Durum wheat seedling responses to simultaneous high light and salinity involve a fine reconfiguration of amino acids and carbohydrate metabolism

Durum wheat plants are extremely sensitive to drought and salinity during seedling and early development stages. Their responses to stresses have been extensively studied to provide new metabolic targets and improving the tolerance to adverse environments. Most of these studies have been performed in growth chambers under low light [300–350 µmol m^?2 s^?1 photosynthetically active radiation (PAR), LL]. However, in nature plants have to face frequent fluctuations of light intensities that often exceed their photosynthetic capacity (900–2000 µmol m^?2 s^?1). In this study we investigated the physiological and metabolic changes potentially involved in osmotic adjustment and antioxidant defense in durum wheat seedlings under high light (HL) and salinity. The combined application of the two stresses decreased the water potential and stomatal conductance without reducing the photosynthetic efficiency of the plants. Glycine betaine (GB) synthesis was inhibited, proline and glutamate content decreased, while γ‐aminobutyric acid (GABA), amides and minor amino acids increased. The expression level and enzymatic activities of Δ1‐pyrroline‐5‐carboxylate synthetase, asparagine synthetase and glutamate decarboxylase, as well as other enzymatic activities of nitrogen and carbon metabolism, were analyzed. Antioxidant enzymes and metabolites were also considered. The results showed that the complex interplay seen in durum wheat plants under salinity at LL was simplified: GB and antioxidants did not play a main role. On the contrary, the fine tuning of few specific primary metabolites (GABA, amides, minor amino acids and hexoses) remodeled metabolism and defense processes, playing a key role in the response to simultaneous stresses.     

Application of homobrassinolide enhances growth,yield and quality of tomato

Brassinosteroids (BRs) have emerged as pleiotropic phytohormone owing to their wide function in crop growth and metabolism. Homobrassinolide (HBR) being an analogue of BRs is known to improve the growth, yield and quality parameters in many crop plants. Thus, an evaluation study was conducted for two years (2018 and 2019) to elucidate the performance of tomato plants (Solanum lycopersicum L.) to a novel group of phytohormone,HBR. The field experiment comprised of seven treatments with homobrassinolide 0.04% (Emulsifiable Concentrate) EC at four different concentrations (0.06, 0.08, 0.10 and 0.12 g active ingredient (a.i.) ha^?1) and two well-known growth promoters viz., Gibberellic acid (GA), Naphthalene Acetic Acid (NAA) along with the untreated control. Plant height and chlorophyll concentration were found significantly different in both years of experiment as well as among the different treatments. HBR at 0.12 g a.i. ha^?1 was found better with maximum number of fruits (77.36 plant^?1), fruit length (6.72 cm), fruit breadth (6.45 cm) and fruit weight (80.52 g) over other concentrations and treatments. Fruit yield was more pronounced in the plots treated with plant growth regulators compared to untreated control. However, significantly higher fruit yield of 91.07 t ha^?1 (62.58 t ha^?1 with untreated control) along with improved quality traits viz., fruit firmness (4.11 kg cm^?2), ascorbic acid content (24.09 mg 100 g^?1), total soluble solids (4.43°Brix) and keeping quality (12.50 days) was recorded in 0.12 g a.i. ha^?1 HBR treated plots. Thus, it can be inferred that HBRapplication would be a better option to enhance growth, yield as well as quality traits in tomato.     

Photosynthesis, photorespiration and productivity of wheat and soybean genotypes

The results of the numerous measurements obtained during the last 40 years on gas exchange rate, photosynthetic carbon metabolism by exposition in ¹⁴CO₂ and activities of primary carbon fixation enzyme, ribulose‐1,5‐bisphosphate carboxylase/oxygenase (RuBPC/O), in various wheat and soybean genotypes grown over a wide area in the field and contrasting in photosynthetic traits and productivity are presented in this article. It was established that high productive wheat genotypes (7–9 t ha^?1) with the optimal architectonics possess higher rate of CO₂ assimilation during the leaf ontogenesis. Along with the high rate of photosynthesis, high values of photorespiration are characteristic for the high productive genotypes. Genotypes with moderate (4–5 t ha^?1) and low (3 t ha^?1) grain yield are characterized by relatively low rates of both CO₂ assimilation and photorespiration. A value of photorespiration constitutes 28–35% of photosynthetic rate in contrasting genotypes. The activities of RuBPC and RuBPO were changing in a similar way in the course of the flag leaf and ear elements development. High productive genotypes are also characterized by a higher rate of biosynthesis and total value of glycine–serine and a higher photosynthetic rate. Therefore, contrary to conception arisen during many years on the wastefulness of photorespiration, taking into account the versatile investigations on different aspects of photorespiration, it was proved that photorespiration is one of the evolutionarily developed vital metabolic processes in plants and the attempts to reduce this process with the purpose of increasing the crop productivity are inconsistent.     

Growth and pigment content of wheat as influenced by the combined effects of salinity and growth regulators

A field experiment was conducted to investigate the effects of presoaking the wheat grains (Triticum aestivum L.) in different levels of salinity (33 or 66 mM) and in growth regulators (indolyl-3-acetic acid, IAA at SO g m^-3, gibberellic acid, GA₃ at 100 g m^-3, or kinetin at 100 g m_-3) on the shoot growth and pigment content of the developing wheat flag leaf. Salinity at 33 or 66 mM led to an insignificant increase in the fresh and dry masses as well as in the shoot diameter and shoot length, but it attenuated the flag leaf area. In the majority of cases, salinity increased the chlorophyll (Chla, Chlb) and carotenoid contents as well as the number of chloroplasts per a mesophyll cell. The growth in the wheat shoot of the saline-treated plants was, in general, stimulated in response to presoaking the grains in kinetin or GA₃. On the other hand, IAA + salinity led to a negligible effect on the growth in the wheat plants particularly at the early stages of growth. The presoaking of grains in NaCl at 33 mM + IAA or 66 mM + kinetin induced a marked increase in the pigment content of the wheat flag leaf particularly at the early stages of growth. The interaction between salinity and phytohormones increased the number of chloroplasts; kinetin was the most effective.     

盐胁迫下小麦甜菜碱和脯氨酸含量变化

运用高效液相色谱-质谱(HPLC-MS)联用技术分析了耐盐性强、中、弱3个小麦品种SW12、宁春4号和中国春苗期5个NaCl浓度胁迫下甜菜碱和脯氨酸含量的变化.方差分析表明盐胁迫下3个小麦品种之间甜菜碱的含量差异达到极显著水平(P＜0.01),SW12的含量最高,宁春4号次之,中国春最低,与小麦耐盐性表现相一致;脯氨酸在叶片中的含量差异不显著,在根中宁春4号和中国春的含量有显著差异(P＜0.05).结果表明:小麦叶和根中甘氨酸甜菜碱含量与小麦盐胁迫呈正相关,是小麦体内抵御盐胁迫的渗透调节物质之一,可作为小麦耐盐性鉴定指标.     

Hormones-induced modifications in the response of wheat flag leaf to NaCl

A field experiment was carried out to investigate the effects of presoaking the wheat grains (Triticum aestivum L.) in 33 or 66 mM NaCl and indolyl-3-acetic acid (IAA at 50 g m⁻³), gibberellic acid (GA₃ at 100 g m⁻³) or kinetin (100 g m⁻³) on some tolerance criteria in wheat flag leaf at different stages of development. At various stages of flag leaf development pretreatment with 33 or 66 mM NaCl decreased degree of succulence (particularly 66 mM), relative growth rate, net assimilation rate, relative water content, K⁺ content and K⁺/Na⁺ ratio and at the same time induced accumulation of abscisic acid and Na⁺. In the majority of cases grain pretreatment with GA₃ or kinetin and to a lesser extent with IAA alleviated either partially or completely the deleterious effect of salinity on the above mentioned parameters.     

24-Epibrassinolide alleviates salt-induced inhibition of productivity by increasing nutrients and compatible solutes accumulation and enhancing antioxidant system in wheat (Triticum aestivum L.)

Two wheat (Triticum aestivum L.) cultivars, Sids 1 and Giza 168, were grown under non-saline or saline conditions (4.7 and 9.4 dS m^?1) and were sprayed with 0.00, 0.05 and 0.10 mg l^?1 24-epibrassinolide (EBL). Salt stress markedly decreased plant productivity and N, P, and K uptake, particularly in Giza 168. A follow-up treatment with 0.1 mg l^?1 EBL detoxified the stress generated by salinity and considerably improved the above parameters, especially in Sids 1. Organic solutes (soluble sugars, free amino acids, proline and glycinebetaine), antioxidative enzymes (superoxide dismutase, peroxidase, catalase and glutathione reductase), antioxidant molecules (glutathione and ascorbate) and Ca and Mg levels were increased under saline condition, and these increases proved to be more significant in salt-stressed plants sprayed with EBL, particularly at 0.1 mg l^?1 EBL with Sids 1. Sodium concentration, lipid peroxidation, hydrogen peroxide content and electrolyte leakage were increased under salt stress and significantly decreased when 0.1 mg l^?1 EBL was sprayed. Clearly, EBL alleviates salt-induced inhibition of productivity by altering the physiological and biochemical properties of the plant.     

Physiological changes in soybean (Glycine max) Wuyin9 in response to N and P nutrition

Phosphorus deficiency is a very common problem in the acid soil of central China. Previous research has shown that starter N and N topdressing at the flowering stage (Rl) increased soybean (Glycine max) yield and N₂ fixation (Gan et al, 1997, 2000). However, there is little information available concerning soybean response to P‐fertiliser in soybean production in central China (Gan, 1999). A field experiment was conducted to investigate the response to P (0 kg P ha^?1, 22 kg P ha^?1, 44 kg P ha^?1 before sowing) and N fertiliser application (N1: 0 kg N ha^?1, N2: 25 kg N ha^?1 before sowing, N3: N2 + 50 kg N ha^?1 at the V2 stage and N4: N2 + 50 kg N ha^?1 at the R1 stage) on growth, yield and N₂ fixation of soybean. Both N and P fertiliser increased growth and seed yield of soybean (P < 0.01). Application of basal P fertiliser at 22 kg P ha^?1 or 44 kg P ha^?1 increased total N accumulation by 11% and 10% (P < 0.01) and seed yield by 12% and 13% (P < 0.01), respectively, compared to the zero P treatment. Although application of starter N at 25 kg N ha^?1 had no positive effect on seed yield at any P level (P > 0.05), an application of a topdressing of 50 kg N ha^?1 at the V2 or R1 stage increased total N accumulation by 11% and 14% (P < 0.01) and seed yield by 16% and 21% (P < 0.01), respectively, compared to the zero N treatment. Soybean plants were grown on sterilised Perlite in the greenhouse experiment to study the physiological response to different concentrations of phosphate (P1: 0 mM; P2: 0.05 mM; P3: 0.5 mM; P4:1.0 mN) and nitrate (N1: 0 mM with inoculation, N2: 20 mM with inoculation). The result confirmed that N and P nutrients both had positive effects on growth, nodulation and yield (P < 0.01). The relative importance of growth parameters that contributed to the larger biomass with N and P fertilisation was in decreasing order: (i) total leaf area, (ii) individual leaf area, (iii) shoot/root ratio, (iv) leaf area ratio and (v) specific leaf area. The yield increase at N and P supply was mainly associated with more seeds and a larger pod number per plant, which confirmed the result from the field experiment.     

Betaine status in wheat in relation to nitrogen stress and to transient salinity stress

Summary Glycine betaine is readily accumulated in wheat (Triticum aestivum cv. Inia) shoots during periods of salinity stress. The ability of the plant to utilize betaine as a source of nitrogen remains unresolved. We, therefore, conducted solution culture experiments in a greenhouse to test the hypothesis that betaine is degraded in wheat shoots under conditions of severe nitrogen deficiency. Betaine concentrations increased in continuously salt stressed plants for only 17 days after salinity was imposed. After this period, concentrations (dry weight basis) decreased steadily until plants died 32 days later. Decreases in betaine concentration were also observed in treatments where salinity stress was removed. The rate of decrease in concentration was greatest in the N-free treatment. These decreases in betaine concentration were the result of dilution by plant growth. Betaine contents (mol shoot^–1) remained unchanged after removal of substrate nitrate. Therefore our results support the hypothesis that betaine is a stable end product of metabolism.     

Drought-tolerant endophytic actinobacteria promote growth of wheat (Triticum aestivum) under water stress conditions

Drought tolerant endophytic actinobacteria Streptomyces coelicolor DE07, S. olivaceus DE10 and Streptomyces geysiriensis DE27 were isolated from cultivated plants of arid and drought affected regions of Rajasthan, India. These isolates exhibited plant growth promotion traits and intrinsic water stress tolerance from ?0.05 to ?0.73 MPa. Maximum auxin production was observed in majority of actinobacterial cultures in the logarithmic to stationary phase of growth. Significant enhancement of wheat seedling vigour was recorded by the inoculation of these endophytic actinobacteria. S. olivaceus DE10 recorded maximum accumulation of indole 3-acetic acid (84.34?μg?mg^?1 protein). Culture and cell-free extract of the endophytes was applied on to wheat seeds to assess the effect on growth in water-stressed soil. Maximum yield was recorded with the inoculation of S. olivaceus DE10 culture (492.77?kg?ha^?1) and cell-free extract (262.31?kg?ha^?1). Co-inoculation of S. olivaceus DE10?+?S. geysiriensis DE27 recorded highest yield of 550.09?kg?ha^?1 while their cell-free extract yielded 524.92?kg?ha^?1. Overall, wheat seeds treated with cultures showed better plant growth and yield in comparison to control. Direct coating of cultures on seeds yielded better performance than cell-free extract coated on seeds and co-inoculation of cultures or cell-free extract proved better than single culture inoculations. Production of phytohormones, plant growth promotion traits combined with water stress tolerance potential in these endophytic actinobacteria played a cumulative synergistic role that supported enhanced plant growth promotion of wheat in the stressed soil.     

Regulation of Nitrogen Metabolism,Photosynthetic Activity,and Yield Attributes of Spring Wheat by Nitrogen Fertilizer in the Semi-arid Loess Plateau Region

It is critical for spring wheat (Triticum aestivum L.) production in the semi-arid Loess Plateau to understand the impact of nitrogen (N) fertilizer on changes in N metabolism, photosynthetic parameters, and their relationship with grain yield and quality. The photosynthetic capacity of flag leaves, dry matter accumulation, and N metabolite enzyme activities from anthesis to maturity were studied on a long-term fertilization trial under different N rates [0 kg ha^?1(N1), 52.5 kg ha^?1 (N2), 105 kg ha^?1 (N3), 157.5 kg ha^?1 (N4), and 210 kg ha^?1 (N5)]. It was observed that N3 produced optimum total dry matter (5407 kg ha^?1), 1000 grain weight (39.7 g), grain yield (2.64 t ha^?1), and protein content (13.97%). Our results showed that N fertilization significantly increased photosynthetic parameters and N metabolite enzymes at all growth stages. Nitrogen harvest index, partial productivity factor, agronomic recovery efficiency, and nitrogen agronomic efficiency were decreased with increased N. Higher N rates (N3–N5) maintained higher photosynthetic capacity and dry matter accumulation and lower intercellular CO₂ content. The N supply influenced NUE by improving photosynthetic properties. The N3 produced highest chlorophyll content, photosynthetic rate, stomatal conductance and transpiration rate, grain yield, grain protein, dry matter, grains weight, and N metabolite enzyme activities compared to the other rates (N1, N2, N4, and N5). Therefore, increasing N rates beyond the optimum quantity only promotes vegetative development and results in lower yields.

     

Salinity and drought interaction in wheat (Triticum aestivum L.) is affected by the genotype and plant growth stage

Salinity and drought are important agro-environmental problems occurring separately as well as together with the combined occurrence increasing with time due to climate change. Screening of bread wheat genotypes against salinity or drought alone is common; however, little information is available on the response of wheat genotypes to a combination of these stresses. This study investigates the response of a salt-resistant (SARC-1) and a salt-sensitive (7-Cerros) wheat genotype to drought at different growth stages under non-saline (ECe 2.1 dS m^?1) and saline soil (ECe 15 dS m^?1) conditions. Drought was applied by withholding water for 21 days at a particular growth stage viz. tillering, booting, and grain filling stages. At booting stage measurements regarding water relations, leaf ionic composition and photosynthetic attributes were made. At maturity grain yield and different yield, components were recorded. Salinity and drought significantly decreased grain yield and different yield components with a higher decrease in the case of combined stress of salinity × drought. The complete drought treatment (drought at tillering + booting + grain filling stages) was most harmful for wheat followed by drought at booting stage and grain filling–tillering stages, respectively. The salt-resistant wheat genotype SARC-1 performed better than the salt-sensitive genotype 7-Cerros in different stress treatments. A decrease in the water and turgor potentials, photosynthetic and transpiration rates, stomatal conductance, leaf K⁺, and increased leaf Na⁺ were the apparent causes of growth and yield reduction of bread wheat due to salinity, drought, and salinity × drought.     

Microbial Utilization of Glycine Betain in Hypersaline Soda Lakes

Microbiology - Glycine betaine (GB) is a biologically important compound for microbial communities living in saline habitats most commonly employed as an organic osmolyte. At fluctuating salinity,...     

Soil salinity effects on transpiration and net photosynthetic rates,stomatal conductance and Na+ and Cl− contents in durum wheat

Leaf gas exchange, plant growth and leaf ion content were measured in wheat (Triticum durum L. cv. HD 4502) exposed to steady- state salinities (1.6, 12.0 and 16.0 dS nr⁻¹) for 8 weeks. Salinity reduced leaf area and number of tillers, and increased Na⁺ and Cl⁻ concentrations in leaves. Leaf- to- leaf gradients of these ions were observed. The oldest leaf contained 6 to 8 times more Na⁺ and Cl⁻ than the flag leaf. Net photosynthetic rate (P_N), transpiration rate (E) and stomatal conductance (g_S) were the highest in flag leaf, declined in the middle and fully expanded leaves, and were minimum in the oldest leaves. These processes were reduced by salinity with similar leaf- to- leaf gradients. Intercellular CO₂ concentrations in the older leaves were higher than in the flag leaf in non-saline plants, and increased similarly with salinity. Leaf age was the major factor in reducing P_N, and senescence processes were promoted by salinity.     

Alleviation of salinity-induced perturbations in ionic and hormonal concentrations in spring wheat through seed preconditioning in synthetic auxins

The experiments were conducted to examine the effects of seed priming in solutions (100, 150 and 200 mg L^?1) of different synthetic auxins, i.e., 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), α-naphthaleneacetic acid (NAA) on growth, grain yield, gaseous exchange characteristics, ionic and hormonal concentrations in two spring wheat (Triticum aestivum L.) cultivars MH-97 (salt intolerant) and Inqlab-91 (salt tolerant). The primed (soaked for 12 h) and non-primed seeds were sown in Petri plates in a growth room as well as in a field treated with 150 mM NaCl. Generally, all synthetic auxins did not increase germination percentage and rate in both cultivars when compared with hydropriming (control), and even decreased these attributes when applied at higher concentrations (200 mg L^?1). Nonetheless, under salt stress, NAA (150 mg L^?1) was most effective in increasing seedling shoot dry weight, fertile tillers per plant, number of grains per ear and grain yield in both cultivars. The plants raised from seed treated with NAA (150 mg L^?1) had lower shoot [Na⁺] in the salt intolerant cultivar. Moreover, NAA treatment improved root [Ca²⁺] in both cultivars. Priming agents affected leaf free indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) concentrations differently in both cultivars. Treatment with NAA (150 mg L^?1) lowered leaf free abscisic acid (ABA) and putrescine (Put) concentrations and raised salicylic acid (SA) and spermidine (Spd) concentrations in the salt intolerant cultivar. In conclusion, pre-treatment with NAA (150 mg L^?1) showed consistent promotive effects on growth and grain yield in the two cultivars, which were partially attributed to the beneficial effects of NAA-priming on ionic and hormonal homeostasis under salt stress.     

Glycine betaine accumulation,ionic and water relations of red-beet at contrasting levels of sodium supply

Exposure of plants to sodium (Na) and salinity may increase glycine betaine accumulation in tissues. To study this, red-beet cvs. Scarlet Supreme and Ruby Queen, were grown for 42 days in a growth chamber using a re-circulating nutrient film technique with 0.25 mmol/L K and either 4.75 mmol/L (control) or 54.75 mmol/L (saline) Na (as NaCl). Plants were harvested at weekly intervals and measurements were taken on leaf water relations, leaf photosynthetic rates, chlorophyll fluorescence, chlorophyll levels, glycine betaine levels, and tissue elemental composition. Glycine betaine accumulation increased under salinity and this accumulation correlated with higher tissue levels of Na in both cultivars. Na accounted for 80 to 90% of the total cation uptake under the saline treatment. At final harvest (42 days), K concentrations in laminae ranged from approximately 65-95 micromoles g-1 dry matter (DM), whereas Na in shoot tissue ranged from approximately 3000-4000 micromoles g-1. Leaf sap osmotic potential at full turgor [psi(s100)] increased as lamina Na content increased. Glycine betaine levels of leaf laminae showed a linear relationship with leaf sap [psi(s100)]. Chlorophyll levels, leaf photosynthetic rates, and chlorophyll fluorescence were not affected by Na levels. These results suggest that the metabolic tolerance to high levels of tissue Na in red-beet could be due to its ability to synthesize and regulate glycine betaine production, and to control partitioning of Na and glycine betaine between the vacuole and the cytoplasm.     

Contribution of the wheat (Triticum aestivum L.) flag leaf to grain yield in response to plant growth regulators

In West-Europe, intensive cereal management uses plant growth regulators (PGRs) especially for wheat. A green-house experiment compared the effects of two PGRs on flag leaf characteristics and yield of winter wheat. Chlormequat chloride + choline chloride (CCC) and chlormequat chloride + choline chloride + imazaquin (CCC+I) were applied to winter wheat at growth stage 5 (Feekes Large scale). CCC and CCC+I significantly increased flag leaf surface area at anthesis. Both treatments also enhanced chlorophyll content of the main stem flag leaf. The grain filling period was extended with PGR application by 2 days. CCC and CCC+I significantly increased net CO₂ assimilation rates during the flag leaf life. No effects of PGR spraying were observed on the pattern of ¹⁴C labelled assimilate distribution. Increased grain yield was due to the increase in average grain weight. The results indicate that PGR treatments increased flag leaf contribution to grain filling. The addition of imazaquin (I) to chlormequat (CCC) improved the effects of CCC.     

Influence of salt stress on seed yield and oil quality of two sunflower hybrids

Sunflower is a major oil seed crop worldwide, and it is also an important crop in Mediterranean areas where salinity is an increasing problem. In this paper, the effect of saline irrigation water on seed yield and quality of sunflower was evaluated. A pot experiment was carried out over two crop seasons on two hybrids – a standard one (Carlos) and a high oleic one (Tenor) – submitted to five salinity levels of irrigation water (0.6, 3, 6, 9 and 12 dS m^?1). Soil salinity was monitored over the entire crop cycle, and leaf ion content was determined at maturity. Tenor showed higher Na⁺ and Mg²⁺ content but lower K⁺ values. No difference between the two hybrids was observed for Cl^? content. A progressive increase in leaf Na⁺, K⁺ and Cl^? contents and Na⁺/K⁺ ratio with increasing salinity level was observed. Seed weight per head, 1000 achene weight, number of seeds per plant and oil yield significantly decreased under salt stress in both hybrids. The percent seed yield decrease was higher per unit increase in electrical conductivity of irrigation water, ECw (8%), than per unit increase in electrical conductivity of saturated‐soil extracts, ECe (5%). Concerning oil fatty acid composition, the main significant difference as result of salt stress was a progressive increase in oleic acid content, from 82.2% to 86.7% for Tenor and from 21.8% to 27.3% for Carlos, which was consistent with a decrease in linoleic acid content, from 5.9% to 3% for Tenor and from 66% to 61.3% for Carlos. These results confirm the possible inhibition of oleate desaturase under salt stress.     

Modulation of nutrient acquisition and polyamine pool in salt-stressed wheat (Triticum aestivum L.) plants inoculated with arbuscular mycorrhizal fungi

Two wheat (Triticum aestivum L.) cultivars, Sids 1 and Giza 168, were grown under non-saline or saline conditions (4.7 and 9.4 dS m^?1) with and without arbuscular mycorrhizal fungi (AMF) inoculation. Salt stress considerably decreased root colonization, plant productivity and N, P, K⁺, Fe, Zn and Cu concentrations, while it increased Na⁺ level, particularly in Giza 168. Mycorrhizal colonization significantly enhanced plant productivity and N, P, K⁺, Fe, Zn and Cu acquisition, while it diminished Na⁺ uptake, especially in Sids 1. Salinity increased putrescine level in Giza 168, however, values of spermidine and spermine increased in Sids 1 and decreased in Giza 168. Mycorrhization changed the polyamine balance under saline conditions, an increase in putrescine level associated with low contents of spermidine and spermine in Giza 168 was observed, while Sids 1 showed a decrease in putrescine and high increase in spermidine and spermine. Moreover, mycorrhizal inoculation significantly reduced the activities of diamine oxidase and polyamine oxidase in salt-stressed wheat plants. Modulation of nutrient acquisition and polyamine pool can be one of the mechanisms used by AMF to improve wheat adaptation to saline soils. This is the first report dealing with mycorrhization effect on diamine oxidase and polyamine oxidase activities under salt stress.     

Comparative performance of δ13C,ion accumulation and agronomic parameters for phenotyping durum wheat genotypes under various irrigation water salinities

The use of efficient selection traits for screening under contrasting irrigation water salinity is a challenge for breeders. To identify patterns, grain yield (GY) and yield components (kernels m^?2, thousand kernels weight), growth traits (plant height, biomass), flag leaf ion accumulation (Na⁺ and K⁺), carbon isotope composition (δ¹³C_grain) and nitrogen concentration (N_grain) of grains were assessed on 25 durum wheat genotypes (G) in two consecutive growing seasons (2010 and 2011), in three semi‐arid locations in Tunisia. Each location differed in their irrigation water salinity as measured by electrical conductivity: Echbika (S1, 6 dS m^?1), Barrouta (S2, 12 dS m^?1) and Sidi Bouzid (S3, 18 dS m^?1). GY was shown to be negatively correlated to N_grain as well as to δ¹³C_grain. This is confirmed by a multiple linear regression analysis that showed that both δ¹³C_grain and N_grain were the major determinant components for GY variability under S3. A high genotypic variability was observed and the improved genotype Maali exhibited the most stable GY under the three irrigation water salinities and the two cropping seasons. Maali showed the lowest δ¹³C_grain. This indicates that tolerance in durum wheat is likely to be correlated to the ability of maintaining a high stomatal conductance. According to our data suggests δ¹³C_grain can be used for an efficient screening of salt tolerant durum wheat. Under our experimental conditions, N_grain was shown to be highly correlated to δ¹³C_grain and can therefore be easier‐to‐use trait to assess the tolerance to salinity.