Printer Friendly

Screening and Selection of Synthetic Hexaploid Wheat Germplasm for Salinity Tolerance Based on Physiological and Biochemical Characters.

Byline: Ali Raza Gurmani Sami Ullah Khan Fazli Mabood Zahoor Ahmed Shahid Javed Butt Jalal-Ud Din Abdul Mujeeb-Kazi and Donald Smith

Abstract

Salinity is one of the major abiotic stresses affecting plant growth and development as salinization of cultivated land is increasing globally. There is considerable variation in salinity tolerance of wheat genotypes and selection of salt tolerant genotypes is of great interest in salt affected regions. An experiment was conducted to evaluate the salt tolerance of 13 newly developed synthetic hexaploid wheats (2n=6x=42; AABBDD) along with two check varieties Kharchia-65 and Shorawaki.Thirteen-day-old seedlings grown in a hydroponics system were subjected to 0 75 and 150 mM NaCl in Hoagland's nutrientsolution for five days. Increasing salt stress generally affected all physiological aspects of the plants; however various enzymeactivities proline content soluble sugars and protein content increased with increased salt concentration. Exposure to salt stress affected plant dry biomass of all the genotypes; however there was a difference in response of wheat genotypes to salinity stress. Among the tested genotypes Kharchia-65 Shorawaki N-7 N-9 and N-13 showed better performance in terms of plant biomass K+: Na+ ratio chlorophyll content net assimilation rate (A) transpiration rate (E) and stomatal conductance (gs). There was a strong correlation between K+:Na+ ratio chlorophyll proline SOD CAT and gs against shoot dry biomass. Based on overall performance the tested wheat genotypes were grouped as tolerant moderately tolerant and sensitive. Wheat genotypes N-7 N-9 and N-13 were grouped as tolerant N-33 and N-12 as moderately tolerant and the remaining genotypes were found sensitive to salt stress. In this regard K+:Na+ ratio chlorophyll proline SOD CAT and gs may be used as potential biochemical and physiological selection criteria for screening of salt tolerance in wheat genotypes. Copyright 2014 Friends Science Publishers

Keywords: Plant biomass; Physiological and biochemical attributes; Salt stress; Synthetic hexaploid wheat

Introduction

Wheat (Triticum aestivum L.) is an important cereal crop and a source of staple food for many countries. Wheat yield is reduced by abiotic stresses such as salinity drought and heat in arid and semi arid regions of the world (Zhang et al.2010; Farooq et al. 2011 2013 2014). Of these abiotic stresses salinity is one of the major stresses regarded as highly deleterious to the growth and productivity of wheat crop (Zhang et al. 2010; Wakeel et al. 2011; Jafar et al.2012). Salt effected soils can be brought under cultivation by producing salt tolerant germplasm. This involves identification of wheat gemplasm on the basis of physiological and biochemical traits that are tolerant to salinity or using new genetic resources to introduce new genes for salt tolerance into existing cultivars (Farshadfar et al. 2008). A method of introducing novel genes into hexaploid bread wheat is through synthetic hexaploidwheats via bridge crossing which are produced from interspecific crosses between tetraploid Triticum turgidum L. (2n=4x=28; AABB) and diploid Aegilops tauschii (Coss) Schmal. (2n=2x=14; DD) as described by Mujeeb-Kazi et al. (1996). The salinity tolerance trait present in D-genome diploid ancestor of wheat (Ae. tauschii) is potentially transferable to synthetics when this donor is crossed with susceptible durum parents (Trethowan and Mujeeb-Kazi2008).Salinity stress affects plant growth and development at all levels. In wheat salinity decreases pant growth due to osmotic effect and accumulation of excessive concentrations of Na+ and Cl- and consequently declines in the availability of assimilates to growing tissues and organs (Munns 2007). Elevated Na+ level in plant tissue may harm membranes and organelles and ultimately affect growth (Hussain et al.2013). Thus less Na+ uptake and higher K+:Na+ ratios in plant tissue has well correlated with salt tolerance (Flowers 2004). A reduction in photosynthetic pigments due to toxic level of Na+ in plant tissue under saline conditions has been reported in various plant species (Ashraf and Harris 2013). Excess cellular Na+ and Cl- impair the electron transport system and accelerate the production of reactive oxygen species (ROS) (Foyer et al. 1994). Elevated ROS inside cells is highly injurious to membranes and other cellular components including chloroplasts proteins nucleic acids and lipids. In order to combat excessive intercellular ROS plants have developed antioxidant defense systems assisting them in managing ROS levels. Plants employ various mechanisms to protect themselves from the adverse effects of salinity. Plants respond to salinity stress by accumulating proline and sugar; these act as osmoprotectants against saltinjury to plants (Din et al. 2008; Gurmani et al. 2013). Salinity also affects photosynthetic performance of plants such as net assimilation rate transpiration rates stomatal conductance and water use efficiency (Ashraf 2004). Variation in gas exchange attributes not only prevail in different species but within cultivars of the same species. Therefore gas exchange traits may be employed as screening parameters for salt tolerance; where a positive correlation exist between growth and gas exchange attributes (Ashraf 2004).In order to assess the salinity tolerance of plants physiological and biochemical parameters are used to evaluate genotypic variation for salinity tolerance in various crop species (Ahmadi and Ardekani 2006; Munns 2007). Researchers have emphasized inorganic ions organic metabolites water relations and photosynthesis as important variables for salinity tolerance in plants (Ashraf 2004). Plants subjected to salinity stress produce several metabolites that differ widely among species and even between genotypes (Flowers 2004; Munns 2007). Screening for salinity tolerance can done under saline field conditions in an appropriate growing season (SamMons et al. 1978); however greenhouse based studies to screen for salinity tolerant plant types can also be conducted. One of the limitations of field studies is the heterogeneity of the field conditions since salinity varies in patches under field conditions. On the other hand it is relatively easy to maintain and control various salinity levels under controlled environment conditions so that greenhouse studies are generally preferred over field for screening of salinity tolerance in crop plants (Munns and James 2003).There is considerable genetic diversity in crop plants for salinity tolerance and a number of studies have focused on this in various crops such as rice (Hussain et al. 2013) Canola (Ahmadi and Ardekani 2006) cotton (Shaheen et al. 2012) and wheat (Munns 2007). Wheat is the most widely cultivated cereal crop in the world and a staple food for many countries of the world. Consequently development of salt tolerant wheat will assist in feeding the increasing global population. The present study was conducted to evaluate the performance of newly developedD genome diverse wheat germplasms under saline conditions by measuring various physiological and biochemical traits. Evaluations were further made as to whether these biochemical and physiological traits could be utilized as selection criteria to screen wheat genotypes for salinity tolerance.

Material and Methods

Plant Material

Seeds of thirteen new synthetic hexaploid wheat genotypes (2n=6x=42; AABBDD) including two check varieties Kharchia-65 and Shorawaki were obtained from the Wheat Wide Crosses Program at National Agricultural Research Centre (NARC) Islamabad Pakistan (Table 1).

Growth Conditions and Treatment

The experiment was conducted under hydroponic conditions in the growth chamber of Plant Physiology Program of the Crop Sciences Institute National Agricultural Research Centre (NARC) Islamabad Pakistan. Wheat seeds were sown in jiffy pots and were allowed to grow for ten days after which the seedlings were transplanted into a hydroponic system containing 3.0 L of full strengthHoagland's solution (Hoagland and Arnon 1950). Thehydroponic system was artificially prepared and comprisedof black polyethylene boxes (3.0 dm3 3.5 L capacity). The growing conditions were a 12 h photo period of a minimumof 400-500 mol m-2 s-1 photosynthetically active radiation at 27oC. The temperature during the dark period was 25oC. The seedlings were allowed to grow in the hydroponics for3 days after which the seedlings (13 days old) were subjected to 0 75 and 150 mM NaCl levels as described below. On day 4 NaCl was added to the Hoagland's solution (in two split doses 50% added on day 4 followed by50% on day 5) with the quantity of NaCl was adjusted according the treatment dose. The plants were allowed to grow in the presence of the various treatments for 5 days under conditions described above. Twenty day old plants (after seeding) were harvested and data were collected immediately on shoot and root length. The plants were dried in an oven (65C) for at least 72h after which shoot and root dry weights were collected.

Determination of Physiological and Biochemical Parameters

Gas exchange measurements were taken using a portable photosynthesis system (LI-6400 Li-cor Inc. Lincoln NE) on the fully expanded 3rd leaf of each plant. Data on photosynthesis (A) transpiration rate (E) and stomatal conductance (gs) were determined. Measurements were taken between 14:00 and 16:00 h (Ben-Asher et al.2006).

At the end of the experiment the 3rd fresh leaf of each plant was harvested and immediately immersed in 15 mL80% ethanol in a Pyrex test tube capped and incubated for10 min in a water bath at 85oC. The tubes were subsequently cooled in a dark room. This crude extract was used for chlorophyll Na+ and K+ determination.For chlorophyll determination samples were taken from the crude extract and readings were taken at A666 immediately with care to minimize exposure to light using a spectrophotometer (Unico-UV 2100 Japan). Chlorophyll content was calculated according to Arnon (1949).For Na+ and K+ determination acetic acid was added to the crude extract to a final concentration of 100 M m-3and the tissue was re-extracted for 24 h at 4oC (Yeo andFlowers 1983). Sodium and potassium contents in the extract were then determined by atomic absorption spectrophotometer (Perkin-Elmer Model 4100L). The remaining leaf material was dried weighed and the concentration of chlorophyll Na+ and K+ were presented on a leaf dry weight basis.Sugar content of fresh leaves was measuredby the procedure of Dubois et al. (1956). Wheat fresh leaves were homogenized in 10 mL of distilled water using a clean pestle and mortar. The homogenate was centrifuged at 3000 rpm for 5 min followed by the addition of 1 mL of 80% (v/v) phenol. The extract was incubated for 1 h at room temperature followed by the addition of 5 mL concentrated H2SO4 and vigorously mixed. Readings were taken at A420 using a spectrophotometer. A glucose standard curve was prepared and the concentration of samples was determined using this standard curve.Proline content was analyzed by the method of Bateset al. (1973). Fresh leaves were homogenized in 10 mL of3% aqueous sulfosalicylic acid and filtered through Whatman 42 filter paper. The filtrate was mixed with 2 mL acid-ninhydrin and 2 mL of glacial acetic acid and placed in a water bath for 1 h at 100C. It was then extracted with 4 mL toluene and readings were taken at A520 using a spectrophotometer.The amount of total soluble proteins was estimated with a similar extract (phosphate buffer extraction) as used in SOD (K-Na-phosphate buffer; 60 mM pH 7.8). The homogenate was centrifuged at 1000 rpm for 15 min; 0.5 mL of the supernatant and 0.5 mL distilled water were added to 3 mL 5 fold diluted Bradford reagent (Bio-Red protein assay dye reagent). Absorbance was measured at595 nm. Protein content was calculated using a bovine serum albumin calibration curve and expressed on a fresh weight basis (Bradford 1976).The SOD activity was determined by measuring the ability of the enzyme to inhibit phytochemical reduction of tetrazolium blue according to the method of Giannopolitis and Ries (1977). Fresh leaf tissue (0.25 g) was homogenized

Table 1: Detail of genotypes studied comprising of two land races and thirteen synthetic hexaploid wheats

Genotypes###Pedigree/Germplasm detail

Kharchia-65###Land race from Rajasthan INDIA

Shorawaki###Land race from Baluchistan PAKISTAN

N-7###Triticum turgidum/Aegilops tauschii (N-7)

N-9###Triticum turgidum/Aegilops tauschii (N-9)

N-10###Triticum turgidum/Aegilops tauschii (N-10)

N-11###Triticum turgidum/Aegilops tauschii (N-11)

N-12###Triticum turgidum/Aegilops tauschii (N-12)

N-13###Triticum turgidum/Aegilops tauschii (N-13)

N-14###Triticum turgidum/Aegilops tauschii (N-14)

N-15###Triticum turgidum/Aegilops tauschii (N-15)

N-25###Triticum turgidum/Aegilops tauschii (N-25)

N-26###Triticum turgidum/Aegilops tauschii (N-26)

N-31###Triticum turgidum/Aegilops tauschii (N-31)

N-33###Triticum turgidum/Aegilops tauschii (N-33)

N-34###Triticum turgidum/Aegilops tauschii (N-34)

in an ice bath with 1 mL of 100 mM L-1 sodium phosphate buffer containing 1% polyvinyl pyrollidone (PVP). Then it was centrifuged at 10000g for 15 min at 4oC. For SOD the reaction mixture (3 mL) contained: K-Na- phosphate buffer (60 mM pH 7.8) methionine (13 mM L-1) riboflavin (12 mM L-1) P-tetrazoleum blue (80 M) EDTA (0.1 mM) and 100 L of enzyme extract. The reaction was run for 10 min under illumination with 15W fluorescence light. Reaction was stopped by switching off the light. The absorbance of the mixture was measured at A560 nm. The reaction mixture without the enzyme extract was utilized as control and a dark control mixture acted as a blank. One unit of SOD activity was taken as the quantity of enzyme that is able to inhibit tetrazoleum blue reduction by 50% as determined at A650 nm. SOD activity was expressed in arbitrary units per mg of fresh weight.Peroxidase activity (POD) was assayed by the method of Pundir et al. (1999). Fresh leaf tissue (0.25 g) was homogenized in an ice bath with 1 mL of 100 mM L-1 sodium phosphate buffer containing 1% PVP. Then it was centrifuged at 10000 g for 20 min at 4oC. POD; CAT enzyme extract was determined with this supernatant. The assay mixture contained 1.8 mL 50 mM L-1 sodium phosphate buffer 0.1 mL phenol 0.1 mL 4- aminophenazone and 0.1 mL enzyme extract was incubated at 40oC for 5 min. Subsequently H2O2 (1 mM L-1) was added after incubation and absorbance was recorded at 520 nm. The quantity of H2O2 consumed was calculated through a standard curve based on absorption A520 and H2O2. Enzyme activity (1 unit) was expressed as the quantity of H2O2 consumed per min per mg protein.Catalase (CAT) activity was determined using themethod of Aebi (1984). The supernatant was used for CAT determination. The reaction mixture included 50 mM L-1 sodium phosphate buffer 50 mM L-1 H2O2 and 50 mL of enzyme extract. The activity was determined by observing the decline in absorbance at 240 nm as a result of H2O2 consumption and expressed as quantity of H2O2 utilized per minute per mg of protein.

Statistical AnalysisThe experiment was organized as Completely RandomizedDesign. Data collected on variables were analyzed usingMinitab software (Minitab 15.0 Minitab Inc. State College PA USA). One-way ANOVA (analysis of variance) was used and Duncan's Multiple Range (DMR) test was performed to test differences among treatment means. Only differences statistically significantly different at P less than 0.05 are discussed in this report. In some cases mean values arepresented as mean value with standard errors (SE). Interactions between shoot dry weight and physiological or biochemical traits were analyzed by simple linear regression at 150 mM NaCl stress applying MS-Excel-2007 to determine the suitability of different physiological and biochemical traits as selection criteria for salt tolerance. In addition salt tolerance indices were calculated by dividing each observation at a given salinity by the average of the control. Ranking numbers were allocated to groups on the basis of means and were applied to score the genotypes.Group rankings were acquired on the basis of Ward'sminimum variance analysis of the averages of the salt tolerance indices for 4 plant biomass parameters (shoot length root length shoot dry weight and root dry weight) and 12 physiological and biochemical attributes (i.e. A E gs K+:Na+ ratio chlorophyll sugar proline soluble protein SOD POD and CAT). Group rankings were achieved from the average of means of the various parameters in each group. A sumMation was acquired by totaling the number of rankings at 150 mM NaCl in each genotype. Genotype rankings were finally determined on the basis of sumMations most tolerant genotypes with the smallest sums (Zeng et al. 2002).

Results

Plant Biomass

Our data showed that shoot dry weight root dry weight shoot length and root length were decreased with increasing level of salinity (Tables 2 3). Under low salt concentration (75 mM NaCl) the deleterious effects of salt stress were less pronounced than the higher salt concentration (150 mM NaCl). Reductions in shoot dry weight due to the application of 75 and 150 mM NaCl was 16 and 22% respectively for root dry weight was 15 and 20% shoot length was 10 and 16% and root length was 17 and 30% as compared to control plants (Table 2). The wheat genotypes Kharchia-65 Shorawaki N-7 N-9 and N-13 were least affected by increasing salinity. For example shoot dry weight at 150 mM NaCl were decreased by 12 13 16 17 and 18% and root dry weight at 150 mM NaCl declined by

Table 2: Effect of different levels of NaCl on the shoot and root dry weight of wheat genotypes

###Shoot dry weight (mg plant-1)###Root dry weight (mg plant-1)

Genotypes 0###75###150 Mean###0###75###150###Mean

###mM mM mM###mM mM mM

Kharchia- 37.6 36.0 33.0 36.0 a###25.1 24.1 21.1 23.2 a

65

Shorawaki 35.4 33.4 30.7 33.1ab###23.4###22.3###19.4###22.0 ab

N-7###36.2 34.1 30.3 34.0ab###22.1###21###20.3###21.1 abc

N-13###34.2 31.1 28.1 31.1a-d###20.3###18.7###18.2###19.0 a-d

N-9###35.2 32.2 28.8 32.1abc###21.3###19.7###19.2###20.0 abc

N-33###33.6 30.4 27.5 31.0a-e###20.1###18.2###17.4###19.0 a-d

N-12###25.0 21.3 18.6 21.6e-f###18.1###16.2###14.8###16.4 a-d

N-34###29.0 24.5 21.8 25.1b-f###16.2###14.1###13###15.0 a-d

N-26###27.0 22.0 19.0 23.0def###17.3###15###14.2###16.0 a-d

N-11###27.0 22.3 20.8 23.4c-f###16.5###14.5###13.2###15.0 a-d

N-31###22.0 18.0 16.5 19.0 f###16.2###13.6###12.5###14.1 bcd

N-10###26.0 20.0 18.0 21.3ef###15.6###12.8###11.6###13.3 bcd

N-15###27.0 21.0 20.0 23.0def###14.8###12.1###10.8###13.0 cd

N-25###25.0 19.0 17.0 20.3 f###13.1###10.7###9.4###11.0 d

N-14###23.0 18.0 16.0 19.0 f###12.5###10.1###8.5###10.4 d

Mean###32.0a 27.0b 25.0b###20.0a###17.0b###16.0b

Table 3: Effect of different levels of NaCl on the shoot and root length of wheat genotypes

###Shoot length (cm)###Root length (cm)

Genotypes###0###75###150 Mean 0###75###150###Mean

###mM###mM mM###mM mM mM

Kharchia-###33.2###32.1 31.5 32.30a 14.5 13.5 13.0 13.8 ab

65

Shorawaki###32.5###31###30.5###31.3abc###13.7###12.5###11.8###12.7abc

N-7###32.5###30.9###30.2###31.2abc###11.2###10.1###11.4###10.2 bc

N-13###31.41###29.7###28.9###30.0abc###14###12.7###11.2###12.6abc

N-9###33.2###31.2###30.1###31.5abc###14###12.6###11.3###12.6abc

N-33###29.6###27.6###26.6###27.9a-e###11.3###9.8###8.6###9.9 c

N-12###31.3###28.4###26.8###28.8a-d###16.3###13.8###11.2###13.8 ab

N-34###30.7###27.6###24.3###28.2a-e###11.7###9.7###9.11###10.2 bc

N-26###29.4###26.4###24.8###26.9b-f###11.3###9.56###8.2###9.7 c

N-11###30.3###27.1###25.3###27.6a-e###14.3###12###10.2###12.2abc

N-31###25.3###21.6###19.5###22.1 f###12###10###8.7###10.2 bc

N-10###31.5###26.7###24.6###27.6a-e###16###13###9.5###12.8abc

N-15###29.6###26.1###22.8###26.2c-f###15###12.3###9.8###12.4abc

N-25###27.7###22.8###20.7###23.7ef###13###11.5###9.0###11.2bc

N-14###28.5###24.2###21.1###24.6def###16.3###14.6###12.3###14.4a

Mean###30.5a###27.3b###25.0 c###14.6a###12.0b###10.3 c

6 7 8 9 and 10% for Kharchia-65 Shorawaki N-7 N-9 and N-13 respectively as compared to the control treatment (Table 2). Shoot dry weight for N-25 N-10 N-14 and N-26 were most sensitive declining 32 31 30 and 29% respectively at 150 mM NaCl stress. Similarly root dry weight showed maximum reduction in genotypes N-14 N-25 N-15 and N-10 decreasing 32 28 27 and 26% respectively at 150 mM NaCl. Of the 15 wheat genotypes nine showed more than 10% reduction in their shoot length whereas Kharchia-65 Shorawaki N-7 N-9 and N-13 performed better at both 75 and 150 mM NaCl (Table 3). Maximum reduction in shoot length was observed for N-14 N-25 and N-15 (less than 23%) and minimum for Kharchia-65 Shorawaki N-7 and N-13 (less than 8.0%). At 150 mM NaCl 10 genotypes demonstrated more than 20% reduction in root

Table 4: Effect of different levels of NaCl on K+:Na+ ratio chlorophyll and soluble sugar content of wheat genotypes

Genotypes###K+/Na+ (ratio)###Chlorophyll content (mg g-1 D. wt.)###Soluble sugar content (mg g-1 D. wt.)

###0 mM###75 mM###150 mM###0 mM###75 mM###150 mM###0 mM###75 mM###150 mM

Kharchia-65###5.80.8###4.20.32###1.90.19###22.81.5###19.51.0###13.80.60###211.6###30.02.4###41.54.0

Shorawaki###5.70.95###4.00.34###1.70.16###22.52.0###19.20.90###13.50.44###20.52.4###29.33.1###40.23.5

N-7###5.60.76###3.80.30###1.50.14###22.31.4###18.50.88###13.20.50###20.11.8###30.22.7###38.42.9

N-13###5.50.50###3.60.24###1.40.15###21.51.6###18.10.52###12.60.44###18.61.5###29.32.0###37.53.1

N-9###5.50.65###3.70.22###1.30.13###20.51.5###17.40.67###130.40###19.51.3###28.21.5###35.12.4

N-33###5.40.30###3.50.18###1.00.12###18.61.4###170.58###12.40.29###18.21.2###27.41.6###34.362.1

N-12###5.00.60###3.00.39###0.670.11###20.21.2###15.60.56###11.40.36###18.32.1###26.51.2###32.03.0

N-34###5.20.24###2.70.45###0.650.08###20.51.3###15.20.42###10.80.51###17.41.7###26.31.4###29.22.5

N-26###3.80.58###2.60.36###0.590.10###19.61.2###14.50.50###10.50.39###17.51.5###25.01.8###30.22.3

N-11###3.50.65###2.10.29###0.420.12###19.21.4###14.20.46###9.10.32###15.81.3###22.01.5###29.52.4

N-31###3.40.23###1.70.31###0.230.08###191.2###13.80.35###8.90.28###17.51.1###24.61.8###31.41.8

N-10###3.30.40###1.50.21###0.310.07###18.61.1###13.50.43###8.50.37###17.20.9###23.51.5###28.62.2

N-15###3.20.35###1.20.25###0.280.06###18.41.0###130.32###8.70.33###16.00.69###22.71.9###29.51.9

N-25###2.30.30###1.00.15###0.240.05###18.93###12.60.38###8.60.26###15.40.43###23.51.2###27.81.8

N-14###2.00.21###0.90.14###0.260.04###18.2.90###12.30.41###7.90.30###14.50.56###22.31.1###27.52.0

Mean###4.34 a###2.63 b###0.83 c###20.0 a###15.63 b###10.80 c###20.18 c###26.10 b###32.80 a

Table 5: Effect of different levels of NaCl on proline and soluble protein content of wheat genotypes

###Proline contet###Soluble protein content

###( g g-1 fresh wt)###(mg g-1)

Genotypes 0 mM 75mM 150mM 0 mM###75 mM###150 mM

Kharchia- 301.2 422.4 584.0 0.720.09 1.00.09 1.280.14

65

Shorawaki 291.5 403.1 553.5 0.670.04 0.940.1 1.250.16

N-7###301.4 382.7 562.9 0.680.06 0.890.08 1.20.12

N-13###271.2 362.0 523.1 0.640.05 0.760.07 0.950.10

N-9###271.1 402.6 502.4 0.580.3 0.880.08 0.90.09

N-33###281.0 353.0 472.1 0.490.42 0.70.06 0.820.06

N-12###201.6 300.8 453.0 0.520.06 0.660.04 0.890.08

N-34###181.3 281.3 422.5 0.620.05 0.820.03 0.90.06

N-26###161.2 261.8 402.3 0.430.02 0.620.04 0.860.07

N-11###12.92 201.0 302.4 0.560.06 0.720.03 0.880.05

N-31###100.8 161.0 291.8 0.40.05 0.550.04 0.720.06

N-10###90.9 150.8 282.2 0.380.02 0.550.024 0.670.05

N-15###100.7 141.0 251.9 0.490.02 0.680.04 0.750.04

N-25###120.8 150.9 271.8 0.370.04 0.520.03 0.480.03

N-14###131.0 161.0 232.0 0.420.03 0.560.03 0.680.05

Mean###19.4c 27.40b 37.0a###0.53 c###0.73 b###0.87 a

length while 5 genotypes showed less than 21%. The maximum decline in root length was observed for N-10 and the minimum for Kharchia-65 (Table 3). A positive correlation was found between shoot dry weight with root dry weigh (r2: 0.82 ) and shoot dry weight with shoot length (r2: 0.60 ). However correlation between shoot dry weight with root length was not significant (r2: 0.23 ns) (Table 8). Salt tolerance ranking based on plant biomass showed that wheat genotypes Kharchia-65 Shorawaki N-7 N-9 and N-13 were ranked as salt tolerant while genotypes N-12 and N-33 were grouped as moderately tolerant and the remainder of genotypes were grouped as sensitive (Table 9).

Physiological and Biochemical Attributes

Our data on K+:Na+ ratio and chlorophyll content indicated that both were reduced with increasing levels of salinity(Table 4). At 75 and 150 mM NaCl for example K+:Na+ratio was decreased by 39 and 80% respectively andchlorophyll content was decreased by21 and 45% respectively as compared to the control treatment (Table 4).The K+:Na+ ratio ranged from 0.9 to 4.2 at 75 mM NaCl and 0.26 to 1.9 at 150 mM NaCl; While chlorophyll contentranged from 12.3 to 19.5 (mg g-1) at 75 mM NaCl and 7.9to13.8 (mg g-1) at 150 mM NaCl. Minimum reduction in K+:Na+ ratio was recorded in genotypes Kharchia-65 Shorawaki N-7 N-9 and N-13 (28 29 32 34 and 32%) respectively at 75 mM NaCl and 67 68 73 74 and 76% at150 mM NaCl. Conversely maximum reduction in K+:Na+ratio was obtained with genotypes N-10 N-15 N-25 and N-14 which were 54 62 56 and 55% respectively at 75 mM NaCl and 90 91 89 and 87% at 150 mM NaCl. Maximum chlorophyll content was observed in the same genotypes (Kharchia-65 Shorawaki N-7 N-13 and N-9) at both 75 and 150 mM NaCl levels. Whereas minimum chlorophyll contents were recorded with N-10 N-15 N-25 and N-14 at150 mM NaCl (Table 4).Soluble sugar proline and soluble protein contents were increased at 75 and 150 mM NaCl (Tables 4 5). On average soluble sugar content increased over the control by29 and 62% respectively proline content by 41 and 90% and soluble protein content by 36 and 64% at 75 and 150 mM NaCl respectively. Among the evaluated genotypes soluble sugar content ranged from 22 to 30 (mg g-1 dry wt.) at low salinity and from 27.5 to 40.5 (mg g-1 dry wt.) at high salinity. Proline content ranged from 14 to 42 (g g-1 fresh wt.) at low salinity and 23 to 58 (g g-1 fresh wt.) for high salinity. Soluble protein content ranged from 0.52 to 1.0 (g g-1 fresh wt.) at low salinity and from 0.48 to 1.28 (mg g-1) at high salinity. Maximum sugar contents (41.5 40.2 38.437.5 and 35.1 mg g-1 dry wt.) were for genotypes Kharchia-65 Shorawaki N-7 N-9 and N-13 respectively at 150 mM NaCl; while minimum sugar accumulations (17.2 16.015.4 and 14.5 mg g-1 dry wt.) were for N-10 N-15 N-25

Table 6: Effect of different levels of NaCl on superoxide dismutase (SOD) peroxidase (POD) and catalase (CAT)

activities of wheat genotypes

###SOD (unit mg-1)###POD (unit mg-1)###CAT (unit mg-1)

Genotypes###0 mM###75 mM###150 mM###0 mM###75 mM###150 mM###0 mM###75 mM###150 mM

Kharchia-65###15.01.5###20.41.6###26.32.0###1283.6###1323.6###1454.6###402.5###482.6###542.8

Shorawaki###14.51.3###20.01.2###25.52.3###1253.8###1284.2###1425.0###372.2###462.7###533.1

N-7###14.01.1###22.02.2###28.41.8###1234.6###1262.8###1475.6###331.8###403.1###522.7

N-13###13.60.9###22.52.4###28.61.5###1256.0###1302.4###1504.9###323.5###383.6###483.7

N-9###13.51.3###21.41.5###26.41.9###1205.2###1252.5###1456.0###342.1###372.5###464.0

N-33###13.01.0###17.51.1###22.52.1###1247.3###1273.0###1455.4###321.8###363.7###442.5

N-12###12.60.4###16.51.5###22.02.0###1164.2###1252.8###1444.2###321.2###361.4###434.2

N-34###12.81.2###15.31.6###21.32.3###1213.9###1244.3###1413.2###341.6###381.8###423.2

N-26###12.60.8###17.51.4###19.01.6###1183.0###1235.6###1423.8###311.8###382.2###433.6

N-11###12.20.6###15.53.1###18.32.0###1192.9###1223.9###1383.2###301.1###351.9###413.3

N-31###11.50.8###14.61.6###18.01.5###1123.1###1214.0###1364.0###270.9###341.6###382.8

N-10###11.41.1###15.52.1###17.01.6###1203.4###1223.6###1303.4###261.1###301.4###403.0

N-15###10.61.0###14.61.5###16.51.8###1163.6###1233.4###1355.4###250.8###271.6###342.5

N-25###10.00.7###14.21.1###17.01.5###1102.7###1194.2###1334.6###200.7###261.8###292.1

N-14###9.50.67###12.31.4###15.81.4###1053.0###1185.0###1322.6###220.7###281.5###322.5

Mean###12.50c###17.30b###21.50a###118.50 c###124.3 bc###140.3 a###29.6 c###33.5 b###42.5 a

Table 7: Effect of different levels of NaCl on photosynthetic rate (A) transpiration rate (E) and stomatal conductance

(gs) of wheat genotypes

###A(u mol CO2 m-2 S-1)###E (m mol H2O m-2 S-1)###gs (u mol m-2 S-1)

Genotypes###0 mM###75 mM###150 mM###0 mM###75 mM###150 mM###0 mM###75 mM###150 mM

Kharchia-65###8.00.48###6.90.32###6.00.19###3.60.30###3.10.26###2.40.16###35416###29218###24318

Shorawaki###7.80.56###6.80.34###5.800.16###3.50.20###3.00.12###2.30.15###34220###28620###24016

N-7###7.90.50###6.20.30###5.800.14###3.20.14###2.30.18###1.550.14###35023###28517###23615

N-13###7.50.42###6.20.26###5.400.15###3.10.24###2.20.14###1.450.21###34621###28320###23812

N-9###7.60.47###6.10.22###5.500.13###30.16###2.30.20###1.390.29###33524###28017###23014

N-33###7.50.30###6.30.19###5.000.12###2.80.18###20.14###1.40.25###32622###27614###22516

N-12###7.00.20###5.40.39###4.800.11###2.50.14###2.10.24###1.20.20###31815###26215###22018

N-34###6.80.24###5.60.45###4.600.09###2.40.20###20.16###1.20.19###31618###25616###20620

N-26###6.50.52###5.00.36###4.200.10###2.50.26###1.80.18###1.10.24###31117###24517###20021

N-11###6.30.62###5.30.29###3.900.12###2.30.31###1.70.14###0.960.17###30523###25014###19515

N-31###6.40.23###4.60.31###3.700.08###2.40.16###1.80.20###0.920.10###30219###25116###19412

N-10###6.00.40###4.80.21###3.600.07###2.40.18###1.60.14###0.850.11###29516###23621###19016

N-15###5.80.35###4.40.25###3.100.06###2.60.14###10.19###0.520.15###29320###24518###18719

N-25###5.60.30###4.60.15###3.400.05###2.30.17###1.30.13###0.810.11###28026###23516###18014

N-14###5.50.21###4.50.14###3.200.04###2.20.10###1.50.23###0.840.12###28616###24015###18410

Mean###7.00 a###5.50 ab###4.51 c###2.72 a###1.99 a###1.25 b###317.3 a###261.5 b###211.2 c

and N-14 respectively in the absence of salt. Likewise higher proline contents (58 55 56 52 and 52 g g-1 fresh wt.) were found for the aforementioned genotypes and minimum proline contents (28 25 27 and 23 g g-1 fresh wt.) were for N-10 N-15 N-25 and N-14 respectively in absence of salt (Table 5). Higher soluble protein contents were found in Kharchia-65 Shorawaki N-7 N-9 N-34 and N-11 at 150 mM NaCl stress. Minimum soluble protein contents were recorded for N-10 and N-25.Activities of the enzymes superoxide dismutase (SOD) and catalase (CAT) were increased with 75 and 150 mM NaCl. However POD increased at 150 mM NaCl; there were no significant increases in POD due to treatment with75 mM NaCl (Table 6). SOD activity ranged from 13.3 to24.5 (units mg-1) at low salinity and 15.8 to 28.6 (units mg-1) at high salinity; while POD activity ranged from 118 to 132 (units mg-1) at low salinity and 130 to 150 (units mg-1) athigh salinity. Similarly CAT activity ranged from 26 to 48 (units mg-1) at low salinity and 29 to 54 (units mg-1) at high salinity. Our results also indicated that SOD POD and CAT activities increased 38 4.5 and 13% with the application of75 mM NaCl and 72 19 and 43% respectively at 150 mM NaCl. At 150 mM NaCl wheat genotypes Kharchia-65Shorawaki N-7 N-9 and N-13 had higher SOD activity levels (26.3 25.5 28.4 and 26.4 units mg-1) and CAT (5453 52 48 and 46 units mg-1); while maximum PODactivities (150 147 145 144 and 145 units mg-1) were for genotypes N-13 N-7 Kharchia N-9 and N-33 respectivelyat 150 mM NaCl.Gas exchange attributes such as leaf photosynthetic rate (A) transpiration rate (E) and stomatal conductance (gs) were reduced with the application of 150 mM NaCl in all the wheat genotypes. At 150 mM NaCl minimum reductions in photosynthetic rate were for Kharchia-65

Table 8: Equation of linear regression between the values of shoot dry weight and physiological and biochemical attributes in wheat at 150 mM NaCl

Physiological/biochemical###Regression equation###r2

attributes

Root dry weight###y = 0.542X + 0.001###0.82

Shoot length###y = 534.3 X + 14.25###0.60

Root length###y = 116.7X + 7.593###0.23 ns

+###+

K /Na ratio###y = 51.93X - 0.579###0.92

Chlorophyll###y = 327.9 X + 3.32###0.87

Soluble sugar###y = 849X + 18.19###0.78

Proline###y = 2134X 2.586###0.85

Soluble protein###y = 34.19X + 0.075###0.74

SOD###y = 985.0X + 0.337###0.90

POD###y = 774.7X + 122.3###0.58

CAT###y = 0.776X + 0.024###0.89

A###y = 153.5X + 0.969###0.83

E###y = 74.96X 0.490###0.70

gs###y = 3522X + 129.9###0.85

Table 9: Ranking for relative salt tolerance of 15 wheat genotypes in terms of plant dry biomass at 150 mM NaCl

Genotypes###SDW###RDW###SL###RL###Sum###Ranking

Kharchia-65###1###1###1###1###4###Tolerant

Shorawaki###1###1###1###2###5###Tolerant

N-7###1###1###1###2###5###Tolerant

N-13###1###1###1###2###5###Tolerant

N-9###1###1###1###2###5###Tolerant

N-33###1###2###2###4###9###Moderate

N-12###3###2###2###2###9###Moderate

N-34###2###3###3###3###11###Sensitive

N-26###3###2###3###4###12###Sensitive

N-11###2###2###3###3###10###Sensitive

N-10###3###3###3###3###12###Sensitive

N-31###4###3###4###4###15###Sensitive

N-15###2###3###4###3###12###Sensitive

N-25###4###4###4###3###15###Sensitive

N-14###4###4###4###1###13###Sensitive

Shorawaki N-7 N-13 and N-9 transpiration rate in Kharchia-65 and Shorawaki and stomatal conductance for genotypes Shorawaki N-12 N-33 N-9 and Kharchia-65. There were strong correlations between shoot dry biomass and K+/Na+ ratio chlorophyll proline SOD CAT and gs (r2: 0.92 0.87 0.85 0.90 0.89 0.85 respectively); hence these could be used as selection criteria (Table 8). Different physiological and biochemical attributes for the suitability of selection criteria for salt tolerance in synthetic wheats was also evaluated by determining relationships between physiological attributes and shoot dry biomass using linear regression analysis (Table 9). Salt tolerance ranking on the basis of physiological and biochemical attributes indicated that genotypes Kharchia-65 Shorawaki N-7 N-9 and N-13 could be grouped as salt tolerant; genotypes N-33 and N-12 as moderately tolerant and genotypes N-10 N-15 N-25 and N-14 as sensitive (Table 10).

Discussion

Our results clearly indicate that increasing level of NaCl had adverse effects on wheat plant dry biomass production. However there was variability in salt tolerance among the tested wheat genotypes. Salt sensitive genotypes had greater decrease in plant dry biomass than salt tolerant genotypes. The variation in response of the tested genotypes could be largely related to plant genetics. It has been reported that wheat genotypes having greater plant biomass at the seedling stage show better salt tolerance at maturity (Ahmadi and Ardekani 2006). Establishment of more vigorous seedlings is an important step in the crop life cycle. Evaluation of genotypes for salinity tolerance at the seedling stage can save significant time.

The decrease in plant dry biomass plant height and root length under saline conditions was associated with higher K+:Na+ ratios and better photosynthesis. In the current study wheat genotypes Kharchia-65 Shorawaki N-7 N-9 and N13 maintained higher plant biomass and showed minimum growth reduction when exposed to 75 and 150 mM NaCl (Tables 2weight and root dry weight at 150 mM NaCl. This is not surprising as plants with healthy and long roots are able to absorb more water and especially for plants under stress; this may result in higher photosynthetic levels and consequently increased shoot biomass. Under environmentally controlled conditions genotype salinity tolerance is most clearly indicated by dry plant biomass accumulation (Meneguzzo et al. 2000). In wheat decreased shoot biomass was attributed to the reduction in water potential and growth associated with osmotic effects under salinity stress (Munns et al. 1995).

Salinity tolerance by plants includes the ability of plant to exclude Na+ and the capacity to accumulate Na+ in leaf tissue. Our data indicates that the K+:Na+ ratio declines with increasing salt concentration for all genotypes. In this regard various wheat genotypes were differentially affected by salt stress due to their different genetic compositions. Salt tolerant genotypes Kharchia-65 Shorawaki N-7 N-9 and N-13 maintained higher K+:Na+ ratios at all the salinity levels (Table 4). Selection for physiological mechanisms of salt tolerance such as selection for germplasm with low Na+ uptake or with high selectivity for K+ over Na+ have successfully contributed in salt tolerance (Flowers 2004). There was a strong correlation between shoot dry biomass and K+:Na+ ratio (Table 8).

Salinity tolerance in glycophytes such as wheat is well known to be associated with Na+ exclusion and wheat genotypes with a low capacity in this regard were categorized as salt sensitive genotypes (Din et al. 2008; Gurmani et al. 2013). The level of photosynthetic pigments such as chlorophyll content plays a vital role in photosynthesis. In the present investigation increased concentrations of NaCl reduced chlorophyll contents in all the wheat genotypes. The current

Table 10: Ranking for relative salt tolerance of 15 wheat genotypes in terms of physiological and biochemical attributes at

150 mM NaCl

Genotypes###K/Na###Chlorophyll###Sugar###Proline###Protein###SOD###POD###CAT###A###E###gs###Sum###Ranking

Kharchia-65###1###1###1###1###1###1###2###1###1###1###1###12###Tolerant

Shorawaki###1###1###1###1###1###1###2###1###1###1###1###12###Tolerant

N-7###1###1###1###1###1###1###2###1###1###2###1###13###Tolerant

N-13###1###1###1###1###2###1###1###1###1###2###1###13###Tolerant

N-9###1###1###1###1###1###1###2###1###1###2###1###13###Tolerant

N-33###2###2###2###2###3###2###2###2###2###2###2###23###Moderate

N-12###2###2###2###2###2###2###2###2###2###3###2###23###Moderate

N-34###2###2###2###2###2###3###3###2###3###3###3###27###Sensitive

N-26###3###3###3###3###3###3###3###2###3###3###3###32###Sensitive

N-11###3###3###4###4###3###3###3###2###3###4###4###36###Sensitive

N-31###4###3###4###4###4###4###4###3###4###4###4###42###Sensitive

N-10###4###4###4###4###4###4###4###3###4###4###4###43###Sensitive

N-15###4###4###4###4###4###4###4###3###4###4###4###43###Sensitive

N-25###4###4###4###4###4###4###4###4###4###4###4###44###Sensitive

N-14###4###4###4###4###4###4###4###4###4###4###4###44###Sensitive

work showed that tolerant genotypes Kharchia-65 Shorawaki N-7 N-9 and N-13 showed higher level of chlorophyll than moderate and sensitive genotypes at all the salinity levels; this is comparable with earlier findings in a range of crops e.g. cotton (Shaheen et al. 2012) wheat(Gurmani et al. 2013) and maize (Kaya et al. 2013). Apositive correlation (r2 = 0.92) was observed between chlorophyll content and shoot dry biomass at 150 mM NaCl suggesting that reductions in shoot dry biomassmay have been partly due to decreases in chlorophyllcontent.Another important tolerance mechanism exhibited byplants under stress conditions is the accumulation of compatible solutes such as sugar carbohydrates and proline (Munns and James 2003; Kaya et al. 2013; Gurmani et al.2013). Genotypes having higher K+:Na+ ratios and chlorophyll contents under saline conditions were better able to make osmotic adjustments by increasing osmoprotectants such as proline soluble sugar and soluble protein contents. Thus the salt tolerance potential of tolerant genotypes (Kharchia-65 Shorawaki N-7 N-9and N-13) is associated with elevated level of osmolytes inleaf tissues. Increased production of compatible solutes under salt stress has already been reported in wheat (Din et al. 2008) maize (Kaya et al. 2013) Chenopodium quinoa willd. (Prado et al. 2000) and tomato (Amini and Ehsanpour 2005). Afzal et al. (2006) reported that increases in leaf soluble protein contents of wheat plants occur regardless of their sensitivity to salt stress; however the level of increase or decrease in soluble protein under saline conditions is genotype dependent (Amini and Ehsanpour 2005). In the present investigations tolerant genotypes (Kharchia-65 Shorawaki N-7 N-9 and N-13) accumulated higher levels of soluble protein under saline conditions (Table 4).Salinity induced inhibition of plant growth is associated with damage caused by ROS. These ROS are free radicals in atoms or group of atoms containingminimum one unpaired electron (Polle 2001). It is well known that salinity stress activate oxidative stress within the plant system generally known as oxidative burst (Foyer and Noctor 2003). Superoxide dismutase (SOD) plays an important role in ROS detoxification by catalyzing the conversion of free O2 to O2 and H2O2; SOD activity is correlated with stress conditions (Davies and Dow 1997). A strong relationship between efficient antioxidant system and plant salinity tolerance has been reported by Kaya et al. (2013) thus antioxidative enzyme levels could be a good indicator of plant performance under salt stress. In the present study SOD activities in the evaluated wheat genotypes were increased with the increasing level of salinity stress and were greater in tolerant genotypes (Kharchia-65 Shorawaki N-7 N-9 and N-13) than sensitive genotypes (Table 6). An increase in SOD activity in the leaves of salt stressed maize plants has been reported (Kaya et al. 2013).

Peroxidases (POD) play a role in scavenging hydrogen peroxide generated in chloroplasts as well as in plant growth processes and oxidation of toxic compounds (Dionisio-Sese and Tobita 1998). Salinity stress enhances POD activity levels and higher POD activities have been reported in sensitive rice cultivars than tolerant ones (Mittal and Dubey 1991). In the current investigations accumulation of POD activity was uneven among the tested wheat genotypes; however N-13 had the highest level of POD activity at 150 mM NaCl (Table 4).

Catalase (CAT) plays a vital role in plant defense against oxidative stress and can catalyse a redox reaction by dismutation of H2O2 to oxygen and water. Kaya et al. (2013) reported that induction of salt stress is linked with enhanced CAT activity in leaves of maize plants. We also found an increase in CAT activity when NaCl levels increased and higher CAT levels in tolerant genotypes (Kharchia-65 Shorawaki N-7 N-9 and N-13) than sensitive genotypes (Table 6). Overall a range of SOD POD and CAT responses have been reported to occur under saline conditions and across a range of crops indicating that different crops and different levels of tolerance within the same crop could result in diverse kinds of antioxidant responses related to scavenging of ROS which could be due by genetic diversity.Electron transport is a key part of photosynthesis and determination of photosynthetic levels is one of the basic criteria for the evaluation of stress tolerance in various crop species (Ashraf 2004). Reductions in photosynthetic rate (A) transpiration rate (E) and stomatal conductance due to salinity stress have been reported in crops such as cotton (Shaheen et al. 2012) wheat (Gurmani et al. 2013) and olive (Abusafieh et al. 2011). The present work showed that photosynthetic rate (A) transpiration rate (E) and stomatal conductance (gs) of all the genotypes diminished at higher salinity (150 mM NaCl). However tolerant genotypes e.g. Kharchia-65 Shorawaki N-7 N-13 and N-9 were least affected by salinity (Table 7). Salt induce inhibition variables related to leaf gas exchange by cotton has been reported by Shaheen et al. (2012) who indicated that stomatal conductance and transpiration rate are the main determinants of growth and photosynthetic rate. In the present study a positive correlation was observed between shoot dry biomass and A E and gs (r2 = 0.83 0.70 and 0.85 respectively) suggesting that salt induced reductions in shoot dry biomass are at least partly because of changes in photosystem activity. In the reported work differences in salt induced reduction in plant biomass among wheat genotypes was potentially due to a disparity in genetic behavior with regard to gas exchange attributes.Based on our physiological and biochemical data on15 genotypes in growth chamber condition we conclude that K+:Na+ ratio photosynthetic capacity proline level and SOD activity were at higher levels in salt tolerant genotypes than in moderately tolerant and sensitive genotypes. Based on these traits we grouped the tested genotypes as tolerant moderately tolerant and sensitive. Based on these traits we grouped the tested genotypes as tolerant (Kharchia-65 Shorawaki N-7 N-9 and N-13) moderately tolerant (N-33 and N-12) and sensitive (all the remaining genotypes) towards salinity. These promising findings argue for further work regarding the salinity tolerance of selected genotypes under saline field conditions.

Acknowledgements

The authors gratefully acknowledge financial support from the Higher Education Commission (HEC) of Pakistan through Grant No. 2-6 (11) PDFP.

References

Abusafieh D. and G.D. Nanos 2011. Influence of ambient ozone pollution on olive leaf gas exchange irrigated with saline water. Int. J. Agric. Biol. 13: 806810Aebi H. 1984. Catalase in vitro. Method Enzymol. 105: 121126Afzal I. S.M.A. Basra M. Farooq and A. Nawaz 2006. Alleviation ofsalinity stress in spring wheat by hormonal priming with ABA salicylic acid and ascorbic acid. Int. J. Agric. Biol. 8: 2328Ahmadi S.H. and J.N. Ardekani 2006. The effect of water salinity ongrowth and physiological stages of eight canola (Brassica napus)cultivars. Irrig. Sci. 25: 1120.Amini F. and A.A. Ehsanpour 2005. Soluble protein prolinecarbohydrates and Na+/K+ changes in two tomato (Lycopersicon esculentum Mill.) cultivars under in vitro salt stress. Amer. J.Biochem. Biotechnol. 1: 212216Arnon D.I. 1949. Copper enzymes in isolated chloroplasts.Polyphenoloxidase in Beta vulgaris. J. Plant Physiol. 24: 115Ashraf M. and P.J.C Harris 2013. Photosynthesis under stressfulenvironments: An overview. Photosynthetica 51: 163190Ashraf M. 2004. Some important physiological selection criteria for salttolerance in plants. Flora 199: 361376Bates L.S. R.P. Waldren and L.D. Teare 1973. Rapid determination offree proline for water stress studies. Plant Soil 39: 205207Ben-Asher J. I. Tsuyuki B. Bravdo M. Sagih 2006. Irrigation ofgrapevines with saline water: I. leaf area index stomatal conductance transpiration and photosynthesis. Agric. Water Manage. 83: 1321Bradford M.M. 1976. A rapid and sensitive method for the quantitation ofmicrogram quantities of protein utilizing the principle of proteindye binding. Anal. Biochem. 72: 248254Davies H.A. and J.M. Dow 1997. Induction of extracellular matrixglycoproteins in brassica petioles by wounding and in response toXanthomonas campestris. Mol. Plant Microb. Interact. 10: 812820Din J. S.U. Khan and I. Ali 2008. Physiological responses of wheat (Triticum aestivum L.) varieties as influenced by salinity stress. J. Anim. Plant Sci. 18: 125129Dionisio-Sese M.L. and S. Tobita 1998. Antioxidant responses of riceseedlings to salinity stress. Plant Sci. 135: 19DuBois M. K.A. Gilles J.K. Hamilton P.A. Rebers and F. Smith 1956.Colorimetric method for determination of sugars and related substances. Anal. Chem. 28: 350356Farooq M. H. Bramley J.A. Palta and K.H.M. Siddique 2011. Heatstress in wheat during reproductive and grain filling phases. Crit. Rev. Plant Sci. 30: 491507.Farooq M. M. Hussain and K.H.M. Siddique 2014. Drought stress inwheat during flowering and grain-filling periods. Crit. Rev. PlantSci. doi:10.1080/07352689.2014.875291Farooq M. M. Irfan T. Aziz I. Ahmad and S.A. Cheema 2013. Seed priming with ascorbic acid improves drought resistance of wheat. J. Agron. Crop Sci. 199: 12-22.Farshadfar E. S.A. Safavi and M. AghaeeSarbarzeh 2008. Locating QTLs controlling salt tolerance in barley using wheatbarley disomic addition lines. Asian J. Plant Sci. 7: 149155Flowers T.J. 2004. Improving crop salt tolerance. J. Exp. Bot. 55: 307319Foyer C.H. and G. Noctor 2003. Redox sensing and signaling associated with reactive oxygen in chloroplasts peroxisomes and mitochondria. Physiol. Plant. 119: 355364Foyer C.H. M. Lelandais and K.J. Kunert 1994. Photooxidative stress inplants. Physiol. Plant. 92: 696717Giannopolitis C.N. and S.K. Ries 1977. Superoxide dismutases: 1.Occurance in higher plants. Plant Physiol. 59: 309314Gurmani A.R. A. Bano N. Ullah J. Zhang S.U. Khan and T.J. Flowers2013. Exogenously applied silicate and abscisic acid ameliorates the growth of salinity stressed wheat (Triticum aestivum L) seedlings through Na+ exclusion. Aust. J. Crop Sci. 7: 11231130Hoagland D.R. and D. Arnon 1950. The water culture method forgrowing plants without soil. Circular 347 California Agricultural Experiment Station University of CaliforniaBerkeley Berkeley.Ca USAHussain M. H.-W. Park M. Farooq K. Jabran and D.-J. Lee 2013.Morphological and physiological basis of salt resistance in different rice genotypes. Int. J. Agric. Biol. 15: 113118Jafar M.Z. M. Farooq M.A. Cheema I. Afzal S.M.A. Basra M.A. WahidT. Aziz and M. Shahid 2012. Improving the performance of wheat by seed priming under saline conditions. J. Agron. Crop Sci. 198:3845.Kaya C. M. Ashraf M. Dikilitas and A. L Tuna 2013. Alleviation of saltstressinduced adverse effects on maize plants by exogenous application of indoleacetic acid (IAA) and inorganic nutrients A field trial. Aust. J. Crop Sci. 7: 249254Meneguzzo S. F. NavariIzzo and R. Izzo 2000. NaCl effects on waterrelations and accumulation of mineral nutrients in shoots roots andcell sap of wheat seedlings. J. Plant Physiol. 156: 711716Mittal R. and R.S. Dubey 1991. Behaviour of peroxidases in rice: changesin enzyme activity and isoforms in relation to salt tolerance. PlantPhysiol. Biochem. 29: 3140Mujeeb-Kazi A. V. Rosas and S. Roldan 1996. Conservation of thegenetic variation of Triticum tauschii (Coss.) Schmal. (Aegilops squarrosa auct. non L.) in synthetic hexaploid wheats (T. turgidum L. s. lat. A- T. tauschii; 2n=6x=42 AABBDD) and its potential utilization for wheat improvement. Gen. Res. Crop Evol. 43: 129134Munns R. and R.A. James 2003. Screening methods for salinity tolerance: A case study with tetraploid wheat. Plant Soil 253: 201218Munns R. 2007. Utilizing genetic resources to enhance productivity ofsaltprone land. CAB Rev.: Perspectives in Agric. Vet. Sci. Nutr.Nat. Res. 2. No. 009Munns R. D.P. Schachtman and A.G. Condon 1995. The significance of a twophase growth response to salinity in wheat and barley. Aust. J. Plant Physiol. 22 561569Polle A. 2001. Dissecting the superoxide dismutaseascorbate glutathionepathway in chloroplasts by metabolic modeling. Computer simulations as a step towards flux analysis. Plant Physiol.126: 445462Prado F.E. C. Boero M. Gallardo and J.A. Gonzalez 2000. Effect of NaClon germination growth and soluble sugar content in Chenopodium quinoa willd seeds. Bot. Bull. Acad. Sin. 41: 2734Pundir C.S. V. Malik A.K. Bhargava M. Thakur V. Kalia S. Singh andN.K. Kuchhal 1999. Studies on horseradish peroxidase imMobilized onto arylamine and alkylamine glass. J. Plant Biochem. Biotechnol.8: 123126SamMons D.J. D.B. Peters and T. Hymowitz 1978. Screening soybeansfor drought resistance. I. Growth chamber procedure. Crop Sci. 18:10501055Shaheen H.L. M. Shahbaz I. Ullah and M.Z. Iqbal 2012. Morphophysiological responses of cotton (Gossypium hirsutum L.) to saltstress. Int. J. Agric. Biol. 14: 980984Trethowan R.M and A. Mujeeb-Kazi 2008. Novel germplasm resourcesfor improving environmental stress tolerance of hexaploid wheat.Crop Sci. 48: 12551265Wakeel A. M. Farooq M. Qadir and S. Schubert 2011. PotassiumSubstitution by Sodium in Plants. Crit. Rev. Plant Sci. 30: 401413Yeo A.R. and T.J. Flowers 1983. Varietal differences in the toxicity ofsodium ions in rice leaves. Physiol. Plant. 59: 189195Zeng L. M.C. Shannon and C.M.Grieve 2002. Evaluation of salt tolerancein rice genotypes by multiple agronomic parameters. Euphytica 127:235 245Zhang J. T.J. Flowers and S. Wang 2010. Mechanisms of sodium uptakeby roots of higher plants. Plant Soil 326: 4560
COPYRIGHT 2014 Asianet-Pakistan
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2014 Gale, Cengage Learning. All rights reserved.

 
Article Details
Printer friendly Cite/link Email Feedback
Publication:International Journal of Agriculture and Biology
Article Type:Report
Date:Aug 31, 2014
Words:9292
Previous Article:Expression cloning and characterization of ACC synthase and ACC oxidase genes in Paeonia lactiflora.
Next Article:Membrane-Active Antibacterial Compounds in Methanolic Extracts of Jatropha curcas and their Mode of Action against Staphylococcus aureus S1434 and...
Topics:

Terms of use | Privacy policy | Copyright © 2018 Farlex, Inc. | Feedback | For webmasters