The Effects of Saline Water Drip Irrigation on Tomato Yield,Quality, and Blossom-End Rot Incidence --- A 3a Case Study in the South of China

Saline water resources are abundant in the coastal areas of south China. Most of these resources still have not been effectively utilized. A 3-year study on the effects of saline water irrigation on tomato yield, quality and blossom-end rot (BER) was conducted at different lower limits of soil matric potential (-10 kPa, -20 kPa, -30 kPa, -40 kPa and -50 kPa). Saline water differing in electrical conductivity (EC) (3 dS/m, 4 dS/m, 4.5 dS/m, 5 dS/m and 5.5 dS/m) was supplied to the plant after the seedling establishment. In all three years, irrigation water with 5.5 dS/m salinity reduced the maximum leaf area index (LAI_m) and chlorophyll content the most significantly when compared with other salinity treatments. However, compared with the control treatment (CK), a slight increase in LAI_m and chlorophyll content was observed with 3~4 dS/m salinity. Saline water improved tomato quality, including fruit density, soluble solid, total acid, vitamin C and the sugar-acid ratio. There was a positive relationship between the overall tomato quality and salinity of irrigation water, as analyzed by principal component analysis (PCA). The tomato yield decreased with increased salinity. The 5.5 dS/m treatment reduced the tomato yield (Y_t) by 22.4~31.1%, 12.6~28.0% and 11.7~27.3%, respectively in 2012, 2013 and 2014, compared with CK. Moreover, a significant (P≤0.01) coupling effect of salinity and soil matric potential on Y_t was detected. Saline water caused Y_t to increase more markedly when the lower limit of soil matric potential was controlled at a relatively lower level. The critical salinity level that produced significant increases in the BER_i was 3 dS/m~4 dS/m. Following the increase in BER_i under saline water irrigation, marketable tomato yield (Y_m) decreased by 8.9%~33.8% in 2012, 5.1%~30.4% in 2013 and 10.1%~32.3% in 2014 compared with CK. In terms of maintaining the Y_t and Y_m, the salinity of irrigation water should be controlled under 4 dS/m, and the lower limit of soil matric potential should be greater than -20 kPa.     

Foliar and root absorption of Na+ and Cl− in maize and barley: Implications for salt tolerance screening and the use of saline sprinkler irrigation

Above-canopy sprinkler irrigation with saline water favours the absorption of salts by wetted leaves and this can cause a yield reduction additional to that which occurs in salt-affected soils. Outdoor pot experiments with both sprinkler and drip irrigation systems were conducted to determine foliar ion accumulation and performance of maize and barley plants exposed to four treatments: nonsaline control (C), salt applied only to the soil (S), salt applied only to the foliage (F) and salt applied to both the soil and to the foliage (F+S). The EC of the saline solution employed for maize in 1993 was 4.2 dS m^–1 (30 mM NaCl and 2.8 mM CaCl₂) and for barley in 1994, 9.6 dS m^–1 (47 mM NaCl and 23.5 mM CaCl₂). The soil surface of all pots was covered so that in the F treatment the soil was not salinized by the saline sprinkling and drip irrigation supplied nutrients in either fresh (treatments C and F) or saline water (treatments S and F+S).Saline sprinkling increased leaf sap Na⁺ concentrations much more than did soil salinity, especially in maize, even though the saline sprinkling was given only two or three times per week for 30 min, whereas the roots of plants grown in saline soil were continuously exposed to salinity. By contrast, leaf sap Cl^– concentrations were increased similarly by saline sprinkling and soil salinity in maize, and more by saline sprinkling than saline soil in barley. It is concluded that barley leaves, and to a greater extent maize leaves, lack the ability to selectively exclude Na⁺ when sprinkler irrigated with saline water. Moreover, maize leaves selectively absorbed Na⁺ over Cl^– whereas barley leaves showed no selectivity. When foliar and root absorption processes were operating together (F+S treatment) maize and barley leaves accumulated 11–14% less Na⁺ and Cl^– than the sum of individual absorption processes (treatment F plus treatment S) indicating a slight interaction between the absorption processes. Vegetative biomass at maturity and cumulative plant water use were significantly reduced by saline sprinkling. In maize, reductions in biomass and plant water use relative to the control were of similar magnitude for plants exposed only to saline sprinkling, or only to soil salinity; whereas in barley, saline sprinkling was more detrimental than was soil salinity. We suggest that crops that are salt tolerant because they possess root systems which efficiently restrict Na⁺ and Cl^– transport to the shoot, may not exhibit the same tolerance in sprinkler systems which wet the foliage with saline water. ei]T J Flowers     

Salinity-yield response functions of barley genotypes assessed with a triple line source sprinkler system

Evaluation of the salt tolerance of crop cultivars under field conditions is greatly complicated by the typical temporal and spatial variability of soil salinity. We obtained the grain yield – salinity response functions of 124 barley genotypes by growing them in ten salinity treatments imposed by a Triple Line Source Sprinkler (TLS) system during five consecutive years. Additional objectives were to ascertain the consistency and reproducibility over years of these functions, to quantify the deleterious effects of saline sprinkling irrigations, and to assess correlations between salinity tolerance and leaf sap salt concentration. The consistency and reproducibility of the response functions within and between years were adequate (only 8% of the response functions were discarded for statistical reasons). The Y _m (grain yield without salinity) and the EC₅₀ (the EC _e that reduces yield by 50%) estimates were not correlated (P > 0.05) suggesting that the most productive genotypes were not necessarily less salinity tolerant. Y _m was positively and significantly (P < 0.01) correlated with Y₆ and Y₁₂ (fitted grain yields at EC _e values of 6 dS m^-1, and 12 dS m^-1, respectively), indicating that it is a useful statistic in the selection of barley genotypes most productive under medium and high salinities. Foliar salt uptake due to saline sprinkling irrigations decreased the EC₅₀ by around 50% as compared with the salinity tolerance obtained with surface irrigation systems. No consistent relationships were found between either Y _m or EC₅₀ and the leaf sap osmotic potential, Cl, Ca, Na and K concentrations. They could not therefore be used in screening for salinity tolerance of barley. On the basis of the evidence from the present study, Y _m is the best statistic for predicting the most productive barley genotypes in salt-affected soils. This revised version was published online in June 2006 with corrections to the Cover Date.     

The response of potatoes (Solunum tuberosum L.) to salinity: plant growth and tuber yields in the arid desert of Israel

The response of potato cultivars to water salinity was studied under field conditions in sandy loessial soil in the arid desert of Southern Israel. The potatoes were drip-irrigated with water of three different salinities: water commonly used for irrigation (1.0–1.4 dS m^-1); saline water from a local well (6.1–6.9 dS m^-1); and a mixture of the two (3.84.3 dS m^-1). Salinity retarded plant emergence, enhanced haulm senescence and reduced growth of both haulms and tubers. Increasing the salinity progressively reduced tuber yields. Application of the saline water well after plant establishment (Expt A) decreased tuber yields by 615% and 22–31% in the intermediate and the high salinities, respectively. When irrigation with saline water was started soon after planting (Expt B), tuber yields were decreased by 0–17% and 21–79% in the intermediate and the high salinities, respectively. When the tubers emerged in salinised soil, tuber yields were decreased by 21–54% and 42–59% in the intermediate and the high salinities, respectively. A differential response of various cultivars to salinity was observed. None of the potato cultivars or clones exhibited exceptional tolerance to severe salinity. The earlier maturing cvs Atica and Désirée were the least susceptible to the moderate salinity imposed throughout the entire growing season; however, no association was noted between maturation time and the response to salinity.     

Water relations, nutrient content and developmental responses of Euonymus plants irrigated with water of different degrees of salinity and quality

For 20 weeks, the physiological responses of Euonymus japonica plants to different irrigation sources were studied. Four irrigation treatments were applied at 100 % water holding capacity: control (electrical conductivity (EC) <0.9 dS m^?1); irrigation water normally used in the area (irrigator’s water) IW (EC: 1.7 dS m^?1); NaCl solution, NaCl (EC: 4 dS m^?1); and wastewater, WW (EC: 4 dS m^?1). This was followed by a recovery period of 13 weeks, when all the plants were rewatered with the same amount and quality of irrigation water as the control plants. Despite the differences in the chemical properties of the water used, the plants irrigated with NaCl and WW showed similar alterations in growth and size compared with the control even at the end of the recovery period. Leaf number was affected even when the EC of the irrigation water was of 1.7 dS m^?1 (IW), indicating the salt sensitivity of this parameter. Stomatal conductance (g_s) and photosynthesis (P_n), as well as stem water potential (Ψ_stem), were most affected in plants irrigated with the most saline waters (NaCl and WW). At the end of the experiment the above parameters recovered, while IW plants showed similar values to the control. The higher Na⁺ and Cl⁺ uptake by NaCl and WW plants led them to show osmotic adjustment throughout the experiment. The highest amount of boron found in WW plants did not affect root growth. Wastewater can be used as a water management strategy for ornamental plant production, as long as the water quality is not too saline, since the negative effect of salt on the aesthetic value of plants need to be taken into consideration.     

Grafting influence on the weight and quality of tomato fruit under salt stress

Two commercial tomato cultivars were used to determine whether grafting could prevent decrease of fruit weight and quality under salt stress conditions. The cultivars Buran F1 and Berberana F1 were grafted onto rootstock ‘Maxifort’ and grown under three levels of elevated soil salinity (EC 3.80 dS m^?1, 6.95 dS m^?1 and 9.12 dS m^?1). Fruit weight reduction of grafted plants was lower (about 20–30%) in comparison with non‐grafted ones. Salt stress at the second salinity level (EC 6.95 dS m^?1) induced the highest alteration of examined growth and quality parameters. The total increase of phenols, flavonoids, ascorbate and lycopene content in the fruits of both grafted and non‐grafted plants for both cultivars had a similar trend and intensity, though some inter‐cultivar variation was observed. The possibility of grafting tomato plants to improve salt tolerance without fruit quality loss is discussed.     

Salt tolerance of eggplant

Summary No quantitative information is available regarding the salt tolerance of eggplant (Solanum melongena L.). The present study was conducted over a two-year period in small field plots irrigated by drip, where irrigation frequency was also a variable. The salt tolerance function may be described by the equation Y_r=100–6.9 (EC_e−1.1), where Y_r=relative yield of fruit, EC_e=the mean integrated electrical conductivity at the soil saturation extract, 1.1 dS/m=threshold salinity. Salt was distributed reasonably uniformly within the root zone.     

Getting to the roots of Cicer arietinum L. (chickpea) to study the effect of salinity on morpho-physiological,biochemical and molecular traits

The effect of saline irrigation (EC_iw 6 dS m^?1 and 9 dS m^?1) on the roots of Cicer arietinum L. genotypes was examined at morpho-physiological, biochemical and molecular levels. Reduction in root growth due to salinity was observed, but less effect was seen on the roots of genotypes KWR 108, ICCV 10, CSG 8962, and S7 as compared to the other genotypes. Cell turgor was maintained in tolerant genotypes through optimum water relations and osmoprotectants (proline and total soluble sugars) than the sensitive cultivars. Salinity caused oxidative stress as increased hydrogen peroxide and malondialdehyde were noticed, where low accumulation was observed in tolerant genotypes due to the higher activity of enzymatic antioxidants (superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase and peroxidase). Na⁺/K⁺ ratio increased, but more increment was reported in sensitive cultivars. Gene expression studies depicted that genes encoding pyrroline-5-carboxylate synthetase and pyrroline-5-carboxylate reductase got upregulated and that of proline dehydrogenase was downregulated and more fold change with respect to control was in the salt tolerant check CSG 8962 and the genotype KWR 108. Higher expression of the genes encoding reactive oxygen species scavenging enzymes namely, superoxide dismutase, catalase, peroxidase, and those involved in the ascorbate–glutathione cycle was noticed in KWR 108 and CSG 8962 than ICC 4463. Enhanced expression of sodium transporter HKT1 due to salinity can be correlated with ion homeostasis maintenance. Cumulative effects of osmolytes, enzymatic antioxidants and maintaining ion homeostasis in root enable chickpea plants to survive in saline environments.     

Salt tolerance of four tomato hybrids

Summary A greenhouse lysimeter experiment was conducted to evaluate the response of tomato hybrids to varying levels of salinity. Four tomato hybrids F-172, F-150, Bornia and Diego were grown at four salinity levels. The soil was salinized prior to transplanting by irrigating with waters that were prepared by adding NaCl to the tap water. The electrical conductivities of the irrigation waters were 1.8, 4.5, 7.0, and 9.5 dS/m at 25°C. Yield, fruit quality, and leaf mineral composition were measured. Fifty percent fruint yield reduction for all hybrids was associated with a soil salinity of 5.1 dS/m. Each unit increase in salinity above 2 dS/m reduced yield by 14%. This indicates that these tomato hybrids are more salt sensitive than the older varieties. Fruit quality and leaf mineral composition were also affected by salinity and hybrid.     

Effect of salinity on mycorrhizal onion and tomato in soil with and without additional phosphate

Summary Vesicular-arbuscular mycorrhizal fungi (VAM) are known to increase plant growth in saline soils. Previous studies, however, have not distinguished whether this growth response is due to enhanced P uptake or a direct mechanism of increased plant salt tolerance by VAM. In a glasshouse experiment onions (Allium cepa L.) were grown in sterilized, low-P sandy loam soil amended with 0, 0.8, 1.6 mmol P kg^–1 soil with and without mycorrhizal inoculum. Pots were irrigated with saline waters having conductivities of 1.0, 2.8, 4.3, and 5.9 dS m^–1. Onion colonized withGlomus deserticola (Trappe, Bloss, and Menge) increased growth from 394% to 100% over non-inoculated control plants when soil P was low ( 0.2 mmol kg^–1 NaHCO₃-extractable P) at soil saturation extract salinities from 1.1 dS m^–1 to 8.8 dS m^–1. When 0.8 and 1.6 mM P was added no dry weight differences due to VAM were observed, however, K and P concentrations were higher in VAM plants in saline treatments.Glomus fasciculatum (Gerdeman and Trappe) andGlomus mosseae (Nicol. and Gerd.) isolates increased growth of VAM tomato 44% to 193% in non-sterilized, saline soil (10 dS m^–1 saturation extract) despite having little effect on growth in less saline conditions when soil P was low. Higher tomato water potentials, along with improved K nutrition by VAM in onion, indicate mechanisms other than increased P nutrition may be important for VAM plants growing under saline stress. These effects appear to be secondary to the effects of VAM on P uptake.     

Life-history parameters of the western flower thrips,Frankliniella occidentalis,are affected by host plant salinity stress

Salinization, as one of the foremost abiotic stresses, is an intensifying problem in many agroecosystems. Climatic changes, along with altering land use and also salinity of irrigation water all lead to enhanced soil salinity in agricultural lands. Changes in plant characteristics, as a result of raising soil salinity, may impose bottom-up impact on plant-feeding insects. We assessed the bottom-up impact of salinity stress on demographic traits of the western flower thrips (WFT), Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), on cherry tomato, Solanum lycopersicum L. var. cerasiforme (Solanaceae) plants under greenhouse conditions (27 ± 2 °C, 65 ± 5% r.h., and L16:D8 photoperiod). Our results indicated that salinity stress interfered with the immature development period, adult longevity, and sex ratio of WFT. Salinity stress biased the sex ratio in favor of males. Significant concentration-dependent differences were observed in the intrinsic (r) and finite (λ) increase rates and the net reproduction rate (R₀) of WFT at different salinity levels. Salinity adversely influenced WFT development; nonetheless, population projection forecasted an ascending WFT population growth under moderate salinity stress of 100 mM (2.8 dS m⁻¹ of NaCl), whereas severe salinity stress of 150 mM (4.7 dS m⁻¹ of NaCl) resulted in remarkable fitness costs in WFT. This study demonstrates that WFT has the potential to become problematic in regions with moderate salinity. Therefore, it might exacerbate the detrimental impact of salinity on tomato production. The current survey provides information on the abundance of WFT on saline-stressed tomato plants, thereby contributing to developing environmentally friendly measures to manage this notorious species in ecosystems under salinity stress.     

Improved Tolerance of <Emphasis Type="Italic">Acacia nilotica</Emphasis> to Salt Stress by Arbuscular Mycorrhiza, <Emphasis Type="Italic">Glomus fasciculatum</Emphasis> may be Partly Related to Elevated K/Na Ratios in Root and Shoot Tissues

A pot experiment was conducted to examine the effect of arbuscular mycorrhizal fungus, Glomus fasciculatum, and salinity on the growth of Acacia nilotica. Plants were grown in soil under different salinity levels (1.2, 4.0, 6.5, and 9.5 dS m⁻¹). In saline soil, mycorrhizal colonization was higher at 1.2, 4.0, and 6.5 dS m⁻¹ salinity levels in AM-inoculated plants, which decreased as salinity levels further increased (9.5 dS m⁻¹). Mycorrhizal plants maintained greater root and shoot biomass at all salinity levels compared to nonmycorrhizal plants. AM-inoculated plants had higher P, Zn, and Cu concentrations than uninoculated plants. In mycorrhizal plants, nutrient concentrations decreased with the increasing levels of salinity, but were higher than those of the nonmycorrhizal plants. Mycorrhizal plants had greater Na concentration at low salinity levels (1.2, 4.0 dS m⁻¹), which lowered as salinity levels increased (6.5, 9.5 dS m⁻¹), whereas Na concentration increased in control plants. Mycorrhizal plants accumulated a higher concentration of K at all salinity levels. Unlike Na, the uptake of K increased in shoot tissues of mycorrhizal plants with the increasing levels of salinity. Our results indicate that mycorrhizal fungus alleviates deleterious effects of saline soils on plant growth that could be primarily related to improved P nutrition. The improved K/Na ratios in root and shoot tissues of mycorrhizal plants may help in protecting disruption of K-mediated enzymatic processes under salt stress conditions.     

Effect of salinity and inoculation on growth,nitrogen fixation and nutrient uptake ofVigna radiata (L.) Wilczek

This study reports the effect of salinity and inoculation on growth, ion uptake and nitrogen fixation byVigna radiata. A soil EC_e level of 7.5 dS m⁻¹ was quite detrimental causing about 60% decline in dry matter and grain yield of mungbean plants whereas a soil EC_e level of 10.0 dS m⁻¹ was almost toxic. In contrast most of the studied strains of Rhizobium were salt tolerant. Nevertheless, nodulation, nitrogen fixation and total nitrogen concentration in the plant was drastically affected at high salt concentration. A noticeable decline in acetylene reduction activity occurred when salinity level increased to 7.5 dS m⁻¹.     

Simulation Models of Leaf Area Index and Yield for Cotton Grown with Different Soil Conditioners

Simulation models of leaf area index (LAI) and yield for cotton can provide a theoretical foundation for predicting future variations in yield. This paper analyses the increase in LAI and the relationships between LAI, dry matter, and yield for cotton under three soil conditioners near Korla, Xinjiang, China. Dynamic changes in cotton LAI were evaluated using modified logistic, Gaussian, modified Gaussian, log normal, and cubic polynomial models. Universal models for simulating the relative leaf area index (RLAI) were established in which the application rate of soil conditioner was used to estimate the maximum LAI (LAI _m). In addition, the relationships between LAI _m and dry matter mass, yield, and the harvest index were investigated, and a simulation model for yield is proposed. A feasibility analysis of the models indicated that the cubic polynomial and Gaussian models were less accurate than the other three models for simulating increases in RLAI. Despite significant differences in LAIs under the type and amount of soil conditioner applied, LAI _m could be described by aboveground dry matter using Michaelis-Menten kinetics. Moreover, the simulation model for cotton yield based on LAI _m and the harvest index presented in this work provided important theoretical insights for improving water use efficiency in cotton cultivation and for identifying optimal application rates of soil conditioners.     

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.     

Effects of residual soil salinity resulting from irrigation with sulphate waters on lettuce

Summary The response of lettuce (Lactuca sativa L.) to residual soil salinity as influenced by the ionic composition of two different saline waters (EC_w=3.1 dS/m, referenced at 25°C) and rain water, was investigated in a greenhouse experiment with three successive plantings of lettuce in the same soil. One of the saline waters was saturated with gypsum (SO₄=35 mol (−)m⁻³) and the other contained SO₄ at 15 mol (−)m⁻³ and Na and Cl at 18 and 14 mol (±)m⁻³, respectively (mixed water). All waters were applied with a 0.3 leaching fraction. Soil water salinity and sodium adsorption ratio (SAR) increased in both cases using saline waters. The effect of mixed saline water was higher and became more marked after each planting, resulting from higher contribution of Na and Cl to soil salinity. With both saline waters, soil solution became saturated with gypsum. At first planting, gypsum saturated and mixed waters produced fresh yield increases of 15 and 24%, respectively, relative to rain water. At second planting, however, there was reduction in yield of 11 and 22%, respectively, relative to rain water; at third planting yield reduced by 22 and 76% with gypsum saturated and mixed water, respectively.     

Response of Alfalfa Genotypes to Saline Water Irrigation

The influence of saline water (4, 8, 12 dS m^–1) irrigation on gas exchange and growth response of alfalfa genotypes Anand-2, T-9 and IL-112 was studied. T-9 and IL-112 showed a significant increase in net photosynthetic rate (P_N) at low salinity (4 dS m^–1) compared to the control whereas Anand-2 maintained an unaltered P_N. Reduction in P_N at higher salinities was primarily due to reduction of stomatal conductance. There was a greater reduction in transpiration rate as compared to P_N rate, which resulted in an increase in water use efficiency (WUE). High WUE may serve as one of the strategies of the plant to withstand saline environment. However, the slight increase in WUE in Anand-2 could not help in maintaining its growth. Increase in Na⁺ concentration in comparison to K⁺ concentration may also contribute to the inhibition in growth.     

Effect of salinity on growth,water use and nutrient use in radish (Raphanus sativus L.)

Radish (Raphanus sativus L.) plants were grown at five soil salinity levels (1, 2, 4, 9 and 13 dS m^-1) to analyse the effects on growth, dry matter partitioning, leaf expansion and water and nutrient use. Salinity was varied by proportionally changing the concentration of all macro nutrients. When the electrical conductivity (EC) of the soil solution increased from 1 to 13 dS m^-1, the influx concentration of the nutrients absorbed by the plants (the ratio between the uptakes of nutrients and water) increased only from 1.6 to 3.5 dS m^-1. The total nutrient uptake showed an optimum at an EC of the soil solution of about 4 dS m^-1. The data suggest that at low salinity level (≤ 2 dS m^-1) the nutrient uptake was limited by availability while at high salinity (>4 dS m^-1) it was limited by the growth of the plant. Total water use by the plants decreased and water use efficiency increased at high salinity. Plant growth was optimal at 2–4 dS m^-1. At salinities higher than 4 dS m^-1 total plant dry weight decreased 2.8% per dS m^-1. About 80% of the growth reduction at high salinity could be attributed to reduction of leaf area expansion and hence to reduction of light interception. The remaining 20% of the salinity effect on growth was most likely explained by a decrease in stomatal conductance. The small leaf area at high salinity was related to a reduced specific leaf area and increased tuber/shoot weight ratio. The latter could be attributed to tuber formation starting at a smaller plant size at high salinity. This revised version was published online in June 2006 with corrections to the Cover Date.     

Comparison of Distichlis spicata and Suaeda aegyptiaca in response to water salinity: Candidate halophytic species for saline soils remediation

Distichlis spicata and Suaeda aegyptiaca are two potential halophytic plant species for bioremediation of salt degraded soils, and development of saline agriculture. The physiological responses of the species to different levels of salinity (EC 0, 12, 24, 36, and 48 dS/m) in a controlled environment experiment were studied. Both species showed a high level of tolerance to elevated concentrations of salt in the irrigation water. The shoot fresh and dry weights in S. aegyptiaca increased till 36 dS/m and were sustained under 48 dS/m while in D. spicata, both parameters decreased as salinity increased. Glycine betaine accumulation did not change in D. spicata with increasing salinity, whereas proline content revealed a marked increase of 7.13 fold in 48 dS/m salinity compared to the control, which showed its critical osmoprotection role in the plant. In S. aegyptiaca, both osmolytes content significantly increased at high salinity levels (36 and 48 dS/m) up to 3.22 and 2.0 folds, respectively. Overall, S. aegyptiaca had a better potential of Na⁺ phytoremediation, and tolerated higher salinity compared to D. spicata. In contrast, the vigorous root and rhizome growth in D. spicata made it a proper solution for protecting the soils against further erosion under saline conditions.     

The Influence Of Salinity On Verticillium dahliae In Stem Cuttings Of Five Olive Cultivars

Verticillium dahliae represents one of the main limiting factors in olive production in the Mediterranean countries. Increasing shortage of fresh water and land, increase the pressure on using alternative sources of marginal or saline water, and land previously cropped with V. dahliae host plants. The objective of the present study was to evaluate the influence of salinity on V. dahliae expression in olive stem cuttings. V. dahliae‐inoculated cuttings of cvs. Picual, Frantoio, Mansanillo and Barnea, showed higher senescence symptoms than their non‐inoculated controls. Colonization levels obtained in cv. Picual were significantly higher than in cv. Frantoio. Manzanillo was the most sensitive cultivar to salinity alone, with significant senescence symptoms in 4 and 6 dS/m NaCl treatments. When cv. Manzanillo was exposed to both salinity and V. dahliae, significantly higher senescence symptoms were obtained as compared with each of them separately. Senescence symptoms of cv. Picual exposed to V. dahliae, whether or not in combination with saline solutions, were significantly higher than those when cuttings were exposed to a saline solution alone. In cv. Frantoio, which is more resistant to salinity than the other cultivars, significantly high senescence symptoms were observed only in combination of V. dahliae and high saline concentration (8 dS/m). The fungal colonization index in cv. Manzanillo in high salinity (8 dS/m) was significantly higher than in the treatment without salt. In cv. Barnea, colonization index in 8 dS/m salinity was significantly higher than in the 4 dS/m concentration or control (fresh water). In conclusion, our findings demonstrate the interaction between V. dahliae and saline irrigation in various cultivars. Thus, stem cuttings could serve as an effective screening method in breeding olive clones for V. dahliae resistance, salt tolerance and their interaction.