<i>Azospirillum brasilense</i> and <i>Saccharomyces cerevisiae</i> as Alternative for Decrease the Effect of Salinity Stress in Tomato (<i>Lycopersicon esculentum</i>) Growth

The salinity stress is one of the most relevant abiotic stresses that affects the agricultural production. The present study was performed to study the improvement of the salt tolerance of tomato plants which is known for their susceptibility to salt stress. The present study aimed to assess to what extent strain Azospirillum brasilense (N040) and Saccharomyces cerevisiae improve the salt tolerance to tomato plants treated with different salt concentration. The inoculant strain A. brasilense (N040) was previously adapted to survive up to 7% NaCl in the basal media. A greenhouse experiment was conducted to evaluate the effect of this inoculation on growth parameter such as: plant height, root length, fresh and dry weight, fruits fresh weight, chlorophyll content, proline and total soluble sugar in tomato plants under salt stress condition. The results revealed that co-inoculation of Azospirillum brasilense (N040) and Saccharomyces cerevisiae significantly increased the level of proline (8.63 mg/g FW) and total soluble sugar (120 mg/g FW) of leaves under salinity condition comparing to non-inoculated plants (2.3 mg/g FW and 70 mg/g FW, respectively). Plants co-inoculated with adapted strain of A. brasilense and S. cerevisiae showed the highest significant (p < 0.01) increase in fruit yield (1166.6 g/plant), plant high (115 cm) and roots length (52.6) compared whit un-inoculated control plants (42 g/pant, 43.3 cm and 29.6 cm, respectively). In contrast, Na⁺ ion content was significantly decreased in the leaves of salt stressed plants treated with the A. brasilense (N040) and S. cerevisiae. Finally, the results showed that dual benefits provided by both A. brasilense (N040) and S. cerevisiae can provide a major way to improve tomato yields in saline soils.     

Impact of the microalga Dunaliella salina (Dunal) Teodoresco culture and its β-carotene extract on the development of salt-stressed squash (Cucurbita pepo L. cv. Mabrouka)

Salinity is a major threat to crop production and global food security. Algae and their extracts containing bioactive compounds can enhance the salt tolerance of plants, including the salt-sensitive plants. The current study evaluated the efficacy of Dunaliella salina (Dunal) Teodoresco culture and/or its β-carotene extract in improving the salt tolerance of squash (Cucurbita pepo L. cv. Mabrouka). Amendment of C. pepo with D. salina culture and/or its β-carotene extract was more effective in alleviating the impact of moderate salinity imposed by seawater dilution of 2.5 dS m⁻¹ than either low (0.55 dS m⁻¹) or high (3.5 dS m⁻¹) salinity, with a comparable effect to that of salicylic acid (SA). Plants that received a combination of D. salina culture and its β-carotene extract showed significantly higher growth (total biomass, fruit productivity) and physiological attributes (photosynthetic pigments, nitrogen (N), phosphorus (P), and potassium (K⁺) contents) than those receiving either amendment alone, reaching up to 80–90% of the SA-treated plants at moderate salinity (2.5 dS m⁻¹). The combination could enhance the antioxidant activity of moderately salt-stressed C. pepo via increasing carotenoids and phenolics contents, suggesting that this combination could enhance the adaptation of C. pepo to the moderate salinity. The present study recommends using the blooms of D. salina and its β-carotene that is naturally secreted in situ in natural or synthetic open systems in improving the salt tolerance of C. pepo instead of using the expensive synthetic hormones.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12298-022-01176-6.     

Microalgal biotechnology: Carotenoid and glycerol production by the green algae <Emphasis Type="Italic">Dunaliella</Emphasis> isolated from the Gave-Khooni salt marsh,Iran

In this study, carotenoid and glycerol production in two unicellular green algae (Dunaliella salina and D. viridis) isolated from the Gave-Khooni salt marsh grown in media containing five different salt concentrations (0.17, 1, 2, 3, and 4 M NaCl) were evaluated under sterile conditions. Algae growth decreased as the medium salinity increased. Optimum growth of D. salina and D. viridis were obtained at 2 and 1 M NaCl, respectively. As salinity increased, glycerol and carotenoid production were increased in D. salina, whereas lower values for these products were produced in D. viridis under the same conditions. Furthermore, the cell color of D. salina changed from green to orange-red following accumulation of carotenoid, but the color of D. viridis was not changed. Thereby, it seems that the Iranian D. salina may be suitable for carotenoid production (betacarotene) on a large scale. In addition, since carotenoid compounds enhance the efficiency of photosynthesis and glycerol synthesis, it appears that the pathway for glycerol production and mechanisms of salt tolerance in D. viridis are unique from those of D. salina.     

The mass culture of Dunaliella viridis (Volvocales,Chlorophyta) for oxygenated carotenoids : laboratory and pilot plant studies

The biology, and hence the mass culture, of Dunaliella viridis closely follows that of Dunaliella salina, which is successfully mass cultured for the production of -carotene. Both algae can grow at extremely high salinities and light intensities. They co-exist in the coastal salt lake, Hutt Lagoon, Western Australia. In contrast to D. salina, D. viridis does not accumulate large amounts of -carotene, producing only up to 0.7% of mixed carotenoids (lutein, zeaxathin, other oxygenated carotenoids and -carotene), compared to D. salina's ca 10% dry wt of mainly -carotene. However, in laboratory experiments, D. viridisgrew much faster and to much higher cell densities than D. salina, and attained levels of mixed carotenoids similar to those of D. salina (ca 13 mg L^–1 carotenoid). Preliminary experiments in outdoor ponds were much less promising. Harvesting by chemical flocculation was as effective as with D. salina, but extraction of carotenoids directly into vegetable oil proved inefficient. When incorporated into feed, caretonoids derived from D. viridis pigmented hen eggs acceptably. Extrapolating from laboratory results, and using costing derived from D. salina technology, the cost of production of mixed oxygenated carotenoids from D. viridis was similar to that for the production of -carotene from D. salina, at ca $A500 kg^–1.     

Genome-Wide Identification of Candidate Genes Associated with <i>β</i>-glucan Traits in a Hulled and Hulless Barley (<i>Hordeum vulgare</i> L.) Population

Barley grain is a valuable source of β-glucan, which is an important component of dietary fiber with significant human health benefits. Although the genetic basis of β-glucan biosynthesis has been widely studied, a genome-wide association study (GWAS) is still required for a scan of the candidate genes related to the complex quantitative trait based on the high-quality barley reference genome. In this study, a GWAS was conducted using a population composed of 87 barley landraces (39 hulled and 48 hulless, β-glucan from 2.07% to 6.56%) with 191,098 nucleotide polymorphisms (SNPs) markers to cover the chromosomes with the highest density. The population was divided into four sub-populations (POP1~POP4), and the β-glucan content in POP2 was significantly higher than that in other groups, in which most of the hulless barley landraces are from Qinghai-Tibet Plateau in China. Among seven SNP markers identified by GWAS, two (SNP2 and SNP3) of them showed positive correlation to β-glucan trait and the remaining five (SNP1, SNP4, SNP5, SNP6 and SNP7) showed the negative relationship. Two candidate genes linked to SNP7, HORVU7Hr1G000320 and HORVU7Hr1G000040, belong to the nucleotide triphosphate hydrolase superfamily which is probable to affect the activities of β-glucan synthase. Another candidate gene associated with SNP1, HORVU1Hr1G000010, is possibly involved in sugar response. In conclusion, our results provide new insights into the genetic basis of β-glucan accumulation in barley grains, and the discovery of new SNP markers distributed in each chromosome and the associated candidate genes will be valuable for the breeding of functional barley varieties with high β-glucan.     

Differential Responses of <i>NHX1</i> and <i>SOS1</i> Gene Expressions to Salinity in two <i>Miscanthus sinensis</i> Anderss. Accessions with Different Salt Tolerance

The lignocellulosic crop Miscanthus spp. has been identified as a good candidate for biomass production. The responses of Miscanthus sinensis Anderss. to salinity were studied to satisfy the needs for high yields in marginal areas and to avoid competition with food production. The results indicated that the relative advantages of the tolerant accession over the sensitive one under saline conditions were associated with restricted Na⁺ accumulation in shoots. Seedlings of two accessions (salt-tolerant ‘JM0119’ and salt-sensitive ‘JM0099’) were subjected to 0 (control), 100, 200, and 300 mM NaCl stress to better understand the salt-induced biochemical responses of genes involved in Na⁺ accumulation in M. sinensis. The adaptation responses of genes encoding for Na⁺ /H⁺ antiporters, NHX1 and SOS1 to NaCl stress were examined in JM0119 and JM0099.The cDNA sequences of genes examined were highly conserved among the relatives of M. sinensis based on the sequencing on approximate 600 bp-long cDNA fragments obtained from degenerate PCR. These salt-induced variations of gene expression investigated by quantitative real-time PCR provided evidences for insights of the molecular mechanisms of salt tolerance in M. sinensis. The expression of NHX1 was up-regulated by salt stress in JM0119 shoot and root tissues. However, it was hardly affected in JM0099 shoot tissue except for a significant increase at the 100 mM salt treatment, and it was salt-suppressed in the JM0099 root tissue. In the root tissue, the expression of SOS1 was induced by the high salt treatment in JM0119 but repressed by all salt treatments in JM0099. Thus, the remarkably higher expression of NHX1 and SOS1 were associated with the resistance to Na⁺ toxicity by regulation of the Na⁺ influx, efflux, and sequestration under different salt conditions.     

Influence of stress factors on growth and pigment production in three Dunaliella species cultivated outdoors in flat-plate photobioreactors

Abstract

Growth and production of carotenoid in three Dunaliella species (Dunaliella salina (Dunal) Teodoresco, Dunaliella bardawil Ben-Amotz & Avron and Dunaliella sp.) were investigated using flat-plate photobioreactors in outdoor conditions with two optical paths (3?cm and 5?cm). The experiment was conducted in duplicate and lasted four weeks during which light intensity, temperature, pH and optical density were checked daily. The pigment production (total carotenoid and chlorophyll a) was monitored every two days. To induce an additional stress besides temperature and light intensity, two different salt concentrations were used, i.e. 6% and 8% NaCl. The highest growth in all treatment groups was noticed for Dunaliella sp. followed by D. bardawil and D. salina. D. salina produced a higher content of carotenoid concentrations corresponding to 5?cm/8% and 5?cm/6% groups; 779.102?±?0.434?μg.mL^?1 and 694.326?±?0.098?μg.mL^?1 were registered at the end of the experiment. The same species had also greater content of β-carotene.     

Predictive modeling of β-carotene accumulation by Dunaliella salina as a function of pH,NaCI, and irradiance

Predictive modeling of β-carotene accumulation by Dunaliella salina as a function of NaCI, pH, and irradiance was studied. Modified Logistic, Gompertz, Schnute, Richards, and Stannard models were fitted to describe β-carotene accumulation by the alga under various environmental conditions. Lag time (λ, days), maximum accumulation (A, pg/cell), and the maximum production rate (μ, 1/day) for β-carotene accumulation were calculated by modified Logistic and Gompertz models. Values of λ, A, and μ for β-carotene accumulation varied between 0.26 and 20.14 days, 57.48 to 198.76 pg β-carotene/cell, and 1.80 to 3.68 1/day, respectively. Results revealed that Logistic and Gompertz models could be used to describe the accumulation of β-carotene by D. salina as a function of salt concentrations, pH, and irradiance. The highest asymptotic value was predicted from Logistic and Gompertz models at pH 9.0, 48 kerg/(cm² s) light intensity, and 20% NaCl concentration.     

ACCUMULATION OF β-CAROTENE IN HALOTOLERANT ALGE: PURIFICATION AND CHARACTERIZATION OF β-CAROTENE-RICH GLOBULES FROM DUNALIELLA BARDAWIL (CHLOROPHYCEAE)1

Dunaliella bardawil Ben-Amotz & Avron, but not most other Dunaliella species, has a unique property of being able to accumulate, in addition to glycerol, large amounts of β-carotene when cultivated under appropriate conditions. These include high light intensity, a high sodium chloride concentration, nitrate deficiency and extreme temperatures. Under conditions of maximal carotene accumulation D. bardawil contains at least 8% of its dry weight as β-carotene while D. salina grown under similar conditions contains only about 0.3%. Electron micrographs of D. bardawil grown under conditions of high β-carotene accumulation show many β-carotene containing globules located in the interthylakoid spaces of the chloroplast. The same algae grown under conditions where β-carotene does not accumulate, contain few to no β-carotene globules. The β-carotene-rich globules were released from the algae into an aqueous medium by a two-stage osmotic shock technique and further purified by centrifugal ion on 10% sucrose. The isolated purified globules were shown by electron microscopy to be free of significant contamination and composed of membrane-free osmiophilic droplets with an average diameter of 150 nm. Reversed phase high performance liquid chromatography of a total pigment extract of the cells revealed the presence of β-carotene as the major pigment, together with chlorophylls a and b, α-carotene and the xanthophylls lutein, neoxauthin and zeaxanthin. β-Carotene accounted for essentially all the pigment in the purified globules. Analysis of the algal and globule β-carotene fractions by HPLC showed that the β-carotene was composed of approximately equal amounts of all-trans β-carotene and of its 9-cis isomer. Intact D. bardawil cells contained on a dry weight basis about 30% glycerol, 30% protein, 18% lipid, 11% carbohydrate, 9%β-carotene and 1% chlorophyll. The β-carotene globules were composed of practically only neutral lipids, more than half of which was β-carotene. It is suggested that the β-carotene globules may serve to protect D. bardawil against injury by the high intensity irradiation to which this alga is usually exposed in nature.     

Physiological and Biochemical Characteristics and Response Patterns of Salinity Stress Responsive Genes (SSRGs) in Wild Quinoa (<i>Chenopodium quinoa</i> L.)

Cultivating salt-tolerant crops is a feasible way to effectively utilize saline-alkali land and solve the problem of underutilization of saline soils. Quinoa, a protein-comprehensive cereal in the plant kingdom, is an exceptional crop in terms of salt stress tolerance level. It seems an excellent model for the exploration of salt-tolerance mechanisms and cultivation of salt-tolerant germplasms. In this study, the seeds and seedlings of the quinoa cultivar Shelly were treated with different concentrations of NaCl solution. The physiological, biochemical characteristics and agronomic traits were investigated, and the response patterns of three salt stress-responsive genes (SSRGs) in quinoa were determined by real-time PCR. The optimum level of stress tolerance of quinoa cultivar Shelly was found in the range of 250–350 mM concentration of NaCl. Salt stress significantly induced expression of superoxide dismutase (SOD), peroxidase (POD), and particularly betaine aldehyde dehydrogenase (BADH). BADH was discovered to be more sensitive to salt stress and played an important role in the salt stress tolerance of quinoa seedlings, particularly at high NaCl concentrations, as it displayed upregulation until 24 h under 100 mM salt treatment. Moreover, it showed upregulation until 12 h under 250 mM salt stress. Taken together, these results suggest that BADH played an essential role in the salt-tolerance mechanism of quinoa. Based on the expression level and prompt response induced by NaCl, we suggest that the BADH can be considered as a molecular marker for screening salt-tolerant quinoa germplasm at the early stages of crop development. Salt treatment at different plant ontogeny or at different concentrations had a significant impact on quinoa growth. Therefore, an appropriate treatment approach needs to be chosen rationally in the process of screening salt-tolerant quinoa germplasm, which is useful to the utilization of saline soils. Our study provides a fundamental information to deepen knowledge of the salt tolerance mechanism of quinoa for the development of salt-tolerant germplasm in crop breeding programs.     

不同盐度胁迫下杜氏盐藻全转录组测序及注释

【目的】通过对杜氏盐藻的转录组进行测序和基因功能分析,阐明不同浓度盐胁迫对杜氏盐藻生长发育以及不同信号途径的影响。【方法】分别获取9%NaCl浓度和24%NaCl浓度培养下的杜氏盐藻转录组并通过Illumina平台进行测序。将所得的序列进行拼接、去冗余处理。【结果】获得40682个unigenes,其中注释到NR数据库的10905个,注释到NT数据库的2768个,注释到SWISS-PROT数据库的7261个,注释到COG/KOG数据库的6499个。受到高盐胁迫的杜氏盐藻细胞相比低盐环境下,有717个基因表达上调,1012个基因表达下调。进一步对60个显著差异基因进行了功能聚类,发现盐胁迫诱导了光合作用途径的基因表达。【结论】杜氏盐藻通过提高光合作用基因表达增强耐盐性。该研究最大范围上挖掘了杜氏盐藻在高盐和低盐环境的基因转录水平,为深入揭示杜氏盐藻盐胁迫下基因差异表达提供了平台,并为进一步研究杜氏盐藻耐盐机理提供理论依据。     

短小芽孢杆菌对盐藻SZ-05的生物量和β-胡萝卜素产量的影响

研究了短小芽孢杆菌（Bacillus pumilus）对盐藻空间诱变株系SZ-05（Dunaliella salina SZ-05）的生物量及β-胡萝卜素积累的影响。结果表明,短小芽孢杆菌显著提高了盐藻SZ-05的生物量和β-胡萝卜素的产量,明显降低了培养体系中的溶解氧和胞外多糖的含量。溶解氧的减少,使得藻细胞的光呼吸作用下降,光合作用速率提高,使藻细胞生物量增加。胞外多糖具有抗氧化作用,胞外多糖的减少可能进一步增加了β-胡萝卜素的合成,从而使β-胡萝卜素在胁迫条件下大幅度增加。     

On the Factors Which Determine Massive beta-Carotene Accumulation in the Halotolerant Alga Dunaliella bardawil

Dunaliella bardawil, a β-carotene-accumulating halotolerant alga, has been analyzed for the effect of various growth conditions on its pigment content, and compared with Dunaliella salina, a β-carotene nonaccumulating species. In D. bardawil, increasing light intensity and light period or inhibiting growth by various stress conditions such as nutrient deficiency or high salt concentration caused a decrease in the content of chlorophyll per cell and an increase in the amount of β-carotene per cell. As a result, the β-carotene-to-chlorophyll ratio increased from about 0.4 to 13 grams per gram and the alga changed its visual appearance from green to deep orange. D. salina grown similarly decreased in content of both chlorophyll and β-carotene per cell and the culture turned from green to yellowish. Low chlorophyll-containing cells of D. bardawil or D. salina exhibit very high photosynthetic rates when expressed on a chlorophyll basis (~600 micromoles O₂ evolved per milligram chlorophyll per hour).

Variation of pigment content in D. bardawil by a large variety of environmental agents has been correlated with the integral irradiance received by the algal culture during a division cycle. The higher the integral irradiance per division cycle, the lower the chlorophyll content per cell; the higher the β-carotene content per cell, and therefore the higher the β-carotene-to-chlorophyll ratio. The results are interpreted as indicating a protecting effect of β-carotene against injury by high irradiance under conditions of impairment in chlorophyll content per cell.

     

Effects of various mixed salt-alkaline stresses on growth,photosynthesis, and photosynthetic pigment concentrations of <Emphasis Type="Italic">Medicago ruthenica</Emphasis> seedlings

Soil salinization and alkalinization frequently co-occur in naturally saline and alkaline soils. To understand the characteristics of mixed salt-alkali stress and adaptive response of Medicago ruthenica seedlings to salt-alkali stress, water content of shoots, growth and photosynthetic characteristics of seedlings under 30 salt-alkaline combinations (salinity 24–120 mM and pH 7.03–10.32) with mixed salts (NaCl, Na₂SO₄, NaHCO₃, and Na₂CO₃) were examined. The indices were significantly affected by both salinity and pH. The interactive effects between salt and alkali stresses were significant, except for photosynthetic pigments. Water content of shoots, relative growth rates of shoots and roots and pigment concentrations showed decreasing trends with increasing salinity and alkalinity. The root activity under high alkalinity and salinity treatments gradually decreased, but was stimulated by the combined effects of low alkalinity and salinity. The survival rate decreased with increased salinity, except at pH 7.03–7.26 when all plants survived. Net photosynthetic rate, stomatal conductance and intercellular CO₂ concentration decreased with increased salinity and pH. M. ruthenica tolerated the stress of high salt concentration when alkali concentration was low, and the synergistic effects of high alkali and high salt concentrations lead to the death of some or all seedlings. M. ruthenica appeared to be saltalkali tolerant. Reducing the salt concentration or pH based on the salt components in the soil may be helpful to abate damage from mixed salt-alkaline stress.