheat

S. HOUSHMAND,1 A. ARZANI,2

AND S. A. M. MIRMOHAMMADI-MAIBODY2

1Department of Plant Breeding and Biotechnology, College of Agriculture,Shahrekord University, Shahrekord, Iran2Department of Agronomy and Plant Breeding, College of Agriculture, IsfahanUniversity of Technology, Isfahan, Iran

This work aimed to assess the influences of soil salinity and drought stresses on grainquality characteristics of selected salt-tolerant genotypes differing in salinity tolerancein durum wheat. This study was conducted under control, drought, and saline fieldconditions in separate experiments during 2 years. A randomized complete block designwith three replications was used for each experiment. The results showed significanteffects of genotype and environmental conditions on all grain-quality related traits.Salt and drought stress caused the significant increment of grain protein content, wetand dry gluten contents, and sodium dodecyl sulfate (SDS) sedimentation volume.Thousand-grain weight, grain protein yield, and test weight reduced significantly underboth salinity and drought stress conditions. Protein content showed positive correla-tion with wet gluten, dry gluten, SDS sedimentation, and volume and strong negativecorrelation with other traits. It is concluded that influence of salinity stress was greaterthan drought stress on grain protein yield and some other grain-quality-related traits.

Keywords Drought, durum wheat, grain quality, saline field, salt tolerance

Introduction

Breeding for the development of cultivars with economical production for the regionsunder environmental stress is one of the most important challenges in Iran. Drought andsalinity are the major adverse environmental factors that prevent plants from realizingtheir full genetic potential and are primary constraints in the durum-wheat-producing area,which are particularly arid and semi-arid areas of world. Considerations of the possibleincrease of the intensity and frequency of droughts due to global climate change and acurrent estimate of 47% of the drought-stress-affected land in arid and semi-arid regions, acomprehensive understanding of the effect of drought on plant attributes becomes a basicrequirement to aid water, land, and genetic resources management. A similar inferencecould be drawn for salinity, considering worldwide up to 47% (13% severely and 34%moderately) of the arable irrigated land in arid and semi-arid regions is affected by salinity(FAO 2012).

Received 24 January 2012; accepted 17 March 2013.Address correspondence to S. Houshmand, Department of Plant Breeding and Biotechnology,

College of Agriculture, Shahrekord University, Shahrekord, P. O. Box 115, Iran. E-mail:s_hoshmand@yahoo.com; Houshmand@agr.sku.ac.ir

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World markets demand high-quality durum wheat [Triticum turgidum L. subsp. durum(Desf.) Husn.]. Hence, breeding and production for acceptable end-use quality has becomean important issue for breeders and farmers of durum wheat. Protein content, yield, andgluten quantity and quality are the most important variables in determining pasta quality.Protein composition and sodium dodecyl sulfate (SDS) sedimentation volume are used topredict gluten quality of wheat. The SDS sedimentation volume is an index widely usedto evaluate flour quality in durum wheat and it commonly used as an indicator of glutenquality (strength). High test weight and large grains are important traits in world marketsbecause they generally indicate sound grain with high flour yield.

Environmental conditions such as salt and drought stress are known to have signifi-cant influence on durum wheat quality. Francois et al. (1986) have reported that salt stressafflicts plant agriculture with decreasing the grain yield and increasing the protein content.Drought stress increased mainly protein content and reduced thousand-grain weight basedon a study on 10 durum wheat genotypes under field conditions by Rharrabti et al. (2003).Katerji et al. (2005) studied salt-tolerant and salt-sensitive varieties grown in lysimeterconditions and reported that salinity had a slight positive effect on the grain quality ofthe salt-tolerant genotypes, whereas the grain quality of salt sensitive genotypes was notaffected by the salinity.

Genotypic variation for salt tolerance has been reported in durum wheat (Houshmandet al. 2005; Katerji et al. 2005; Munns et al. 2000) and field evaluation of salt tolerance indurum wheat genotypes has been the objective of a few studies (Houshmand et al. 2005;Katerji et al. 2005). It should be also mentioned that drought stress was applied at the repro-duction stage while salinity stress was implemented for the more or less whole life cycle ofthe plant. A somewhat similar situation (the period of stresses) existed in the farmers’fields. However, in spite of a few reports focusing on the effect of drought (Rharrabtiet al. 2003; Gooding et al. 2003) or salinity stress (Francois et al. 1986; Katerji et al.2005; Borrelli et al. 2011) on grain quality, little information is available on the effects ofthese two major abiotic stresses on grain-quality-related traits in wheat genotypes havinga common genetic background grown under farmers’ conditions. In the present study, theinfluences of drought and salinity stresses on grain-quality-related traits were investigatedusing a common set of durum-wheat genotypes differing in salinity tolerance.

Materials and Methods

Plant Materials

Eight durum wheat genotypes including three salt-tolerant genotypes and one salt-sensitivegenotype derived from in vitro assessment (Arzani and Mirodjagh 1999) and three salt-tolerant genotypes and one salt-sensitive genotype derived from a two-year saline fieldexperiment were used. In vitro salt-tolerant genotypes (ITGs) were Dipper-6, Prion-l, andPI40100; the in vitro salt-sensitive genotype (ISG) was Massara-1. Field selected salt-tolerant genotypes (FTGs) were Ajaia/Hora/Jro/3/Gan (Aj/. . ./Gan), Srn/Vic, PI40098,and and the field selected salt-sensitive (FSG) genotype was Lund-6.

Field Experiments

Three separate field experiments including no stress, drought stress, and salt stress duringtwo growing seasons at two sites were conducted. The first two were conducted at theresearch farm of Isfahan University of Technology located at Lavark, Iran (40 km south-west of Isfahan, 32◦ 32′ N and 51◦ 23′ E, 1630 m asl) having a Haplargids soil type of

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Effects of Salinity and Drought on Grain Quality 299

the arid tropic. The saline field located at the Agricultural-Saline Research ExperimentStation, Rodasht (65 km east of Isfahan, 32◦ 29′ N and 52◦ 10′ E, 1560 m asl) with salinesoil (described as a Haplic Solonchaks) and irrigated with saline water. This research sta-tion is situated close to the Great Salt Desert (also locally known as Dasht-e Kavir), whichis a large desert in the middle of the Iranian plateau. Further details about the Rodasht areacan be found in Droogers et al. (2000).

The surface layer (0 to 30 cm deep) of both soils had a silty clay loam texture. Thenonsaline field had pH of 7.3–7.8 and electrical conductivity (EC) of 1.1–1.2 dS m−1

and contained 1.3% of organic matter, and the saline field had pH of 7.6–8.0 and EC of3.3–3.8 dS m−1 and contained 0.9% organic matter. Mean annual precipitation and meanannual temperature were similar, 140 mm and 15 ◦C, respectively, at the nonsaline andsaline fields. At the nonsaline field, irrigated water with an EC of 1 dS m−1 was used forboth no-stress and drought stress experiments.

Drought stress was applied by ceasing the irrigation at the flowering. Two moistureregimes of irrigation after 70 mm evaporation from class-A pan corresponded to soil waterpotential of –0.5 MPa (no stress) and irrigation after 130 mm evaporation from class-A pancorresponded to soil water potential of –1.0 MPa (drought-stress) were applied.

In the saline field experiment, plants were irrigated with nonsaline water (ECw =2 dS m−1) to the three-leaf stage (Zadoks 13) and saline water (ECw = 10 dS m−1) after-ward. Soil samples were taken at 15-cm increments to a depth of 30 cm in each plot, 2 daysafter irrigations and just before harvest during both years. Average EC values were deter-mined on saturated-soil extracts (ECe). Although the ECe at the nonsaline soil ranged from1.4 to 1.8 dS m−1, they varied from 2.5 to 8.5 dS m−1 at the first and the last irrigation atthe saline soil, respectively.

A randomized complete block design with three replications was used at each of exper-iments within each year. Each plot consisted of five 6-m long rows spaced 20 cm apart.Fertilizers were applied prior to sowing at a rate of 50 kg nitrogen (N) ha−1 and 30 kgphosphorus (P) ha−1, and additional side dressing of 50 kg N ha−1 was applied at the earlysquare stage (floral buds).

Grain Quality Traits

Grain-quality-related traits including grain protein content, grain protein yield, 1000-grainweight, test weight, wet and dry gluten content, and SDS sedimentation volume were eval-uated for each plot in the three experiments. Thousand-grain weight was determined using10 samples of 1000 grains for each plot. Grain protein content was determined by Kjeldahlmethod (N × 5.7, 14% moisture basis). Grain protein content was multiplied to grain yieldper m−2 to determine the grain protein yield. Sodium dodecyl sulfate (SDS) sedimenta-tion volume was determined according to Preston, March, and Tipples (1982). Wet and drygluten contents were measured according to Approved Method 38-12 (AACC 1995).

Statistical Analyses

A separate analysis of variance (ANOVA) was conducted for each of the field experiments.Combined ANOVA was performed for grain quality traits over the three experiments and2 years after verifying the homogeneity of trial variance errors using Bartlett’s test at the5% probability level. Analysis of variance was carried out using PROC GLM of SASsoftware (SAS Institute 1997).

Mean comparisons were conducted using Fisher’s least significant differences (LSDs).Pairwise mean comparisons of ITGs vs ISG, FTGs vs FSG, ITGs vs FTGs, and total

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salt-tolerant genotypes (TGs) vs total sensitive genotypes (SGs) were done by ANOVAorthogonal (independent) comparisons. Pearson correlation coefficients were used to deter-mine the relationships between grain yield and the tested quality traits at the separate fieldexperimental conditions and their combined data. Stepwise-regression analyses were usedto determine the impact of grain quality traits as dependent variables on grain proteincontent and grain protein yield as independent variables.

Results and Discussion

Results of ANOVAs for each of the three experiments showed that genotypes variedsignificantly for the grain-quality-related traits. Combined analysis of variance indicatedthe stresses (salinity and drought) significantly affected the traits (Table 1). Genotype ×stress interaction was significant for 1000-grain weight (P ≤ 0.05), grain protein yield(P ≤ 0.01), wet gluten content (P ≤ 0.01), test weight (P ≤ 0.01), and SDS sedimenta-tion volume (P ≤ 0.01). The significant genotype × stress interactions show that differentdurum wheat genotypes respond differently to various environmental conditions (normal,drought, and salinity). The effects of year and year × genotype were not significant for thetested grain quality traits (Table 1) and hence mean comparisons of these traits carried outusing the averages of 2-year data.

Table 2 shows mean comparisons of genotypes for grain protein content and grainprotein yield under no-stress (control), drought, and salt-stress field conditions. Proteincontent ranged from 117 g kg−1 [Lund-6 (FSG)] to 138 g kg−1 [Massara-1 (ISG)] at no-stress field conditions (control). Both drought and salt stresses caused significant increaseof grain protein content with average increases of 15.8 g kg−1 (12%) and 23.6 g kg−1

(18%), respectively. Cultivar Lund-6 (FSG) possessed the greatest increase in protein

Table 1Combined analysis of variance of durum grain quality traits evaluated under normal,

salinity, and drought stress conditions in two yearsa,b

Mean squareSource ofvariation df GW PC PY WG DG TW SDSV

Stress (S) 1 6447∗∗ 6940∗∗ 28277∗∗ 121168∗∗ 13264∗∗ 23083∗∗ 3598∗∗Year (Y) 2 0.35ns 4.01ns 0.52ns 28.02ns 7.58ns 51.41ns 0.07ns

Y × S 2 121∗∗ 3.04ns 0.37ns 171.3∗∗ 4.42ns 34.32ns 111.2∗∗Error1 12 0.08 0.88 0.13 6.53 2.08 12.05 0.02Genotype (G) 7 77∗ 324∗∗ 1062∗∗ 40507∗∗ 2697∗∗ 7851∗ 161∗∗G × Y 7 54.12ns 121.6ns 12.1ns 2146ns 1153ns 1218ns 46.5ns

G × S 14 57.6∗ 103.4ns 760.4∗∗ 12908∗∗ 1642ns 3972.9∗∗ 95.7∗∗G × Y × S 14 41.6ns 86.1ns 391.9∗∗ 23311∗∗ 765.1ns 1101ns 35.4ns

Error2 84 30.04 58.12 6.45 1514.6 940.3 967.2 24.3

aGW, 1000-grain weight; PC, grain protein content; PY, grain protein yield; WG, wet glutencontent; DG, dry gluten content; TW, test weight; SDSV, SDS sedimentation volume.

bns, nonsignificant.∗P ≤ 0.05.∗∗P ≤ 0.01.

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Effects of Salinity and Drought on Grain Quality 301

Table 2Means of grain protein content and grain protein yield and contrast mean square of in

vitro and field experiments assessment of durum wheat genotypes under no stress(normal), drought stress, and salinity stress field conditions

Grain protein content (g kg−1) Grain protein yield (g m−2)

Genotype No

stre

ss

Dro

ught

stre

ss

Salt

stre

ss

No

stre

ss

Dro

ught

stre

ss

Salt

stre

ss

Prion-1 (ITG) 130.7 143.9 153.6 94.3 31.8 28.2Dipper-6 (ITG) 127.8 147.9 147.1 81.0 32.2 28.8PI40100 (ITG) 135.7 152.9 163.5 36.5 23.5 17.6Massara-1 (ISG) 137.8 147.2 153.6 88.1 37.7 18.8Srn/Vic (FTG) 135.7 139.1 160.1 74.7 30.3 29.8PI40098 (FTG) 135.6 149.6 154.0 66.4 28.9 22.5Aj/. . ./Gan (FTG) 131.7 147.3 155.7 56.2 22.2 28.0Lund-6(FSG) 117.0 150.7 153.5 58.3 44.9 21.9Total mean 131.5 147.3 155.1 69.6 31.5 24.5LSD (5%) 20.8 21.2 13.1 14.1 11.5 7.8

Orthogonal mean comparisonsITGs vs ISG −6.40ns 1.03ns 1.13ns −17.50∗∗ −8.53ns 6.07ns

FTGs vs FSG 17.33∗ −5.37ns 3.10ns 7.47ns −17.77∗∗ 4.87ns

ITGs vs FTGs −2.93ns 2.90ns −1.87ns 4.83ns 2.03ns −1.90ns

TGs vs SGs 5.47ns −2.17ns 2.12ns −5.02ns −13.15∗∗ 5.47∗

Notes. LSD5% = 8.2 g kg−1 and 3.1 g m−2 for grain protein content and grain protein yield, respec-tively, for comparing genotypic means in the three environmental conditions. ns, nonsignificant.

∗Significant at 0.05 probability level.∗∗Significant at 0.01 probability level.

content due to both drought (33.7 g kg−1 = 28.8%) and salt (36.5 g kg−1 = 31.2%)stresses.

Grain protein yield significantly (P ≤ 0.01) decreased both salinity and droughtstresses for all genotypes. The impact of salt stress was greater than drought stress inreducing grain protein yield where 70 g m−2 mean of grain protein yield at control experi-ment reduced to 31 g m−2 (54.7% reduction) and 24.5 g m−2 (64.8% reduction) at droughtand salt stress experiments, respectively. Total salt-tolerant genotypic mean (TGs) wassignificantly superior than total sensitive genotypes mean (SGs) at both stressed environ-mental conditions for grain protein yield (Table 2). FTGs vs FSG did not significantlyvary for grain protein content at both salinity- and drought-stress conditions, and thus theirgrain yield disparity could be explained by differences between tolerance and sensitivegenotypes for grain yield. Comparison between tolerant and sensitive genotypes to salinity(TGs vs SGs) for grain protein yield revealed that tolerant and sensitive genotypes selectedunder salinity conditions necessarily do not possess identical response in drought-stressconditions.

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302 S. Houshmand, A. Arzani, and S. A. M. Mirmohammadi-Maibody

Orthogonal mean comparisons of ITGs vs ISG, FTGs vs FSG, ITGs vs FTGs, andTGs vs SGs for grain protein content revealed a nonsignificant difference between thesepair genotypic groups with the exception of FTGs vs FSG (P ≤ 0.05) under normalfield conditions (Table 2). Comparisons of different genotypic groups for grain proteinyield indicated that ITGs vs FTGs did not significantly differ at no-stress and stress con-ditions, whereas ITGs differed with ISGs at no-stress experiment and FTGs vs FSGsdiffered at drought-stress experiment. The overall results of orthogonal means compari-son for the grain quality traits of in vitro– and field-selected salt-tolerant and salt-sensitivedurum wheat genotypes demonstrated that genotypes that were selected based on grainyield under field conditions or based on callus production under in vitro conditionsdid not follow same trend of responses for grain quality traits even under saline fieldconditions.

Salt tolerance in plant species is thought to operate at the cellular level, and glyco-phytes are believed to have special cellular mechanisms for salt tolerance (Mansour andSalama 2004). Hence, the comparable performance of grain protein content and grainprotein yield of in vitro–selected salt-tolerant genotypes (ITGs) with that of field-selectedsalt-tolerant genotypes (FTGs) under both drought and salinity stress conditions couldbe explained by the involved cellular mechanisms (Table 2). No significant relationshipbetween performance of the genotypes under normal and stressed field conditions wasobserved for the protein content. Likewise, there was not any relationship between stressconditions (drought and salt) against normal conditions for grain protein yield (data notshown).

Thousand-grain weight of the tested genotypes was significantly reduced underboth drought and salt stress conditions compared to normal field conditions (Table 3).Nevertheless, the reduction due to salt stress was more than drought stress. Drought stressreduced the genotypic means of 1000-grain weight from 44.5 g at normal field conditions to31.3 g (29.7% reduction), whereas it was reduced to 21.4 g (51.9% reduction) under salinefield conditions. Moreover, genotypes differed in the magnitude of decrease in 1000-grainweight in response to drought and salt stress.

In comparison with normal conditions, the reduction of test weight genotypicmeans due to drought and salt stresses were 10.3% and 17.5%, respectively (Table 3).These reductions were less than the reduction of grain protein yield and 1000-grainweight, which indicate different response of the traits to drought and salinity stresses.Comparison test weight of salt-tolerant genotypes versus salt-sensitive genotypes showedthat the former has better performance under both normal and saline field condi-tions.

Thousand-grain weight and test weight of the tested genotypes was significantlyreduced under both drought and salt stress conditions compared to normal field condi-tions (Table 3). Decline of 1000-grain weight due to water deficit in bread wheat (Dencicet al. 2000) and durum what (Garcia del Moral et al. 2003; Rharrabti et al. 2003) werepreviously reported. On the other hand, both significant reduction of 1000-grain weight(Francois et al. 1986) and nonsignificant effects (Katerji et al. 2009) of salinity stress indurum wheat have been reported. Grain weight may be reduced under the stress condi-tions possibly because of reduced photosynthetic assimilation and nitrogen available forredistribution during grain filling.

Genotypic means for wet and dry gluten contents ranged from 407 to 541 g kg−1 and153 to 187 g kg−1 under normal field conditions, respectively (Table 4). Under normalfield conditions Massara-1 (ISG) and PI40100 (ITG) produced the lowest and highest ofgluten content, respectively. Drought stress increased wet and dry gluten of all genotypes,

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Effects of Salinity and Drought on Grain Quality 303

Table 3Means of grain weight and test weight and contrast mean square of in vitro and fieldexperiments assessment of durum wheat genotypes under no stress (normal), drought

stress, and salinity stress field conditions

1000-grain weight (g) Test weight (kg m−3)

Genotype No

stre

ss

Dro

ught

stre

ss

Salt

stre

ss

No

stre

ss

Dro

ught

stre

ss

Salt

stre

ss

Prion-1 (ITG) 44.8 29.9 16.6 778 686 619Dipper-6 (ITG) 41.2 28.5 21.7 804 724 669PI40100 (ITG) 39.3 32.6 27.6 806 698 682Massara-1 (ISG) 44.4 29.2 17.8 783 691 571Srn/Vic (FTG) 47.7 31.9 23.8 794 730 673PI40098 (FTG) 42.2 29.0 21.5 743 681 696Aj/. . ./Gan (FTG) 47.8 31.2 22.5 772 697 631Lund-6(FSG) 48.5 38.0 19.9 814 742 652mean 44.5 31.3 21.4 787 706 649LSD (5%) 7.4 6.9 7.0 39 37 55

Orthogonal mean comparisonsITGs vs ISG −2.63ns 1.13ns 4.17ns 13.00ns 11.67ns 85.67∗∗FTGs vs FSG −2.60ns −7.30∗ 2.70ns −44.33∗∗ −39.33∗∗ 14.67ns

ITGs vs FTGs −4.13ns −0.37ns −0.63ns 26.33∗ 0.00ns −10.0ns

TGs vs SGs −2.62ns −3.08ns 3.43ns −15.67ns −13.83ns 50.17∗∗

Notes. LSD5% = 2.4 g and 30.3 Kg m−3 for grain weight and test weight, respectively, forcomparing genotypic means in the three environmental conditions.ns, nonsignificant.

∗Significant at 0.05 probability level.∗∗Significant at 0.01 probability level.

whereas salt stress either increased or decreased genotypic means of wet and dry glutencontents. The orthogonal comparisons of different genotypic groups for wet and dry glutendid not prove to be significant (Table 4). Overall wet and dry gluten content of genotypesincreased by both drought and salt stresses, although the increased due to the former wasmore substantial (Table 4). This can be explained by the effects of drought and salinitystress on photosynthetic capacity in wheat plant in terms of changes in the sink–sourcebalance, in favoring carbon (C) assimilate.

The greatest increase to the related grain quality traits due to stress belonged to SDSsedimentation volume, where 26.0 ml mean of SDS sedimentation volume at no-stresscondition increased to 34.0 ml (31% increase) to 43.3 ml (66% increase) at drought-and salt-stress experiments, respectively (Table 4). Therefore, SDS sedimentation volume,as indirect index of gluten quality (protein composition), has been strongly affected bydrought and salinity stresses (Table 4). The results of the present study are consistent withthose of Rharrabti et al. (2003) in durum wheat and those of Gooding et al. (2003) in breadwheat. Rharrabti et al. (2003) tested 10 durum wheat genotypes at different field sites and

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Table 4Means of wet gluten content, dry gluten content, and SDS sedimentation volume and

contrast mean square of in vitro and field experiments assessment of durum wheatgenotypes under no stress (normal), drought stress, and salinity stress field conditions

Wet gluten content(g kg−1)

Dry gluten content(g kg−1)

SDS sedimentationvolume (ml)

Genotype Non

stre

ss

Dro

ught

stre

ss

Salt

stre

ss

Non

stre

ss

Dro

ught

stre

ss

Salt

stre

ss

Non

stre

ss

Dro

ught

stre

ss

Salt

stre

ss

Prion-1 (ITG) 436 590 408 163 209 167 25.2 42.4 47.4Dipper-6 (ITG) 425 475 363 166 173 147 30.6 32.8 41.5PI40100 (ITG) 541 659 541 187 226 206 25.4 36.3 38.0Massara-1 (ISG) 407 552 509 153 194 183 19.3 28.7 39.9Srn/Vic (FTG) 437 448 541 167 169 203 31.5 35.8 47.4PI40098 (FTG) 448 552 441 163 213 177 26.2 28.6 43.8Aj/. . ./Gan (FTG) 516 586 502 182 221 191 23.0 38.2 49.2Lund-6(FSG) 434 523 433 154 194 165 26.9 29.0 38.8Mean 456 548 467 167 200 180 26.0 34.0 43.3LSD (0.5%) 85 72 79 29 33 38 3.5 6.1 6.5

Orthogonal mean comparisonsITGs vs ISG 60.3ns 22.7ns −71.7ns 19.0ns 8.7ns −9.7ns 7.8∗∗ 8.5ns 2.4ns

FTGs vs FSG 33.0ns 5.7ns 61.7ns 16.7ns 7.0ns 25.3ns 0.0ns 5.2∗ 8.0∗∗ITGs vs FTGs 0.30ns 46.0 −57.3ns 1.3ns 1.7ns −17.0ns 0.2ns 2.9ns −4.5ns

TGs vs SGs 46.7ns 14.2ns −5.0ns 17.8ns 7.8ns 7.8ns 3.9∗∗ 6.8∗∗ 5.2∗

Notes. LSD5% = 22.3 g kg−1, 12.6 g kg−1, and 1.1 ml for wet gluten content, dry gluten con-tent, and SDS sedimentation volume, respectively, for comparing genotypic means in the threeenvironmental conditions. ns, nonsignificant.

∗Significant at 0.05 probability level.∗∗Significant at 0.01 probability level.

observed greater SDS sedimentation volume under rainfed conditions compared to thatproduced under the irrigated condition.

Orthogonal comparisons indicated that in vitro– and field-selected genotypes showvarious responses related to SDS sedimentation volume at different environmental con-ditions (Table 4) and SDS sedimentation volume of ITGs was significantly greater thanthat of ISG at only normal experiment. However, there was no significant differencebetween the means of FTGs and FSG at normal for this trait whereas they significantlydiffer at both stress experimental conditions. Overall, the tolerant genotypes possessedgreater SDS sedimentation volume than sensitive genotypes at the three experimentalconditions.

Drought and salinity stresses positively influenced grain protein content, glutencontent, and SDS sedimentation volume traits (Tables 2 and 4). These results are consistent

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Effects of Salinity and Drought on Grain Quality 305

with those of Rharrabti et al. (2003), who found the positive effect of drought stress on pro-tein content. Our results are also consistent with that of Francois et al. (1986) and Borrelliet al. (2011), who observed the positive effect of salinity stress on protein content of durumwheat genotypes. However, Katerji et al. (2005) reported that the protein contents of durumwheat genotypes were not significantly influenced by salinity stress.

According to the results of the present study it could be concluded that influence ofsalinity stress was greater than drought stress on grain protein yield and some other grain-quality-related traits. Distinctions between the osmotic levels as a common mechanism ofsalinity and drought stress and salt-specific effect of salinity have already been emphasized(Munns et al. 2002).

Correlation coefficients calculated between grain yield and grain quality traits at thethree environmental conditions and their combined data presented in Tables 5 and 6.Among studied grain quality traits, grain protein yield, and 1000-grain weight showed high(0.94∗∗ ≥ r ≥ 0.98∗∗) and moderate (0.29∗ ≤ r ≥0.73∗∗) positive correlations with grainyield under normal field conditions and means of normal, salinity, and drought conditions(Table 5). A negative relationship was observed between grain yield and grain-quality-related traits including grain protein content, wet gluten content, dry gluten content, andSDS sedimentation volume at normal field conditions (Table 5). The inverse relation-ships between grain yield and grain quality are often exacerbated by both drought andsalt stresses conditions (Table 6).

At the three experimental conditions protein content, wet gluten content, dry glutencontent, and SDS sedimentation volume showed positive correlation with each other andnegative correlation with grain protein yield, 1000-grain weight, and test weight (Tables 5and 6). Although the stresses in some cases intensified these correlation coefficients,there was discrepancy between the two stress conditions. For example, the correlationcoefficient of test weight and dry gluten content (r = −0.54) was highly significant(P ≤ 0.01) at drought stress condition, but it was too low and nonsignificant (r = −0.06) at

Table 5Pearson correlation coefficients between the grain yield and grain quality traits evaluated

under normal field conditions (above the diagonal) and mean of normal, salinity, anddrought stress conditions (below the diagonal)a,b

GY GW PC PY WG DG TW SDSV

GY — 0.36∗ −0.11ns 0.94∗∗ −0.56∗∗ −0.44∗∗ 0.02ns −0.05ns

GW 0.73∗∗ — −0.41∗∗ 0.11ns −0.10ns −0.21ns 0.09ns −0.01ns

PC −0.65∗∗ −0.66∗∗ — 0.24ns 0.23ns 0.31∗ −0.25ns 0.04ns

PY 0.98∗∗ 0.76∗∗ −0.52∗∗ — −0.48∗∗ −0.33∗ −0.13ns −0.04ns

WG −0.37∗∗ −0.06ns 0.32∗∗ −0.34∗∗ — 0.86∗∗ −0.11ns 0.12ns

DG −0.45∗∗ −0.19∗ 0.42∗∗ −0.42∗∗ 0.91∗∗ — −0.06ns 0.23ns

TW 0.72∗∗ 0.80∗∗ −0.63∗∗ 0.69∗∗ −0.18∗ −0.29∗∗ — 0.32ns

SDSV −0.66∗∗ −0.78∗∗ 0.59∗∗ −0.63∗∗ 0.13ns 0.27∗∗ −0.68∗∗ —

aGY, grain yield; GW, 1000-grain weight; PC, grain protein content; PY, grain protein yield; WG,wet gluten content; DG, dry gluten content; TW, test weight; and SDSV, SDS sedimentation volume.

bns, nonsignificant.∗P ≤ 0.05.∗∗P ≤ 0.01.

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306 S. Houshmand, A. Arzani, and S. A. M. Mirmohammadi-Maibody

Table 6Pearson correlation coefficients between the grain yield and grain quality traits evaluated

under drought stress (above the diagonal) and salt stress (below the diagonal)conditionsa,b

GY GW PC PY WG DG TW SDSV

GY — 0.30∗ −0.14ns 0.97∗∗ −0.40∗∗ −0.47∗∗ 0.41∗∗ −0.36∗GW 0.29∗ — 0.10ns 0.31∗ 0.03ns 0.09ns 0.33∗ −0.13ns

PC −0.22ns 0.22ns — 0.22ns 0.44∗∗ 0.38∗∗ −0.34∗ 0.09ns

PY 0.97∗∗ 0.05ns −0.02ns — −0.29∗ −0.35∗ 0.33∗ −0.56∗∗WG −0.32∗ 0.25ns 0.42∗∗ −0.22ns — 0.91∗∗ −0.47∗∗ 0.33∗DG −0.33∗ 0.19ns 0.47∗∗ −0.21ns 0.91∗∗ — −0.54∗∗ 0.24ns

TW 0.19ns 0.37∗ 0.16ns 0.21ns −0.11ns −0.06ns — −0.19ns

SDSV −0.42∗∗ −0.32∗ 0.13ns 0.47∗∗ 0.17ns 0.29∗ −0.05ns —

aGY, grain yield; GW, 1000-grain weight; PC, grain protein content; PY, grain protein yield; WG,wet gluten content; DG, dry gluten content; TW, test weight; and SDSV, SDS sedimentation volume.

bns, nonsignificant.∗P ≤ 0.05.∗∗P ≤ 0.01.

salt stress conditions. There was also a small correlation coefficient between some ofthe traits in some environmental conditions such as the relationship of test weight andSDS sedimentation volume with other traits at salinity or drought stress environments(Table 6).

To explain the contribution of the tested grain quality traits to the grain protein contentat each of experimental conditions, a stepwise regression analysis was used (Table 7).The tested traits that played a role in inducing variations of grain protein content and grainprotein yield were not consistent among the three experimental conditions. Thousand-grainweight alone could justify approximately 17% of grain protein content variation underno-stress experiment. At drought-stress conditions wet gluten content and grain proteinyield with cumulative R2 = 0.33 and at salt-stress conditions dry gluten content (R2 =0.22) could significantly contribute to explain grain protein content variation. Explicatortraits for grain protein yield also varied at each of experimental conditions (Table 7). At saltstress conditions, SDS sedimentation volume, dry gluten content, and 1000-grain weightwere the traits that contributed to grain protein yield with cumulative R2 = 0.49. Overall,when data were combined across the three experiments, 1000-grain weight with dry glutencontent accounted for more than half of protein content and protein yield variations. In thissituation the variation to both traits contributed by 1000-grain weight was greater due todry gluten content.

Comparison of two groups of tolerant and sensitive genotypes for 1000-grain weightrevealed the nonsignificant differences with the exception of FTGs vs FSG (P ≤0.05) under drought-stress conditions (Table 3). The results of this study are in agree-ment with those of Katerji et al. (2005), who reported a nonsignificant difference betweensalt-tolerant and salt-sensitive genotypes in response to salt stress for 1000-grain-weighttrait. However, with consideration of the coefficient signs in the regression model pre-sented in Table 7, it is suggested that early selection of breeding lines with respect togreater 1000-grain weight should help breeders to improve cultivars with superior proteinyield values.

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Effects of Salinity and Drought on Grain Quality 307

Table 7Contributions of grain quality related traits to variation in grain protein content and grain

protein yield under the three experiment conditions using stepwise regressiona

Dependenttrait Experiment

Includedtraits F value R2b Model

PC No stress GW 4.8∗ 0.17 174.8 − 0.97GWDrought stress WG 5.34∗ 0.19 93.6 + 0.07 WG + 0.44 PY

PY 4.16∗ 0.33Salt stress DG 6.95∗∗ 0.22 129.6 + 0.14 DGTotal mean GW 54.11∗∗∗ 0.44 141.0 − 0.79 GW + 0.16 DG

DG 13.42∗∗∗ 0.53

PY No stress WG 6.54∗∗ 0.23 60.2 − 0.16 GW + 0.63 PCPC 4.37∗ 0.36

Drought stress DG 4.27∗ 0.13 −0.95–0.18 DG + 0.33 PC +0.63 GW

PC 6.42∗∗ 0.28GW 4.21∗ 0.38

Salt stress SDSV 6.44∗∗ 0.23 −2.5 + 0.85SDSV − 0.11DG+ 0.49GW

DG 4.56∗ 0.36GW 5.11∗ 0.49

Total mean GW 96.55∗∗∗ 0.58 28.5 + 1.65GW − 0.08 DGDG 18.11∗∗∗ 0.67

aPC, grain protein content; PY, grain protein yield; GW, 1000-grain weight; WG, wet glutencontent; DG, dry gluten content; and SDSV, SDS sedimentation volume.

bR square is cumulative when more than one trait considered in the model.∗P ≤ 0.05.∗∗P ≤ 0.01.∗∗∗P ≤ 0.001.

Conclusions

In the arid and semi-arid regions, plant breeders tackle a dilemma in selecting materialsfor both normal and salinity/drought conditions because it is often difficult to undertakethe parallel breeding programs representing the target environments. Nevertheless, in thepresent study, there was some discrepancy for the relationship between grain quality traitsunder drought and salinity stress conditions (Table 6). This finding, together with thegreater effects of salinity than drought stress on grain protein yield and some of grain-quality-related traits, suggests that wheat breeders confront serious challenges to developsuperior cultivars with a broad spectrum of abiotic resistance.

Overall, it can be concluded that wheat breeders should not only conduct selection forthese two economically important traits (yield and quality) at the target environments butalso make an acceptable compromise between two opposing selective traits.

Acknowledgment

The technical assistance from B. Bahrami at Laboratory of Food Technology is gratefullyacknowledged.

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