Impaginato 553 Adv. Hort. Sci., 2019 33(4): 553­565 DOI: 10.13128/ahsc­8191 Evaluating the salt tolerance of seven fig cultivars (Ficus carica L.) A. Salimpour 1, M. Shamili 1 (*), A. Dadkhodaie 2, H. Zare 3, M. Hadadinejad 4 1 Horticultural Department, University of Hormozgan, Iran. 2 Department of Crop Production and Plant Breeding, School of Agriculture, Shiraz University, Shiraz, Iran. 3 Fig Research Station, AREEO, Estahban, Iran. 4 Horticultural Science, Research Institute of Biotic Technologies of Medicinal and Aromatic Plants, Sari Agricultural Sciences and Natural Resources University (SANRU), Iran. Key words: abiotic stress, electrolyte leakage, specific leaf area, stem diameter, stem length, stomata conductance, transpiration rate. Abstract: The growing demand for both fresh and dry figs worldwide is due to its richness in mineral compounds (i.e. iron and copper) and polyphenols. Considering the position of Iranian cultivars in global fig market, the present study examined the growth and photosynthetic rate of commercial fig cultivars (i.e. ‘Sabzʼ, ‘Siyahʼ, ‘Shah Anjirʼ, ‘Atabakiʼ, ‘Kashkiʼ, ‘Matiʼ and ‘Bar Anjirʼ) exposed to six salt treatments corresponding to the following electrical conduc­ tivities (EC): 0.5, 2, 4, 6, 8 and 10 dS m­1. The results indicated a decrease trend of stem length, stem diameter and leaf number in salt­exposed plants. The electrolyte leakage and protein content in all cultivars followed an ascending trend. The specific leaf area, relative water content, photosynthetic indices and nitrogen content followed a decreasing trend according with increasing salinity. The ‘Siyahʼ and ‘Sabzʼ, as the most salt­tolerant cultivars, had the maximum leaf abscission, the lowest transpiration rate and leaf water content under salt condition, compared to all other tested cultivars. Moreover, they had the most leaf succulence and leaf dry matter content and the lowest specific leaf area, which related to the balance between growth ratio and osmotic regulation under salt conditions. The ‘Shah Anjirʼ, as the most salt­sensitive cultivar, could not balance transpiration rate and leaf water content under salt treatment higher than 4 dS m­1. 1. Introduction The fig (Ficus carica L., 2n= 26) of the Moraceae family, is one of the first plants cultivated and consumed by human beings (Duenas et al., 2008). According to the FAO, the fig is harvested from 36,535 hectares of cultivated land, with an annual production of over one million tons (FAO, 2017). Iran is the third largest producer of dried figs in the world, as well as the fifth largest fresh fig producer in the world with a cultivated area of 53,101 hectares and a production of 70,730 tons per year of fresh figs (FAO, 2017). (*) Corresponding author: shamili@ut.ac.ir Citation: SALIMPOUR A., SHAMILI M., DADKHODAI A., ZARE H., HADADINEJAD M., 2019 ­ Evaluating the salt tolerance of seven fig cultivars (Ficus carica L.). ­ Adv. Hort. Sci., 33(4): 553­565. Copyright: © 2019 Salimpour A., Shamili M., Dadkhodai A., Zare H., Hadadinejad M. This is an open access, peer reviewed article published by Firenze University Press (http://www.fupress.net/index.php/ahs/) and distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Competing Interests: The authors declare no competing interests. Received for publication 19 June 2019 Accepted for publication 5 September 2019 AHS Advances in Horticultural Science http://creativecommons.org/licenses/by/4.0/ http://creativecommons.org/licenses/by/4.0/ http://creativecommons.org/licenses/by/4.0/ Adv. Hort. Sci., 2019 33(4): 553­565 554 T h e g r o w i n g d e m a n d f o r t h e fi g w o r l d w i d e (Aksoy, 2005) is due to its richness in mineral com­ pounds (i.e. iron and copper) and considerable amounts of vitamins A and C (Flaishman et al., 2008). The fig is consumed in fresh, dried, powdered, canned, chocolate­covered forms, and utilized in the preparation of jam, syrup and Muscat­Halvah (De Masi et al., 2005). Significant genetic variation in the fig species, due to obligatory outcrossing, has led to the establish­ ment of new genotypes with desirable properties. According to the latest reports, there are currently more than 600 known fruit­producing cultivars and genotypes, which are distinct in leaf morphology, growth vigor, internal and external color of the fruit, taste and quality index of the fruit, shape and thick­ ness of the fruit, the diameter of the ostiole, and pro­ ductivity period (Condit, 1955; Toribio and Montes, 1996; García­Ruiz et al., 2013). Sabz or Verde (green), Siyah (black), Shah Anjir (king fig), Atabaki, Kashki and Mati are considered as the most important and marketable cultivars of Iranian figs for local markets or export. The ‘Bar Anjirʼ is the most commonly­used caprifig (Condit, 1955; Pourghayoumi et al., 2016). Several research centers have focused on differ­ ent aspects of physiology and breeding of fig cultivars and genotypes. For example, some researchers emphasized on genetic diversity of fig using morpho­ logical (Khadivi et al., 2018) and molecular (Cabrita et al., 2001; Khadari et al., 2005; Giraldo et al., 2008) markers. Some others attempted to study the capri­ figs (Dalkılıç et al., 2011), while others have consid­ ered the variety of the fruit and its qualitative fea­ tures (Solomon et al., 2006; Polat and Caliskan, 2008; Ercisli et al., 2012). In addition, the variation in the behavior of fig cul­ tivars and genotypes to abiotic stress such as chilling (Karami et al., 2018), drought (Gholami et al., 2012) and salinity (Zarei et al., 2016) have attracted the researchers’ attention. Salinity is one of the most important environmen­ tal factors which reduces the growth, development and production of plants (Sevengor et al., 2011). While some researchers suggested reducing leaf area as the plants’ responses to the salinity stress, others enumerate reduced stem length, root length, fresh and dry weights, and relative leaf water content (Yamasaki and Dillenburg, 1999; Bolat et al., 2006; Najafian et al., 2008; Adish et al., 2010; Khayyat et al., 2014; Khoshbahkt et al., 2014; Soliman and Abd Alhady, 2017). Other important processes that are negatively affected by salinity are protein synthesis (Taylor et al., 2004; Murcute et al., 2010) and nitro­ gen metabolism (Owais, 2015; Ashraf et al., 2017), whereas in other studies the inhibition of plant growth caused by salinity has been attributed to a decrease in photosynthesis (Garcia­Sanchez et al., 2006). Fig is a moderate salt­tolerant crop (Golombek and Lüdders, 1990). The available studies on the response of fig commercial cultivars to different lev­ els of salinity indicated a significant variation in mor­ phological characteristics, growth parameters, physi­ ological behavior, photosynthetic efficiency, gas exchange ratio, product quality, and productivity (Essam et al., 2013; Metwali et al., 2014; Alswalmeh et al., 2015; Zarei et al., 2016, 2017; Soliman and Abd Alhady, 2017). Considering the position of Iranian cultivars in global fig market, the present study examined the growth and photosynthetic rate of commercial fig cultivars (i.e. ‘Sabzʼ, ‘Siyahʼ, ‘Shah Anjirʼ, ‘Atabakiʼ, ‘Kashkiʼ, ‘Matiʼ and ‘Bar Anjirʼ) exposed to six salt treatments corresponding to the following electrical conductivities (EC): 0.5, 2, 4, 6, 8 and 10 dSm­1 to identify the most salt­tolerant cultivar. 2. Materials and Methods The present study was conducted in the plant b r e e d i n g d e p a r t m e n t , F a c u l t y o f A g r i c u l t u r e , University of Shiraz (36° 29’ N and 32° 52’ E), Iran during 2016­2018. Plant materials The plant materials were included six 20­years­old edible fig cultivars (Sabz, Siyah, Shah Anjir, Atabaki, Kashki, Mati), and a caprifig (‘Bar Anjirʼ) were located at Estahban fig Research Station (36° 29’ N and 32° 52’ E) (Table 1). The hard­wood cuttings, 20 cm in length and one cm in diameter, were collected from one­year­old branches on March 25, 2016. The cut­ tings were treated with a fungicide (Benomyl 2000 ppm) and a rooting hormone (IBA solution 3000 ppm). Then, the upper side of the cutting was cov­ ered to prevent the decay, and each cutting was placed in a dark plastic bag (25 x 18 cm2), which was filled by sand. In the next stage, the bags were locat­ ed in the shade­house conditions (Temperature: 28±2°C D/18±2°C N, RH=50%, and 50% shade) and were irrigated twice a day. In June 2017, rooted­cut­ tings were transplanted in pots filled with 500 g of gravel and 20 kg of the media described in Table 2. Salimpour et al. ‐ Evaluating the salt tolerance of seven fig cultivars 555 The media included the mixture of soil, leaf compost and sand (1:1:1), which was steam­disinfected. A pressure plate extractor (Model ADC, by Santa Barbara, United States) was used to measure the media water capacity. The pots were kept under s h a d e ­ h o u s e c o n d i ti o n ( T e m p e r a t u r e : 3 0 ± 1 ° C D/18±0.5°C N, RH=50%, and 50% shade). Salt treatment The salt treatments were provided through the irrigation water. Treatments included low salt treat­ ments (EC= 0.5 and 2 dS m­1, A and B, respectively), intermediate salt treatments (EC= 4 and 5 dS m­1, C and D, respectively) and high salt treatments (EC= 8 and 10 dS m­1, E and F, respectively). In order to avoid osmotic stress, salt treatments were introduced gradually, starting from 1/4 up to the final concentration. Then, irrigation frequency was calculated based on the media filed capacity and water requirement (Essam et al., 2013; Zarei et al., 2016). Salt treatment was performed within nine weeks from 23/7/2017­ to 26/9/2017. In addition, all of the plants were irrigated by distilled water for four months (26/1/2018). Stem length The length of the stem was recorded at the begin­ ning and end of the experiment. The difference between the two values was recorded as the differ­ ence in stem length (cm). Stem diameter The stem diameter was recorded at the beginning and end of the experiment by digital caliper (4 cm above the soil surface). The difference was recorded as the difference in stem diameter (mm). Number of leaves The number of expanded leaves was counted at Table 1 ­ The growth and bearing habit of studied fig cultivars (Sabet Sarvestani, 1999; Safai 2002; Jafari et al., 2016) Parameters Cultivar ‘Sabzʼ ‘Siyahʼ ‘Shah Anjirʼ ‘Atabakiʼ ‘Kashkiʼ ‘Matiʼ ‘Bar Anjirʼ Growth and bearing Relatively high High Moderate Moderate growth and low bearing High growth and moderate bearing Moderate growth and low bearing Low­ moderate growth and high bearing Bud Conical terminal buds with curved tip Curved and pointed terminal bud Terminal pointed bud Terminal conical bud Terminal conical, with tip Terminal conical bud without tip Terminal conical bud Fruit Medium, yellowish, no neck, thick pulp Medium, dark purple, no neck, thin skin, flesh uniformly red, low pulp thickness Large, necked, yellow, pink pulp, fully seed Large, rounded, reddish­purple fruit, reddish pulp, reddish Medium, green, , open ostiole necked, white pulp, low seedy Large, no neck, open ostiole, dark and thick fruit, white, reddish pulp Medium, with long neck, containing Blastophagous bees Type of consumption Dried Fruit Fresh fruit Both Fresh and dried fruit Fresh fruit Fresh and processed fruit Fresh fruit Caprifig Yield Very high High High Moderate Moderate Moderate Moderate Taste Excellent Sweet­and­sour Sweet Sweet­and­sour Sweet Sweet­and­sour Sweet Bearing period Early bearing Early bearing Mid­season bearing Early bearing Late bearing Early bearing Mid­season bearing Table 2 ­ Physico­chemical properties of the soil EC= Electrical conductivity; CEC= Cation exchange capacity. Soil texture San (%) Silt (%) Clay (%) EC (ds/m) CEC (Me/100) pH Lime (%) Sandy clay­loam 58±1.01 26±1 16±0.9 1.45±0.21 10.84±0.81 7.7±0.17 ±351.33 Organic C (%) N (%) K (ppm) P (ppm) Cu (ppm) Mn(ppm) Fe (ppm) Zn (ppm) 1.17±0.05 0.17±0.002 126±1.3 3.2±0.05 0.26±0.002 3.86±0.04 2.85±0.03 0.056±0.001 Adv. Hort. Sci., 2019 33(4): 553­565 556 the beginning and end of the experiment. The differ­ ence between the two values was recorded as the difference in the number of leaves. Specific leaf area (SLA), leaf dry matter content (LDMC) and leaf succulence The fourth top leaf was harvested after ending the experiment. The leaf area was recorded using a Leaf Area Meter (CI­202 Portable Laser Leaf Area Meter). The leaves were then dried in an oven (75°C, 48 hrs.) and the dry weight was recorded (LDW). The specific leaf area (in cm2 g­1) was calculated by using the Eq. (1). LDMC and leaf succulence were calculated using Eq. (2) and (3). SLA = LA/LDW (1) where LA is leaf area (cm2) and LDW is leaf dry weight (g), according to Hunt et al., 2002. LDMC = LDW/LFW (2) where LDW and LFW are leaf dry weight (g) and leaf fresh weight (g) respectively (Garnier et al., 2001). Leaf succulence = LFW/LA (3) where LFW is leaf fresh weight (g) and LA is leaf area (cm2), according to Agarie et al., 2007. Relative water content (RWC) Mature leaves were collected nine weeks after salt application at mid­day, and were transferred immediately to the lab. Then, five similar leaf discs without any vein were separated from each sample and weighted (W1). Further, the disc samples were placed in distilled water (4 hrs) under laboratory con­ ditions (24 ± 1oC). Subsequently, the samples were surface dried and re­weighed (W2). Furthermore, the discs were placed in an electric furnace (Model: Memmert, made by Karl Klob factory, Germany) (90°C, 60 min) and reweighted (W3). Finally, the rela­ tive water content was calculated using the Eq. (4) (Barrs and Weatherley, 1962). RWC = (W1 ­ W3) x 100 (4) (W2 ­ W3) Electrolyte Leakage (EL) The top expanded leaf was harvested and 5 leaf discs without any vein were prepared. The samples were rinsed three times with distilled water, and incu­ bated in 10 ml of distilled water (at 40°C for 30 min). After cooling, the electrical conductivity was mea­ sured using an Electrical Conductivity Meter (H18633 model) (C1). The samples were then autoclaved (at 120°C for 15 min). After cooling, the electrical conduc­ tivity was re­measured (C2). The Electrolyte Leakage was calculated via Eq. (5) (Sairam et al., 1997). EL = (C1/C2) x 100 (5) Leaf protein content First, the fresh leaf sample (0.2 g) was powdered with liquid nitrogen. Then, two ml of Potassium Phosphate buffer (38.5 ml NaH 2PO 4, 68.5 ml of Na2HPO4, 0.074 g EDTA and 1 g of PVP), pH = 7.15 was added and well­homogenized. The extract was cen­ trifuged at 13000 rpm for 15 min at 4°C, and the super­ natant was used to measure protein content. About 20 μl of the extract, 80 μl of potassium phosphate buffer (pH= 7.15) and 5 ml of Coomassie Brilliant Blue (C47H48N3NaO7S2) was stirred for 2 min. In addition, the absorbance was read at 595 nm by using a spec­ trophotometer (Biowave II model) after incubating 5 min at room temperature. The extraction buffer was used as Blank. The protein content (in mg g­1 FW) in the sample was calculated according to the sample absorp­ tion using the Bovine albumin serum (C123H193N35O37) standard curve (Bradford, 1976). Leaf nitrogen content The Kjeldahl method was used to determine the nitrogen content in fresh leaf samples (Kjeldahl, 1883). Photosynthetic indexes The photosynthetic indices were recorded using a compact­portable­photosynthesis­system (LCI, UK). The device was put on attached leaf (third expanded leaf) at midday, then transpiration rate (in mol H2O m­2 s­1) and stomata conductance (in mol CO2 m⁻² s⁻¹) w e r e r e c o r d e d a ft e r t w o m i n ( E v a n s a n d V o n Caemmerer, 1996). Experimental design and data analysis The present experiment was conducted in a Complete Randomized Design. The factors included fig cultivars (seven cultivars) and NaCl treatments (six concentrations), with five replications. SAS Version 9.1.3 (SAS®, 1990) was used for the statistical analy­ sis. Shapiro­Wilks test confirmed the normality of the data. In addition, Leven's test confirmed the variance homogeneity. Further, Tukey test was conducted for mean comparisons (P<0.01). Finally, Pearson coeffi­ c i e n t w a s u s e d f o r a n a l y z i n g t h e r e l a ti o n s h i p between the parameters. 3. Results The results of variance analysis indicated that the studied cultivars had a significantly different behavior Salimpour et al. ‐ Evaluating the salt tolerance of seven fig cultivars 557 3 leaves in the lowest and highest salinity levels in this cultivar. In addition, ‘Sabzʼ and ‘Atabakiʼ cultivars had the lowest number of leaves under intermediate salt conditions (4 and 6 dSm­1) (Table 4). The leaf number of ‘Atabakiʼ cultivar under higher salt condi­ tion was significantly lower than 0.5 dS m­1 of EC. Specific leaf area, leaf dry matter content and leaf succulence The specific leaf area followed a decreasing trend due to an increase in salt concentration in the ‘Sabzʼ, ‘Siyahʼ, ‘Shah Anjirʼ and ‘Kashkiʼ cultivars. In ‘Atabakiʼ cultivar, under EC of 6 and 10 dSm­1 the reduction was observed. In ‘Bar Anjirʼ cultivar, there was no sig­ nificant difference between 2­10 dsm­1 salt levels (Table 4). Except for ‘Matiʼ and ‘Bar Anjirʼ cultivars showing 32.21 and 60.55% increase in SLA, the rest of the cultivars had descending trend of SLA during the experiment. Leaf dry matter content of salt­ exposed fig cultivars followed a descending trend. The difference in LDMC of seven cultivars under low salt concentration (0.5 and 2 dsm­1) was not remark­ able. Under moderate salt condition (4 dsm­1), most of the cultivars had similar values but under higher salt (6 dsm­1 and more), ‘Shah Anjirʼ and ‘Siyahʼ culti­ vars showed an ascending trend. Leaf succulence dis­ played slight rising trend. ‘Bar Anjirʼ had the highest value under low salt conditions, while ‘Siyahʼ Showed the highest value under moderate and high salt con­ dition. The values of this parameter was unchanged under moderate salt conditions and the decrease started when NaCl reached 8 dsm­1 and more (Table 4). Leaf succulence of ‘Sabzʼ, ‘Shah Anjirʼ and ‘Siyahʼ under EC of 10 dS m­1 were 1.64, 1.64 and 1.61 times higher than their value under EC of 6 dSm­1. Relative water content of leaf Salinity had a significant effect on reducing leaf under salt conditions, due to salt concentration and cultivar variation (Table 3). Stem length W i t h i n c r e a s i n g s a l i n i t y l e v e l , s t e m l e n g t h decreased significantly in all cultivars. The greatest effect was observed in ‘Bar Anjirʼ cultivar, which decreased from 78.84 cm (under 0.5 dS m­1 salinity) to 28.44 cm (under 10 dS m­1 salinity). The lowest effect was observed in the ‘Siyahʼ cultivar, which reduced from 51.3 cm (in 0.5 dS m­1 salinity) to 35.8 cm (in 10 dS m­1 salinity) (Table 4). The decrease in stem length for all the tested cultivars was between low (0.5 dS m­1) and high (10 dS m­1) NaCl­treated plant. This decrease for most of the cultivars (includ­ ing ‘Sabzʼ, ‘Shah Anjirʼ, ‘Matiʼ and ‘Bar Anjirʼ) was more than 200%. Stem diameter By raising salinity, the stem diameter decreased significantly in all cultivars. The highest reduction in stem diameter was observed in the ‘Matiʼ cultivar, which decreased from 6.35 mm (under 0.5 dSm­1 salinity level) to 3.41 mm (under 10 dSm­1). The low­ est effect was observed in ‘Siyahʼ cultivar, reducing from 5.37 mm at the lowest salinity level to 3.2 mm at the highest salinity level (Table 4). In addition, the decrease in stem diameter of low and high salt treat­ ed plants varied between 157.93 to 219.89% (‘Kashkiʼ and ‘Bar Anjirʼ cultivars, respectively). Number of leaves With an increase in salinity levels, the number of leaves in all cultivars followed a decreasing trend. The greatest effect of salinity was observed in ‘Bar Anjirʼ, which difference in the number of the leaves in the lowest and highest salinity levels was 10.2 leaves. The lowest effect of salinity on leaf number was observed in ‘Shah Anjirʼ, and the difference was Table 3 ­ The interaction of cultivar and salinity on growth and physiological parameters of seven fig (the mean square value is given) NS, * and **= not significant, significant at 5 and 1% respectively (by Tukey mean comparison test). Physiological parameters Cultivar Salinity Cultivar x salinity Difference in stem length 1273.11 * 5916.23 * 223.68 ** Difference in stem diameter 9.61 ** 30.78 * 1.34 ** Difference in leaf number 107.80 ** 220.38 * 11.25 ** Specific Leaf Area 174.37 ** 27.628 NS 11.23 ** Relative water content 1540.57 ** 264.34 ** 289.57 ** Electrolyte Leakage 21.31 ** 239.41 ** 11.23 ** Leaf protein 37007542 ** 268172052 ** 4586351 ** Leaf nitrogen 0.93 ** 5.94 ** 0.071 ** Transpiration rate 4.46 ** 90.58 ** 3.89 ** Stomata conductance 0.099 ** 1.025 ** 0.074 ** 558 Adv. Hort. Sci., 2019 33(4): 553­565 relative water content in all cultivars. The highest decrease was observed in the ‘Siyahʼ cultivar, which reduced from 90.83% in the lowest salinity level to 53.03% in the highest salinity level. The lowest effect was observed on the ‘Sabzʼ cultivar. The intermediate salt condition of 4 dSm­1 did not make a significant difference from 2 dSm­1, except in ‘Sabzʼ (Table 5). The ‘Kashkiʼ and ‘Bar Anjirʼ cultivars had the lowest decline of RWC during the experiment (15.15 and 15.33%, respectively), while ‘Siyahʼ showed the stronger decrease in RWC (41.62%). Electrolyte leakage Salinity had a significant ascending effect on elec­ trolyte leakage in seven fig cultivars. The highest salini­ ty increased the ionic leakage in ‘Siyahʼ and ‘Atabakiʼ Table 4 ­ The influence of saline water on stem length, stem diameter, leaf number, specific leaf area, LDMC and leaf succulence of fig cultivars Genotype Treatments Stem length (cm) Stem diameter (mm) Leaf number Specific leaf area (cm2 g­1) LDMC Leaf succulence Sabz A 59.72 b 4.53 c 8.20 c 11.53 b 0.68 b 0.13 i B 48.00 c 3.19 d 6.80 d 13.38 a 0.70 b 0.11 i C 38.64 c 3.29 d 6.00 d 11.60 b 0.52 d 0.17 h D 27.90 d 2.34 e 4.00 e 11.76 b 0.57 c 0.15 h E 30.75 d 2.51 e 3.20 f 10.22 c 0.57 c 0.17 h F 27.30 d 2.39 e 2.60 f 7.85 e 0.52 d 0.24 g Siyah A 51.30 c 5.37 b 5.80 d 4.79 f 0.74 a 0.28 e B 38.80 c 4.91 c 4.60 d 3.64 g 0.73 a 0.38 d C 30.24 d 3.24 d 2.50 f 3.94 g 0.61 c 0.41 c D 36.50 d 3.87 d 3.40 f 3.76 g 0.60 c 0.44 c E 28.66 d 3.49 d 1.00 g 3.77 g 0.60 c 0.44 c F 35.80 d 3.20 d 2.50 f 2.04 g 0.69 b 0.71 a Shah anjir A 49.72 c 4.72 c 4.00 d 11.27 b 0.70 b 0.13 i B 52.40 c 5.27 b 6.40 d 11.04 b 0.54 d 0.17 h C 29.30 d 3.68 d 5.40 d 10.35 c 0.62 c 0.16 h D 32.90 d 3.60 d 2.60 f 9.73 c 0.74 a 0.14 h E 33.04 d 3.15 d 1.60 f 9.52 c 0.76 a 0.14 h F 23.06 d 2.54 e 1.00 g 6.40 e 0.69 b 0.23 g Atabaki A 76.50 a 4.75 c 7.60 c 11.89 b 0.71 b 0.12 i B 59.20 b 5.17 b 7.20 c 8.49 d 0.68 b 0.17 h C 53.74 c 4.56 c 6.60 d 7.76 e 0.61 c 0.21 g D 40.50 c 3.99 d 5.00 e 5.64 f 0.49 d 0.36 e E 25.30 d 1.45 f 3.00 f 8.82 d 0.44 e 0.26 g F 44.08 c 2.46 e 3.60 f 6.01 e 0.49 e 0.34 e Kashki A 78.00 a 5.18 b 12.40 a 9.55 c 0.61 c 0.17 h B 53.62 b 5.50 b 7.00 c 9.23 d 0.62 c 0.18 h C 50.14 c 3.77 d 8.00 c 9.08 d 0.52 d 0.21 g D 38.88 c 2.97 d 4.40 e 7.88 e 0.57 c 0.22 f E 46.02 c 3.26 d 3.80 f 6.75 e 0.57 c 0.26 g F 45.46 c 3.28 d 6.60 d 6.65 e 0.52 d 0.29 f Mati A 68.22 b 6.35 a 9.80 b 5.95 f 0.68 b 0.25 g B 64.80 b 5.80 b 9.60 b 8.55 d 0.62 c 0.19 h C 52.10 c 4.65 c 5.80 d 5.21 f 0.45 e 0.43 c D 38.30 c 4.19 c 3.20 f 4.64 f 0.45 e 0.48 c E 33.80 d 4.24 c 5.20 e 4.20 f 0.45 e 0.53 b F 30.90 d 3.41 d 2.40 f 7.86 e 0.44 e 0.29 f Bar anjir A 78.84 a 3.98 c 13.60 a 5.60 f 0.35 f 0.51 b B 58.00 b 4.02 c 11.00 b 8.36 d 0.29 f 0.41 c C 48.00 c 3.67 d 8.40 c 8.74 d 0.30 f 0.39 d D 43.56 c 3.19 d 7.40 c 8.98 d 0.32 f 0.35 e E 32.20 d 2.90 d 4.20 e 8.68 d 0.28 f 0.42 c F 28.44 d 1.81 e 3.40 f 8.99 d 0.30 f 0.38 e Data are average of five replications. In each column means with a common letter have no significant difference at 1% of Tukey test. Treatments A, B, C, D, E and F are 0.5, 2, 4, 6, 8, and 19 dS m­1 of EC, respectively. Salimpour et al. ‐ Evaluating the salt tolerance of seven fig cultivars 559 cultivars (Table 5). The electrolyte leakage of ‘Atabakiʼ, ‘Siyahʼ and ‘Bar Anjirʼ cultivars showed the highest dif­ ference between the moderate and high salt condi­ tions (39.19, 32.89 and 31.65% increases, respectively). Leaf protein The results indicated that salinity had a significant e ff e c t o n l e a f p r o t e i n o f s t u d i e d fi g c u l ti v a r s . Increasing the stress to 4 ds­1 of EC increased the Table 5 ­ The influence of saline water on electrolyte leakage, protein, nitrogen, transpiration rate, stomata conductance and RWC of fig cultivars Data are average of five replications. In each column means with a common letter have no significant difference at 1% of Tukey test. Treatments A, B, C, D, E and F are 0.5, 2, 4, 6, 8, and 19 dS m­1 of EC, respectively. Genotype Treatments RWC (%) Electrolyte leakage (%) Protein (mg. gˉ¹. Fw) Nitrogen content (%) Transpiration rate (mol H2O m ­2s­1) Stomata conductance (mol CO2 m⁻² s⁻¹) Sabz A 76.20 c 19.53 c 0.90 c 3.73 a 59.72 b 0.46 d B 74.80 c 20.75 c 0.93 c 3.55 b 48.00 d 0.13 g C 68.20 d 18.76 c 1.21 b 3.28 b 38.64 c 0.20 f D 62.55 d 17.80 d 1.79 b 3.13 b 27.90 c 0.20 f E 62.22 d 19.20 c 2.20 a 2.47 c 30.75 g 0.06 h F 61.88 d 22.01 c 2.45 a 2.31 c 27.30 g 0.05 h Siyah A 90.83 a 15.77 e 0.86 c 3.55 b 51.30 b 0.53 c B 76.78 c 16.42 d 0.86 c 3.59 b 38.80 c 0.78 a C 70.15 c 18.61 c 1.22 b 3.43 b 30.24 e 0.16 g D 67.55 d 19.91 c 2.17 a 3.21 b 36.50 e 0.14 g E 65.09 d 22.31 b 2.35 a 2.98 c 28.66 g 0.07 h F 53.03 e 24.73 a 2.60 a 2.97 b 35.80 g 0.04 h Shah anjir A 89.23 b 16.23 d 0.76 c 3.28 b 49.72 b 0.45 d B 88.79 b 15.17 e 0.92 c 3.28 b 52.40 b 0.48 d C 81.68 b 18.67 c 0.99 c 3.10 b 29.30 d 0.30 d D 77.66 c 21.24 b 1.01 b 2.50 c 32.90 d 0.15 g E 77.56 c 20.61 c 1.56 b 3.15 b 33.04 f 0.08 h F 72.15 c 22.22 c 1.36 b 2.92 c 23.06 e 0.11 g Atabaki A 81.16 b 14.37 e 0.91 c 3.13 b 76.50 a 0.67 b B 77.22 c 15.39 e 1.01 b 3.34 b 59.20 c 0.36 e C 75.33 c 16.56 d 1.15 b 3.16 b 53.74 d 0.38 d D 73.47 c 19.29 c 1.62 b 2.97 c 40.50 d 0.40 d E 71.09 c 22.75 b 2.04 a 2.43 c 25.30 g 0.06 h F 64.65 d 23.05 b 2.31 b 2.29 c 44.08 h 0.03 h Kashki A 85.34 b 16.51 d 0.74 c 2.98 c 78.00 b 0.40 a B 78.92 c 20.10 c 0.85 c 3.31 b 53.62 c 0.27 f C 75.33 c 20.04 c 1.08 b 3.13 b 50.14 e 0.13 g D 73.48 c 22.49 b 1.31 b 2.89 c 38.88 e 0.19 g E 73.29 c 23.20 b 1.84 b 2.75 c 46.02 e 0.14 g F 72.41 c 22.75 c 2.19 a 2.33 c 45.46 e 0.11 g Mati A 96.32 a 14.46 e 0.84 c 2.97 c 68.22 a 0.75 a B 88.58 b 17.27 d 0.94 c 3.50 b 64.80 b 0.43 d C 83.88 b 19.24 c 1.09 b 3.27 b 52.10 e 0.13 g D 78.39 c 21.22 b 1.23 b 3.09 b 38.30 e 0.23 f E 74.58 c 21.65 c 1.71 b 2.66 c 33.80 f 0.15 g F 70.23 c 22.38 c 2.01 a 2.60 c 30.90 g 0.04 h Bar anjir A 95.00 a 14.83 e 0.71 c 3.78 a 78.84 d 0.20 f B 93.68 a 15.30 e 0.75 c 3.32 b 58.00 d 0.34 e C 91.82 a 16.68 d 0.81 c 3.14 b 48.00 b 0.26 f D 88.52 b 19.72 c 1.04 b 2.82 c 43.56 b 0.09 h E 82.81 b 21.26 b 1.76 b 2.75 c 32.20 f 0.08 h F 80.44 b 21.96 c 1.96 b 2.30 c 28.44 g 0.04 h Adv. Hort. Sci., 2019 33(4): 553­565 560 total protein content gradually. The highest amounts were observed in ‘Siyahʼ (2.60 mg g­1 FW) and ‘Sabzʼ (2.45 mg g­1 FW) cultivars and the lowest in ‘Shah Anjirʼ (1.36 mg g­1 FW) and ‘Bar Anjirʼ (1.96 mg g­1 FW) cultivars (Table 5). The increase in protein content was expected between moderate (4 ds­1) and high (10 ds­1) NaCl treated plant. This increase for most of the cultivars (including ‘Sabzʼ, ‘Siyahʼ, ‘Atabakiʼ, ‘Kashkiʼ and ‘Bar Anjirʼ) was more than 200%. Leaf nitrogen By increasing salinity levels in all seven fig culti­ vars, leaf nitrogen content decreased. The highest reduction was observed in ‘Bar Anjirʼ cultivar at EC of 1 0 d s ­ 1 ( 2 . 3 0 % ) a n d t h e l o w e s t r e d u c ti o n w a s observed in ‘Siyahʼ cultivar, which decreased from 3.55% at the lowest salinity level to 2.99% at the EC o f 1 0 d S m ­ 1 ( T a b l e 5 ) . T h e ‘ M a ti ʼ , ‘ K a s h k i ʼ a n d ‘Atabakiʼ showed 10.03, 5.04 and 0.88% increase in N content under moderate salt condition (4 dSm­1), while the rest cultivars exhibited a decrease in N con­ tent (Table 5). Photosynthetic indices The interaction of salinity stress and cultivar on photosynthetic indices (transpiration rate and stoma­ ta conductance) was significant. With increasing NaCl levels, the rate of transpiration decreased in seven fig cultivars. The highest reduction was observed in ‘Atabakiʼ cultivar (0.85 mol H2O m ­2 s­1 at 10 dSm­1 of EC). The lowest influence was observed in ‘Kashkiʼ (3.41 mol H2O m ­2 s­1 at 10 dSm­1 of EC). For all the studied cultivars this parameter did not differ signifi­ cantly between 4 and 6 dSm­1 (intermediate salt con­ ditions). High salt concentrations (8 and 10 dSm­1) caused a noticeable difference among the genotypes, where ‘Atabakiʼ, ‘Siyahʼ, ‘Matiʼ and ‘Sabzʼ were fall to 12.18, 19.63, 22.16 and 23.40% of their initial values ( T a b l e 5 ) . S t o m a t a c o n d u c t a n c e d e c r e a s e d b y increasing salt concentration in all cultivars, and reached its lowest level at the highest salinity level (10 dSm­1). The lowest stomata conductance at of EC 10 dSm­1 was observed in ‘Atabakiʼ (0.03 mol CO2 m⁻² s⁻¹) and the lowest in ‘Kashkiʼ (0.11 mol CO2 m⁻² s⁻¹) (Table 5). The ‘Atabakiʼ, ‘Matiʼ and ‘Siyahʼ cultivars displayed the highest decrease of stomata conduc­ tance from 05. to 10 dSm­1of EC (3.86, 5.91 and 7.95% decrease of their initial values, respectively) Correlation analysis Table 4 indicates the bivariate Pearson correla­ tions among the parameters. The bold faces values indicate high correlated values (higher than 0.5). Difference in the number of leaves had high correla­ ti o n w i t h r e l a ti v e w a t e r c o n t e n t ( 0 . 5 8 3 * * ) , Transpiration rate (0.899**) and stomata conduc­ tance (0.915**). Specific leaf area and relative water content were positively correlated (0.680**). In addi­ tion, both photosynthetic indices showed high corre­ lation (0.877**) (Table 6). 4. Discussion and Conclusions The negative effect of salinity leads to the changes in soil structure, competition in nutrients uptake in different parts of the plant and eventually inhibition of nutrients absorption (Gholami et al., 2012). Na+ reduces plant biomass by disrupting the protein syn­ thesis, destroying chlorophyll, and decreasing the activity of the enzymes which are involved in biosyn­ Physiological parameters Leaf nitrogen Leaf protein Electrolyte Leakage Difference in stem length Difference in the number of leaves Difference in stem diameters Specific leaf area Relative water content Transpiration rate Stomata conduc­ tance Leaf nitrogen 1 Leaf protein ­0.170 * 1 Electrolyte Leakage ­0.225 ** 0.017 1 Difference in stem length ­0.375 ** ­0.006 0.068 1 Difference in the number of leaves 0.331 ** ­0.009 ­0.055 ­0.108 1 Difference in stem diameters ­0.415 ** 0.323 ** 0.179 ** 0.093 ­0.287 ** 1 Specific leaf area 0.393 ** ­0.239 ** ­0.103 ­0.079 0.199 ** ­0.480 ** 1 Relative water content 0.351 ** ­0.124 ­0.122 ­0.077 0.583 ** ­0.499 ** 0.680 ** 1 Transpiration rate 0.362 ** ­0.111 ­0.098 ­0.079 0.899 ** ­0.435 ** 0.227 ** 0.581 ** 1 Stomata conductance 0.195 ** 0.025 ­0.033 ­0.036 0.915 ** ­0.149* ­0.020 0.463 ** 0.877 ** 1 Table 6 ­ The correlation analysis of physiological parameters of fig cultivars * and **= Correlation is significant at the 5 and 1% levels, respectively. Salimpour et al. ‐ Evaluating the salt tolerance of seven fig cultivars 561 thesis (phosphoenolpyruvate carboxylase, Ribulose­ l,5­bisphosphate carboxylase, pentose phosphate pathway enzymes and glycolysis pathway enzymes) (Demiral, 2005). The major strategies of plants to overwhelm this stress included: reduction in Cl­ and Na+ uptake, leaf loss, decrease in leaf specific area and relative leaf water content, synthesis of osmotic compounds, exclusion of toxic ions into vacuole, change in mem­ brane stability, and increase in the activity of antioxi­ dant enzyme (Mutsushita and Matoch, 1992; Sato et al., 2006). Based on the results of the present study, the stem length in ‘Siyahʼ and ‘Sabzʼ was less affected by salt stress. In addition, under intermediate salt condi­ tions ‘Shah anjirʼ, ‘Siyahʼ and ‘Sabzʼ had the lowest stem length. It has already reported that salt­sensi­ tive fig cultivars such as ‘Brown Turkiʼ and ‘Piusʼ dis­ played reduction in stem length under salinity condi­ tions (Alswalmeh et al., 2015; Zarei et al., 2016). A similar decrease in stem length under salt conditions was reported in almond (Najafian et al., 2008) and pistachio (Adish et al., 2010). The findings of Soliman and Abd Alhady (2017) and Zarei et al. (2016), indicated that the stem diam­ e t e r i n s a l t ­ e x p o s e d fi g c u l ti v a r s h a d a l i n e a r decrease. Furthermore, the decrease in stem diame­ ter in salt­treated plums (Bolat et al., 2006), citrus (Khoshbahkt et al., 2014) and pomegranate (Khayyat et al., 2014) showed similar pattern. In the present study, stem diameter of ‘Siyahʼ cultivar was less affected by salt. Reducing the number of leaves in salt­exposed plants is due to limit leaf production or early leaf aging (Yeo et al., 1991; Munns and Tester, 2008). Based on the results, the highest leaf loss was observed in ‘Bar Anjirʼ cultivar. Similar results are available in almond (Momenpour et al., 2018), pista­ chio (Adish et al., 2010) and fig cultivars (Essam et al., 2013; Alswalmeh et al., 2015; Zarei et al., 2016; Soliman and Abd Alhady, 2017). Reduction in the relative leaf water content under salinity stress indicates lower water uptake by plants. Limited access to water due to increase in osmotic potential reduces the cell development and decreas­ e s t u r g o r p r e s s u r e o f t h e c e l l s ( Y a m a s a k i a n d Dillenburg, 1999). In the present study, salinity reduced the relative content of leaf water in fig culti­ vars, except ‘Bar Anjirʼ. In ‘Siyahʼ cultivar, a dramatic decrease was observed in the relative leaf water con­ tent. Under various salt concentrations, the trend of this parameter stayed unchanged. Under intermediate salt conditions the specific leaf area of ‘Siyahʼ and ‘Sabzʼ had not evident changes. According to Owais (2015), with increasing salt levels, the relative leaf water content in grape genotypes decreased, but this decrease was lower in tolerant cultivars. A similar decrease was observed in the relative leaf water content under salinity stress in fig (Zarei et al., 2016; Soliman and Abd Alhady, 2017) and pomegranate (Khayyat et al., 2014). The values of SLA and LDMC reveal an important exchange in plant function between high SLA, low LDMC (cultivars with rapid production of biomass) and low SLA, high LDMC (cultivars with an efficient conservation of nutrients) (Poorter and Garnier, 1999). According to our results, ‘Siyahʼ and ‘Sabzʼ cul­ tivars had the lowest SLA and the highest LDMC value, confirmed its production efficiency under vari­ ous salt concentration. In addition, ‘Bar Anjirʼ and ‘Shah Anjirʼ had the highest SLA and the lowest LSDM under different NaCl concentration, due to their lim­ ited production efficiency under salt conditions. Rising the salinity level, increased leaf succulence. This ability characterizes a balance between growth rate and the necessity of osmotic adjustments (Flowers and Yeo, 1986), which regulate low external w a t e r p o t e n ti a l e n c o u r a g e d b y s a l i n i t y s t r e s s (Flowers and Colmer, 2008). Moreover, it explains the better carbon assimilation capacity per unit area (de Vos et al., 2013). Based on our findings ‘Siyahʼ and ‘Sabzʼ cultivars had the highest leaf succulence, which related to the balance between growth ratio and osmotic regulation under salt conditions. Peroxidation of lipids is regarded as an extra effect of salinity on plants (Demidehik et al., 2002). The findings of the previous researchers on increas­ ing ion leakage under salinity stress in fig (Abdoli Nejad and Shekhafandeh, 2014; Zarei et al., 2016) and pomegranate (Khayyat et al., 2014) confirms our results. Proteins biosynthesis is an important biochemical process which is affected by salt stress. Expression of specific genes under NaCl stress assistances the plant to adapt to adverse conditions (Murcute et al., 2010). According to our findings, protein content increased under high salt condition, but this increase was greater under intermediate salt for ‘Siyahʼ and ‘Sabzʼ cultivars. It has reported that sodium chloride treatment reduced leaf protein content in salt­sensitive grape (Alizadeh et al., 2010) and figs (Abdoli Nejad and Shekhafandeh, 2014). In fact, salt inhibits the synthesis of nitrate reduc­ Adv. Hort. Sci., 2019 33(4): 553­565 562 tase, glutamine synthase and glutamate synthase ( w h i c h a r e i n v o l v e d i n n i t r o g e n m e t a b o l i s m ) , decreases nitrogen metabolism (Hossain et al., 2012), changes active forms of nitrogen, reduces amino acids synthesis, and finally increases the activity of degrading enzymes (De Souza et al., 2016). In saline conditions, Cl­ competes with nitrate (Abdelgadir et al., 2005), leading to the decline of nitrogen in differ­ ent parts of the plant (Yu et al., 2016; Hasan and Miyake, 2017). According to the Owais (2015) and Doulati Baneh et al. (2014), salinity had a decreasing effect on the leaf nitrogen content in fruit crops. Although the relationship between salinity and nitro­ gen metabolism is very complex, balanced nitrogen metabolism significantly affects salinity tolerance in plants (Teh et al., 2016). In the present study, the impact of salinity on leaf nitrogen content of differ­ ent fig cultivars was not the same. Photosynthesis is another important plant phe­ nomenon, significantly affected by abiotic stress. Reduction of photosynthesis under salinity stress is attributed to stomata factors (reduced CO2 perme­ ability, stomata closure, decrease in plants transpira­ tion, stomata conductance reduction), and non­stom­ ata factors (cell membrane dehydration, structural changes in the cytoplasm and chlorophyll degrada­ tion) (Brugnoli and Lauteri, 1991; Reza et al., 2006; Tabatabaei, 2006). Salinity reduces stomata conduc­ tance in hybrids of fig, by decreasing the photo­con­ ductivity of leaf cells (Golombek and Lüdders, 1990; Zarei et al., 2016), which is in agreement with the results of the present study. Similar results were reported in pistachio (Adish et al., 2010). According to the results of the present study, ‘Atabakiʼ and ‘Kashkiʼ cultivars showed the lowest and the highest stomata conductance under high salt condition, respectively. Salinity reduces evaporation and transpiration in plants (Bhantana and Lazarovitch, 2010; Dudley et al., 2008). The linear relationship among reduction of plant evapotranspiration, transpiration and increase in salinity levels was reported in pomegranate (Shani and Ben­Gal, 2005; Mohamed Ibrahim and Abd El­Samad, 2018) and date palm (Tripler et al., 2007), which is coordinated with the results of the current study. In addition, the maximum quantum efficiency of photosystem II, electron transfer, gas exchange, and carbon dioxide assimilation decrease under salt con­ ditions (Joao­Correia et al., 2006). In the present study, Atabaki cultivar had the highest transpiration rate at the low and mild salinity levels, and with increasing salinity, a greater decrease was observed (Table 5). The lowest effect of salinity on transpira­ tion rate was observed in ‘Kashkiʼ (Table 5), the culti­ var which was able to balance the transpiration level at mild and severe stress levels, probably due to hav­ ing thicker cuticle. The most important physiological process affected by this stress is photosynthesis (Sudhir and Murthy, 2004; Acosta­Motos et al., 2017). Reduction in pho­ tosynthesis efficiency is followed by a series of mole­ cular events including cell membrane dehydration, stomata closure, decreased CO2 entry, reduction in leaf permeability to CO2, structural changes in the cytoplasm and subsequent alteration in the activity of enzymes (Tabatabaei, 2006). On the other hand, nitrogen plays effective role in plant growth and construction of vital plant struc­ tures such as amino acids and proteins (Arghavani et al., 2017). Nitrogen is necessary to generate cellular components such as Rubisco, which is responsible for assimilating carbon dioxide. Therefore, by limiting nitrogen uptake, salinity stress affects the photosyn­ thesis efficiency, leading to a decrease in vegetative and reproductive growth (Coruzzi and Bush, 2001; Marschner, 2012; Zarata­Valdez et al., 2015). In the present research, salinity had a significant effect on growth parameters and photosynthetic indices in seven cultivars of fig. The differences in stem length, stem diameter and leaf number in all cultivars followed a downward trend. The stomata conductance of all fig cultivars was same up to 4 dS m­1 NaCl. Moreover, the transpiration rate did not exhibited variation unless in salt concentration higher than 8 dSm­1. The ‘Siyahʼ and ‘Sabzʼ cultivars had the lowest decreases in stem length and diameter, the lowest leaf water content and transpiration rate, and the maximum leaf abscission. Additionally, ‘Siyahʼ and ‘Sabzʼ cultivars had the highest leaf succulence and LDMC and the lowest SLA, which related to the balance between growth ratio and osmotic regula­ tion under salt conditions. The ‘Matiʼ, as an interme­ diate salt­tolerance cultivar, had the lowest leaf abscission under severe salinity levels. 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