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Diabetes is a chronic metabolic disease that creates high blood sugar level. Therefore, diabetes awareness is necessary to prevent diabetes by reducing sugar intake and using low-calorie alternative sweeteners instead. Stevia rebaudiana is a medicinal plant species belonging to the Compositae family. It is a sweet herb that contains diterpene glycosides, which are directly responsible for the sweet taste, but they have no caloric value. Since ancient times, there have been several reports on the use of S. rebaudiana as an alternative sweetener and extended research has been conducted on its phytochemicals and biological activities. The plant contains a good number of phytochemicals with significant biological activities, namely polyphenolic derivatives, diterpenes glycosides, alkaloids, glycosides, tannins, chlorophylls, carotenoids, etc. For industrial use, those phytochemicals could be extracted from the selected plant and used for the preparation of nutraceuticals and food additives. S. rebaudiana is a natural herb; therefore, it has fewer or minimal adverse effects on human health. The selected plant in various forms is used for the treatment of diabetes, colon cancer, obesity, cavities, and others. However, the literature review shows that the information on this plant and its uses is not systematic. The purpose of the present review is to explore the status of phytochemicals and biological activities of the selected plant for young researchers. Therefore, the updated data will help them to develop new nutraceuticals and food additives that could help in the production of pharmaceuticals to treat different ailments.

Aims The present study aimed to specifically transform stevioside (ST) into rubusoside (RS) through bioconversion with high efficiency, seeking to endow steviol glycosides (SGs) with subtle flavours for commercial acceptability. Methods and Results An endophytic bacterium named Lelliottia LST-1 was screened and confirmed to specifically convert ST into RS, reaching a conversion rate of 75.4% after response surface optimization. Phylogenetic analysis combined with complete genome sequencing demonstrated that LST-1 was also presumed to be a new species. To further explore the principle and process of biological transformation, the potential beta-glucosidases GH3-1, GH3-2, GH3-3 and GH3-4 were expressed, purified and reacted with SGs. High-performance liquid chromatography revealed that all enzymes hydrolysed ST and generated RS, but substrate specificity analysis indicated that GH3-2 had the highest substrate specificity towards STs and the highest enzyme activity. Conclusion The potential β-glucosidase GH3-2 in Lelliottia sp. LST-1 was found to specifically and efficiently convert ST to RS. Significance and Impact of Study The efficient biotransformation of ST into RS will be beneficial to its large-scale production and extensive application in the food and pharmaceutical industries.

Stevia rebaudiana is a sweet herbaceous perennial plant, which is frequently used in the preparation of plant‐based sweeteners. The demand for such sweeteners continues to increase due to purposeful nutrition and modern‐day metabolic syndromes. More than 20 types of steviol glycosides provide a sweet taste, which are more than 300 times sweeter than sucrose. They are formed of two main components, namely stevioside and rebaudioside A. Only a handful of studies have dealt with Stevia rebaudiana leaf extracts, the conversion of pure stevioside into the preferred rebaudioside A is more common. The aim of this study was to enrich the rebaudioside A content of Stevia rebaudiana leaf extract using enzymatic bioconversion by applying fermented cyclodextrin glycosyltransferase from Bacillus licheniformis DSM13. Two differently processed plant materials, namely dried and lyophilized Stevia rebaudiana plants, were extracted and compared. Following the bioconversion, the rebaudioside A content was on average doubled. The maximum increase was fivefold with a 70–80% conversion of the stevioside.

Steviol glycosides are the intensely sweet components of extracts from Stevia rebaudiana. These molecules comprise an invariant steviol aglycone decorated with variable glycans and could widely serve as a low-calorie sweetener. However, the most desirable steviol glycosides Reb D and Reb M, devoid of unpleasant aftertaste, are naturally produced only in trace amounts due to low levels of specific β (1–2) glucosylation in Stevia. Here, we report the biochemical and structural characterization of OsUGT91C1, a glycosyltransferase from Oryza sativa, which is efficient at catalyzing β (1–2) glucosylation. The enzyme’s ability to bind steviol glycoside substrate in three modes underlies its flexibility to catalyze β (1–2) glucosylation in two distinct orientations as well as β (1–6) glucosylation. Guided by the structural insights, we engineer this enzyme to enhance the desirable β (1–2) glucosylation, eliminate β (1–6) glucosylation, and obtain a promising catalyst for the industrial production of naturally rare but palatable steviol glycosides., Steviol glycosides from the plant Stevia rebaudiana are already used as lowcalorie sweeteners, but the most abundant naturally occurring compounds have a bitter aftertaste. Here, the authors characterize and engineer rice glycosyltransferase OsUGT91C1 to facilitate the large-scale production of naturally rare but palatable glycosides Reb D and Reb M

Salinization of soil is a major problem affecting many plant physiological processes. The use of arbuscular mycorrhizal fungi (AMF) plays a key role in improving the growth and the crops yield. The aim of this study was to evaluate the combined effects of salt stress and AMF on agro-physiological and biochemical responses of Stevia rebaudiana Bertoni. The experiment was carried out in a completely randomized design with ten replicates under the green house conditions. Stevia plants were inoculated with AMF consortium (MC) or with Rhizophagus irregularis (Ri) on the presence (80 mM of NaCl) or the absence (0 mM of NaCl) of salt stress. The results showed that plant height, dry biomass of shoots and roots parts, mycorrhizal frequency and intensity, relative water content, chlorophyll fluorescence, stomatal conductance, chlorophyll a, and total chlorophyll were significantly reduced by 29%, 72%, 36%, 84%, 65%, 24%, 17%, 60%, 28.50%, and 40.9% respectively under salt stress. These changes were associated with a significant increase in antioxidant enzymes (activity of polyphenol oxidase, peroxidase, superoxide dismutase, and catalase), electrolyte leakage, lipid peroxidation, and hydrogen peroxide contents. The application of AMF (MC and Ri) improved growth and physiological parameters through rising the activities of antioxidant enzymes and reduction of the oxidative damage caused by the salt stress. The better results were recorded with MC-inoculated plants. These findings suggested that AMF could be an effective strategy to alleviate the adverse effects of salt stress on Stevia rebaudiana.

The steviol glycosides (SGs) in stevia (Stevia rebaudiana Bertoni) leaves are becoming increasingly valuable due to its high sweetness but low calorific value, which is driving the development of stevia commercial cultivation. Optimizing fertilization management can effectively increase SGs productivity, but knowledge on the relationship between potassium (K) fertilization and SGs production is still lacking. In this study, pot experiments were conducted in order to investigate the effect of K deficiency on SGs synthesis in stevia leaves, as well as the underlying mechanisms. Our results showed that when compared with standard K fertilization, K deficiency treatment has no significant effect on the biomass of stevia plant grown in a given soil with high K contents. However, K deficiency critically decreased leaf SGs contents as well as the expression of SGs synthesis-related genes. The contents of different sugar components decreased and the activities of sugar metabolism-related enzymes were inhibited under the K deficiency condition. Moreover, spraying sucrose on the leaves of stevia seedlings diminished the inhibitory effect caused by K deficiency. Our results also revealed the significant positive correlations between sucrose, glucose and SGs contents. Overall, our results suggest that K deficiency would suppress the synthesis of SGs in stevia leaves, and this effect may be mediated by the leaf sugar metabolism. Our findings provide new insights into the improvement of SGs production potential.

Plant cell and tissue culture makes provision of a sustainable and nature-friendly strategy for the production of secondary metabolites, and modern progress in gene editing and genome engineering provides novel possibilities to improve both the qualitative and quantitative aspects of such phytochemicals. The ever-expanding quest for plant-based medicine to treat diabetes facilitates large-scale cultivation of Stevia rebaudiana to enhance the yield of its much-coveted low-calorie sweetener glycosides. The potential to process stevia as a "natural" product should enhance the acceptance of steviosides as a natural calorie-free sweetener especially suitable for use in diabetic and weight control drinks and foods. Besides sweetener agents, S. rebaudiana is a potent source of many antioxidant compounds and is used to cure immunodeficiencies, neurologic disorders, inflammation, diabetes mellitus, Parkinson's disease, and Alzheimer's disease. This comprehensive review presents the research outcomes of the many biotechnological interventions implicated to upscale the yield of steviol glycosides and its derivatives in in vitro cell, callus, tissue, and organ cultures with notes on the use of bioreactor and genetic engineering in relation to the production of these valuable compounds in S. rebaudiana. KEY POINTS: • Critical and updated assessment on sustainable production of steviol glycosides from Stevia rebaudiana. • In vitro propagation of S. rebaudiana and elicitation of steviol glycosides production. • Genetic fidelity and diversity assessment of S. rebaudiana using molecular markers.

Objetive To compare the effect of Stevia rebaudiana in concentrations of 25 mcg. and 50 mcg. in the growth of Streptococcus mutans . Materials and Methods: The research was experimental in vitro. It was used Stevia rebaudiana sweeteners from the brands "Stevita" and "Stevia via" on S. mutans strains ATCC 35668. The strains were seeded in Petri dishes, containing Mueller Hinton agar, and the culture was incubated, in a microaerophilic jar, in a CO 2 atmosphere, for 24 and 48 hours at 35 ° C. Both of them sweeteners were diluted in distilled water, to allocate 100 ul of the solutions in 6 mm wells. of diameter. Finally, the inhibition halos were measured with a Vernier caliper. Results: For a statistical analysis a t student test was used, with a significance level (p

Stevia rebaudiana Bertoni is a plant species which is frequently used not only as a sweetener, but also for its antibacterial and antioxidant properties. Nowadays, there are a large number of studies on the antimicrobial and antioxidant activity of S. rebaudiana leaves, but there are almost no data about the antimicrobial and antioxidant potential of extracts from the other parts of S. rebaudiana. The aim of the present study is to provide data of the antibacterial and antioxidant potential of methanolic extracts from different parts of S. rebaudiana (flowers, leaves, stems, rhizomes, and tubers) cultivated in Bulgaria. Antibacterial activity of the extracts against Staphylococcus aureus, Bacillus cereus and Escherichia coli was evaluated by agar well diffusion method, rutin content - by HPLC method, total phenolic content and radical scavenging potential - by UV-Vis analysis. S. rebaudiana extracts demonstrated antibacterial activity mainly against S. aureus - flower extracts expressed the highest activity, followed by the leaf and stem extracts. Only flower and leaf extracts demonstrated very low antibacterial activity against B. cereus. S. rebaudiana extracts did not show any antibacterial activity against E. coli. Methanolic extracts of this plant are rich in antioxidants. The highest concentrations of rutin and total phenols were found in the rhizomes of the plants, followed by the leaves, tubers, flowers, and stems, which corresponded to the radical scavenging potential of the same plant part. Comparisons between Trolox equivalents and gallic acid equivalents in different parts of S. rebaudiana on one hand, and Trolox equivalents and rutin concentration on the other hand showed a positive dependence and high values of the Pearson correlation - 0.9612 and 0.9707, respectively. The most important part of S. rebaudiana with medicinal significance (the leaves) has both comparatively good antibacterial activity and high antioxidant content, although the flowers and rhizomes expressed higher antibacterial and antioxidant activity, respectively. The experimental results imply that the cultivation area and climatic conditions of Bulgaria are very suitable for cultivation of S. rebaudiana plants with high content of antioxidants.

Introduction Stevia is known for its sweet taste, attributed to the presence of steviol glycosides. Although reports on the dynamic changes of steviol glycosides during development of stevia are available, the data are mainly focused on stevioside and rebaudioside A. Information concerning the comprehensive metabolite profile of stevia in relation to different developmental stages is still lacking. Objective This study investigated the metabolite changes along the developmental stages of a local stevia cultivar. Methodology Stevia leaves were harvested at 4 different developmental stages (early vegetative, late vegetative, budding, and flowering). Samples were then subjected to LC-MS metabolomics analysis to determine the metabolite variations. Results A total of 55 metabolites, comprising phenolic acids, flavonoids, and terpenoids were identified by MS/MS analysis of the stevia leaf extracts, revealing a metabolite profile which was comparatively similar with those of cultivars grown in other countries. PLS-DA differentiated the early vegetative stage stevia leaf samples from those of the later stages by higher content of phenolic acids. The leaf metabolomes of the later 3 stages (late vegetative, budding, and flowering) were collectively richer in flavonoids. Meanwhile, the content of steviol glycosides is highest during the late vegetative and budding stages. Conclusion The present study provided, for the first time, a general overview of the metabolite variations with regard to the different developmental stages of stevia. The information may facilitate decision making of suitable harvesting times for higher yields of steviol glycosides or a more balanced metabolite profile in terms of pharmacologically useful metabolites.

Stevia is primarily propagated through stem cuttings, and root growth in cuttings is vital for stevia to survive in the field. However, the genetic regulatory mechanism governing the root growth of stevia cuttings has not been fully elucidated to date. In this study, we isolated the AP2/ERF transcription factor SrERF5, which is a member of the B-3 subfamily with a typical AP2 domain. We observed that SrERF5 is specifically localized in the nucleus and exhibits relatively weak transactivation activity in yeast cells. The transcript of SrERF5 was determined to predominantly accumulate in roots and leaves, but was only detected at low levels in flowers, nodes and internodes. The transcription level of SrERF5 was elevated in the process of rooting and subsequently decreased at the late developmental stage. Constitutive expression of SrERF5 in Arabidopsis was observed to partly inhibit primary root growth through regulation of the expression levels of YUC genes. Taken together, the results of our study indicate that SrERF5 is a root growth modulator and may help to elucidate the regulatory mechanism and breeding manipulation of the rooting of stem cuttings in Stevia rebaudiana. This study was the first to isolate and functionally characterize a rooting-related AP2/ERF transcription factor in stevia, and this protein may represent a candidate essential regulator of root development in stem cuttings.

Diabetes mellitus is one of the main comorbidities associated with mortality and severe disease in infections with SARS-CoV-2. Extracts from the leaves of Morus alba and Stevia rebaudiana are used in traditional medicine to control diabetes. A brief review is made of the potential of these extracts to improve the conditions associated with COVID-19, not only through the control of diabetes but also for the presence of chemical compounds, particularly flavonoids, which have shown antiviral activity in pharmacological and in silico studies.

Stevia rebaudiana Bertoni is a commercially important natural sweetener plant and a boon to the diabetics. Unfortunately, its cultivation faces several abiotic and biotic constraints. Among the biotic ones, the most important is its poor competition with the weeds which culminates in 2-25% yield penalty and further raises the cultivation and production cost. Hence, weed management for successful Stevia cultivation is a major challenge faced by Stevia-farmers. Present study aimed at assessing the effects of mulching (organic and synthetic) and herbicides treatments for efficient weed control and improving the yield of Stevia. Maximum weed control was recorded with herbicides spray while significant improvement in plant growth characteristics like, plant height (98.2 cm average), branch number (5.1 plant−1), leaf number (415 plant−1) and dry weight were recorded in plots treated with rice straw (organic mulch: @ 15t. h−1). Maximum leaf biomass was recorded in plots treated with eucalyptus leaves (organic mulch: @ 15t. h−1) during the year 2017. It is concluded that herbicide spray controlled the weed growth while the crop yield and growth parameters were successfully enhanced by the use of mulche(s), in both the years (2017–18). Meticulous use of mulches or mulch plus limited herbicide(s) application for weed control, may ensure sustainable agriculture and shall ultimately decrease the dependability on synthetic herbicides.

E xplants play an important role in the propagation system of stevia ( Stevia rebaudiana Bertoni). A Completely Randomized Design (CRD) was used in this experiment with factorial pattern consisting of two factors, namely three types of explants (shoot tip, first node, and second node) and eleven accessions of stevia namely a 1 (Bogor), a 2 (Garut), a 3 (Canada), a 4 (Tawangmangu), a 5 (STG1), a 6 (SBG 4), a 7 (SBG 10), a 8 (SGB 2), a 9 (BR5), a 10 (SGR 7.5), a 11 (TR 3.5) . The results showed that shoot tip explant was the best explant th a n first node and second node for the number of shoots (18.11 shoots), number of leaves (93.49 leaves) and wet weight (3.56 grams). The best accession of shoot height was a 10 (S GR 7.5 ) (19.95 cm), the highest number of shoots was a 7 ( SBG 10 ) (21.87 shoots), the highest number of leaves was a 7 ( SBG 10 ) (138.00 leaves), the heaviest wet weight was a 7 ( SBG 10 ) (3.56 grams), the highest leaf chlorophyll content was a 10 (S GR 7.5 ) (0.63 µg mL -1 ). Accessions with the fastest root initiation time at the rooting stage w as a 1 1 ( TR 3.5 ) (4.00 DAC), the highest number of roots was a 10 ( TR 3.5 ) (27.11 roots), the best root length was a 2 ( Garut ) (4.51 cm) . Information on the best explant types and stevia accessions in the in-vitro multiplication stage can be used as the basis for stevia breeding programs in Indonesia. Abstract Eksplan berperan penting dalam sistem perbanyakan Stevia ( Stevia rebaudiana Bertoni). Penelitian ini menggunakan Rancangan Acak Lengkap (RAL) dengan pola faktorial yang terdiri dari dua faktor yaitu tiga jenis eksplan (ujung pucuk, ruas pertama, dan ruas kedua) dan sebelas aksesi stevia yaitu a 1 (Bogor), a 2 (Garut), a 3 (Canada), a 4 (Tawangmangu), a 5 (STG1), a 6 (SBG 4), a 7 (SBG 10), a 8 (SGB 2), a 9 (BR5), a 10 (SGR 7.5), a 11 (TR 3.5). Hasil penelitian menunjukkan bahwa eksplan ujung pucuk merupakan eksplan terbaik dibandingkan buku pertama dan kedua untuk jumlah tunas (18,11 tunas), jumlah daun (93,49 daun) dan berat basah (3,56 gram). Aksesi terbaik pada tinggi pucuk adalah a 10 (SGR 7.5) (19,95 cm), jumlah pucuk tertinggi a 7 (SBG 10) (21,87 pucuk), jumlah daun terbanyak a 7 (SBG 10) (138.00 helai daun), bobot basah terberat a 7 (SBG 10) (3,56 gram), kandungan klorofil daun tertinggi adalah GR 7,5 (0,63 µg mL -1 ). Aksesi dengan waktu inisiasi akar tercepat pada tahap perakaran adalah TR 3,5 (4,00 HST), jumlah akar terbanyak adalah TR 3,5 (27,11 akar), panjang akar terbaik adalah a 2 (Garut) (4,51 cm). Informasi jenis eksplan dan aksesi stevia terbaik pada tahap multiplikasi in-vitro dapat dijadikan dasar program pemuliaan stevia di Indonesia.

Stevia can be transformed using Agrobacterium tumefaciens-mediated method. Efficient and reproducible procedure for transformation of stevia (nodal sections) using herbicide-resistant bar gene has been documented, for effective weed management in stevia cultivation. Several parameters that influence T-DNA transfer and high-frequency recovery of stable transgenic plants including pre-conditioning of explants, Agrobacterium cell count, co-cultivation conditions, selection regime and supplements in shoot induction medium (SIM) and root induction medium (RIM) have been optimized. Supplementation of growth regulators in SIM and shoot elongation medium enhanced shoot formation. Half-strength MS medium as RIM promoted root induction. Overall, a 40% transformation frequency was achieved. This strategy of developing stable transgenics can be feasibly deployed for its reproducibility, efficiency and robustness for rapid recovery of non-chimeric, true transgenic plantlets. The protocol takes about 100 to 105 days from the start of co-cultivation to the planting of transformants into pots and does not alter the stevioside and rebaudioside contents.

Diabetes mellitus is a collection of symptoms that arise in someone who has increased blood glucose levels. The Stevia plant (Stevia rebaudiana Bert) contains a compound of diterpene glycosides as steviosida and rebaudiosida A. Purified extract of steviosida and rebaudiosida A is widely used as a sweetener for low calorie food and beverage products or as a sugar substitute for diabetics and has the effect of lowering blood sugar levels. This study aims to determine the antidiabetic effect of microencapsulated preparations of Stevia leaf extract (Stevia rebaudiana) with a combination of inulin chitosan encapsulation. Antidiabetic mellitus test was carried out in vivo using test animals of male white rats of Wistar strain. The inducing compound that can cause the condition of diabetes mellitus test animals is Aloxan with a dose of 150 mg / kg Body weight of rats. given intraperitoneally for one day, then the mice were allowed to stand for 3 days to reach a state of diabetes mellitus. Blood glucose levels of test animals were measured on days 1 (initial), 5 (induction) and 12 (treatment) to determine the initial blood glucose levels, after induction of alloxan and after administration of test compounds both CMC Na 0.5% , glibenclamide, and preparations microencapsulation of Stevia leaf extract at a dose of 100; 300; and 700 mg / kg body weight. The results were obtained after 7 days of treatment, it was seen that blood glucose levels in the CMC group remained high, while the Glibenclamid administration group, and the three dosages of microencapsulation preparations of Stevia leaf extract could reduce blood glucose levels. This can be seen from the statistical test that there is a significant difference (p

Unmanned Aerial Vehicle (UAV) based remote sensing is one of the modern techniques for crop management, which has been used in this study for biomass and Nitrogen (N) level estimations for Stevia r...

Stevia rebaudiana is among recognized medicinal plants used as an artificial sweetener in food and drinks as it contains very low sugar content. It is recognized that stevia contains component steviol glycoside which contains stevioside and rebaudioside A has 50 to 100 more sweetness than sucrose. Due to this, stevia extraction of steviol glycoside is very demanded in the food and pharmaceutical industries. Research shows that stevioside levels are the highest at the time of flower bud formation and lower at the time preceding and following flower bud formation. Hence, this study aims to identify and characterize the putative gene that may involve in the flowering of local S. rebaudiana accession MS007 from the analysis of bioinformatics tools. The outcome of this study will help further in the study of the manipulation of the flowering process to increase the outcome yield of steviol glycoside. This study involves characterization of putative zinc finger ZAT10 gene by homology search by BLAST, protein domain search using InterPro, physicochemical analysis using ProtParam and TMHMM, multiple sequence alignment using MUSCLE, and phylogenetic tree construction using MEGA. The bioinformatics analysis using these programs and software manages to identify the protein domain of ZAT10 which shows the function of metal ion binding and involve in transcriptional regulation. The analysis of the phylogenetic tree also shows that ZAT10 protein may have a recent common ancestor in its own Asteraceae families such as Lactuca sativa and Heliantus annus.

Background Stevia rebaudiana is a high value crop due to the strong commercial demand for its metabolites (steviol glycosides) but has limited geographical cultivation range. In non-native environments with different daylength and light quality, Stevia has low germination rates and early flowering resulting in lower biomass and poor yield of the desired metabolites. In this study, artificial lighting with light-emitting diodes (LEDs) was used to determine if different light quality within and outside of the photosynthetically active radiation (PAR) range can be used to improve germination rates and yields for production of steviol glycosides for the herbal supplement and food industry. Results Plants treated with red and blue light at an intensity of 130 μmol m-2 s-1 supplemented with 5% of UV-A light under a 16-h photoperiod produced the most desirable overall results with a high rate of germination, low percentage of early flowering, and high yields of dry leaf, stevioside and rebaudioside A, 175 days after planting. Conclusion While red and blue light combinations are effective for plant growth, the use of supplemental non-PAR irradiation of UV-A wavelength significantly and desirably delayed flowering, enhanced germination, biomass, rebaudioside A and stevioside yields, while supplemental green light improved yield of biomass and rebaudioside A, but not stevioside. Overall, the combination of red, blue and UV-A light resulted in the best overall productivity for Stevia rebaudiana. © 2021 Society of Chemical Industry.

Transcriptome analysis revealed the potential mechanism of nitrogen regulating steviol glycosides synthesis via shifting of leaf carbon metabolic flux or inducing certain transcription factors. Nitrogen (N) plays key regulatory roles in both stevia (Stevia rebaudiana) growth and the synthesis of its functional metabolite steviol glycosides (SGs), but the mechanism by which this nutrient regulates SGs synthesis remains to be elucidated. To address this question, a pot experiment was performed in a greenhouse where stevia plants fertilized with N (the control as CK plants) and compared with plants without the supply of N. Physiological and biochemical analyses were conducted to test the growth and metabolic responses of plants to N regimes. Our results showed that N deficiency significantly inhibited plant growth and leaf photosynthesis, while increased leaf SGs contents in stevia (49.97, 46.64 and 84.80% respectively for rebaudioside A, stevioside, and rebaudioside C), which may be partly due to "concentration effect". Then, transcriptome analysis was conducted to understand the underlying mechanisms. A total of 535 differentially expressed genes were identified, and carbon metabolism-related events were highlighted by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes. Many of these genes were significantly upregulated by N-deficiency, including those involved in "phenylpropanoid biosynthesis", "flavonoid biosynthesis" and "starch and sucrose metabolism". Our study also analyzed the expression patterns of SGs synthesis-related genes under two N regimes and the potential transcription factors linking N nutrition and SG metabolism. N-deficiency may promote SGs synthesis by changing the carbon metabolism flux or inducing certain transcription factors. Our results provide deeper insight into the relationship between N nutrition and SGs synthesis in stevia plants.

The review presents the current state of the science for stevia (Stevia rebaudiana Bertony), its biochemical composition, therapeutic properties and using in the food industry. Interest in this plant, a source of natural low-calorie sweeteners, is associated with increased consumption of dietary sweeteners, caused by an increase in the number of patients with diabetes, metabolic syndrome, and with many negative effects from the use of synthetic sweeteners. Diterpene glycosides from stevia have a high sweetness (50-350 times sweeter than sucrose), low calorie content, safe for human health. In addition to them, a number of biologically valuable compounds (mineral elements, vitamins, proteins, amino acids, oligosugars, fiber, polyphenols) were found in the leaves of stevia. High antioxidant properties of stevia leaf extracts has been shown, which allows them to be used in the food industry in the production of functional products. Numerous data have been obtained on the various therapeutic properties of stevia. It has been revealed that regular use of stevia glycosides reduces blood glucose and cholesterol levels, promotes cell regeneration, inhibits the growth of tumor cells and strengthens blood vessels. Components from stevia leaves have a choleretic, diuretic effect, normalize blood pressure, prevent diseases of the gastrointestinal tract, and have a beneficial effect on kidney function. Stevia extracts also have antibacterial, antiviral, anti-inflammatory and immunomodulatory effects. The safety and stability of stevia sweet glycosides in an acidic environment and at high temperatures allows them to be widely used in the production of products such as diet drinks, teas, sauces, marinades, seafood, ice cream, yogurts, pastries, culinary products and sweets.

Aims: Stevia rebaudiana which is commonly known as sweet leaf herb is used to extract non caloric sweet steviol glycosides. Thus based on available reports about its chemical composition, biosynthesis of steviol glycosides, application, cultivation, and phytochemical screening an attempt has been made to review to Stevia rebaudiana in context of its medicinal and pharmaceutical importance. Methodology: Literature search have been done in the web using google scholar, PubMed as search platform. More than two-thirds of the references are within 15 years. Results: According to the literature search S. rebaudiana leaves contain non caloric steviol glycosides and pharmaceutically important other phytochemicals. Miccropropagation is the best propagation method to overcome difficulties in conventional propagation methods. Conclusion: It is concluded that in vitro cultures has potential to extract important phytochemicals used in various pharmaceutical, food (flavoring agents, food additives) and perfume industries.

A study was conducted in Al-Seba Reserve / Basra Governorate to study the effect of nitrogen and potassium fertilization on growth of stevia plants during 2018-2019 agricultural season, in pots. A sandy mixture of soil was used and two factors were studied: the first factor was urea fertilizer with five levels of nitrogen (N0 0, N1100, N2150, N3 200, and N4 250 kg / ha) and the second factor was potassium sulfate with three levels of potassium (K0 0, K1 75 and K3150 kg /h (. The experiment was experimental factor using a complete randomized design (C.R.D) with three replications. The results showed a significant effect of adding nitrogen and potassium fertilizers and there interaction on: plant height, number of branches, leaf area index, and the treatment N3K2 gave the highest yield reached (1.27 tons. h-1), and N4K2 recorded a highest content of Rebaudioside A (53.26 ppm).

Performances of crops are mainly influenced by frost, heat and availability of soil-water and nitrogen (N). However, little is known about the interaction between soil-water and N on Stevia rebaudiana. Thus, a field experiment was conducted with fifteen treatment combinations comprising three levels of soil-moisture (irrigation at 20, 50 and 75 kPa soil-water-potential) and five N levels (0–140 kg ha−1) to understand how soil-moisture and N influence growth, physiological and biochemical activities of stevia. Plants irrigated at 50 kPa registered 6.3–18.9% and 20.7–21.2% higher dry leaf yield compared with 20 and 75 kPa, respectively. No significant (P ≥ 0.05) differences in concentrations of total steviol glycosides (TSGs) in leaf were found due to moisture regimes. Total soluble sugars (TSS), proline, total phenols were decreased significantly (P ≤ 0.05) with plants irrigated at 20 kPa whereas SOD, CAT, and POX were decreased at both excessive and deficit water conditions. Photosynthetic rate (PN) and stomatal conductance (gs) decreased with plant irrigated at 75 kPa. Anatomical changes in leaf were also observed due to different moisture regimes. Among the N levels, 105 kg ha−1 registered approximately 50–53% higher dry leaf yield compared with control (0 kg N ha−1), irrespective of irrigation level. Excess (140 kg ha−1) and shortage of N significantly decreased the PN, gs, and enzyme activities. Concentrations of TSS and TSGs were higher with N at 105 and 70 kg ha−1, respectively. Our results emphasize that irrigation at 50 kPa and application of N 105 kg ha−1 is the suitable combination for sustainable cultivation of stevia.

Abstract Steviol glycosides (SvGls) are plant secondary metabolites belonging to a class of chemical compounds known as diterpenes. SvGls have been discovered only in a few plant species, including in the leaves of Stevia rebaudiana Bertoni. Over the last few decades, SvGls have been extensively researched for their extraordinary sweetness. As a result, the nutritional and pharmacological benefits of these secondary metabolites have grown increasingly apparent. In the near future, SvGls may become a basic, low-calorie, and potent sweetener in the growing natural foods market, and a natural anti-diabetic remedy, a highly competitive alternative to commercially available synthetic drugs. Commercial cultivation of stevia plants and the technologies of SvGls extraction and purification from plant material have already been introduced in many countries. However, new conventional and biotechnological solutions are still being sought to increase the level of SvGls in plants. Since many aspects related to the biochemistry and metabolism of SvGls in vivo, as well as their relationship to the overall physiology of S. rebaudiana are not yet understood, there is also a great need for in-depth scientific research on this topic. Such research may have positive impact on optimization of the profile and SvGls concentration in plants and thus lead to obtaining desired yield. This research summarizes the latest approaches and developments in SvGls production. Key points • Steviol glycosides (SvGls) are found in nature in S. rebaudiana plants. • They exhibit nutraceutical properties. • This review provides an insight on different approaches to produce SvGls. • The areas of research that still need to be explored have been identified.

La planta de stevia ('Stevia rebaudiana' Bertoni) es utilizada a nivel mundial como un edulcorante natural. Su cultivo es principalmente por su alto contenido de glucósidos y sus propiedades medicinales. El principal productor a nivel mundial es China, pero en los últimos años su cultivo se ha extendido a otros países, sobre todo en América Latina. En México, es un cultivo relativamente nuevo e innovador. Por la generación de empleos y los beneficios a la salud, stevia podría ser una propuesta de cultivo para el estado de Tabasco. Sin embargo, su sensibilidad a la humedad y la falta de información relacionada a su adaptación local hacen cuestionable su cultivo. Por ello, para conocer su adaptación, crecimiento y producción bajo las condiciones ambientales de la zona, se establecieron plantas de stevia variedad Morita II, en la comunidad de la Huasteca, Centro, Tabasco durante el período de diciembre 2019 a marzo 2020.

Steviol glycosides (SGs) and gibberellins (GAs) share the same molecular basis. However, the coordination of their respective biosynthetic pathways is very intriguing. Thus, the present study aimed to investigate the role of plant growth regulators, gibberellic acid (GA3), chlorocholine chloride (CCC), and paclobutrazol (PBZ), on the metabolism of Stevia rebaudiana and identify possible ameliorates of the evaluated parameters when CCC and PBZ-treated plants were subsequently treated with GA3. For this, explants were cultured in the absence or presence of 2 mg L−1 GA3, CCC, or PBZ (Step 1). After 20 days, half explants incubated with CCC and PBZ were treated with 2 mg L−1 GA3 and the other half, as well as the rest of the explants, were sub-cultured in their respective initial conditions for 20 days (Step 2). GA3-treated plants showed increased stevioside and phenolic compounds content, as well as a downregulation of most of the SGs/GAs biosynthesis-related genes, with a more pronounced effect upstream of steviol. Following this trend, CCC downregulated some MEP pathway genes, including SrDXS, SrDXR, SrCDPS, and SrKS, and upregulated SrUGT6G1. PBZ also upregulated SrUGT76G1 and inhibited five genes of the MEP pathway and all genes coding for kaurenoid pathway enzymes. The obtained results highlight the capability of GA3 to reverse the negative effects of PBZ on the pattern of many transcripts and to additionally increase the stevioside content to levels comparable to those found in field-grown plants. A feedback loop in in vitro cultured stevia plants in response to GA3, CCC and PBZ was demonstrated. GA3-treated plants showed increases in stevioside and phenolic compound contents.

Stevia rebaudiana (Bertoni) is known as a natural sweetener plant to produced steviol glycosides. The steviol glycosides biosynthesis is limited in S. rebaudiana plants due to the alteration in the environmental circumstances such as drought, cold, salt and light. These environmental circumstances are a common side-effect in plants affecting the plant growth, metabolism and yield of secondary metabolites. Due to absence of complete genome annotations, the plant metabolites signaling is difficult in order to get the exact enzymatic flow to the product. In this article, we have analyzed the ESTs of S. rebaudiana and predicted their role in plant signaling in term of cis-regulatory elements, their biological function respect to abiotic stress. Further, the predicted abiotic stress responsive factors were also analyzed in order to predict the relevant genes or proteins function in comparison with the genome of Arabidopsis thaliana. Total 5,548 ESTs of stevia were retrieved from NCBI database. EST-contigs assembled from 5393 were 619 contigs and 2,894 singletons elements were identified by assembler program. Due to short expressed sequences related to singletons, it is excluded for further study. Further, retrieved ESTs were resulted in to 619 EST-contigs by using the clustering method. Out of 619, 15 contigs belongs to transcription factor families while 292 contigs, belongs to five enzyme classes. Out of 619 contigs, the 529 contigs showing the correct gene ontology in term of biological process (BP), molecular Functions (MF) and cellular component (CC). Further, these contigs were also screened for metabolic pathways analyses using KEG database. In this, 390 metabolic pathways and 67 involved for signal transduction were identified from 619 contigs. The co-expression analysis was revealed by gene investigators and STRING 10.0 with 0.40 correlations and 0.9 mutual connection. In projected PPI network, the recognized factors (WD40-like protein, MYB-HB like, AP2-EREBP, C2H2, Hap3/NF-YB, bHLH, C2C2-CO-like, CW-Zn, FHA-SMAD, Nin like, SBP3, TIFY, Tc-PD, Znf-B and bIP) belong to plant signaling and MAPK signaling pathways. These TFs introduce as a candidate genes responsive factors may lead to enhanced plant growth and metabolism by overexpression.

Recycling of ligno-cellulosic residues and economically viable crops production with improved water use efficiency is imperative to secure high-quality sustainable food production and implement the environmental sustainability. Therefore, the objective of this work was to evaluate superabsorbent sugarcane bagasse polymer composite (SBP) on Stevia rebaudiana quality and production under deficit irrigation. The experiment was conducted at Sabahia Agricultural Research Station, Alexandria, Egypt during two seasons 2017/2018 and 2018/2019 under the greenhouse conditions. Three SBP treatments (0.0, 2.0 and 4.0 g/5 kg of soils) using three irrigation levels (100%, 70% and 50% of field capacity) were applied. Data revealed that the soil amendment with SBP enhanced and gave the highest values of stevia growth parameters, chlorophyll, total soluble carbohydrate and steviol glycoside (SVglys) under both irrigation systems in both seasons. The SBP at dosage 2 and 4% levels into the soil led to an increase of dry leaves yield by 1.5 and 1.32 fold, respectively compared to yield in untreated soil under 70% field capacity. Calculated SVglys and determined by IR was high in soil amendment with 2.0% SBP (15.60%) under 100% irrigation levels and nearly closed in 70% irrigation level (15.02%). SBP application under deficit irrigation conditions increased of amount WUE and showed improvement in peroxidase isozyme system that can be used as a biomarker for characterizing drought stress tolerance. Hence, it could be recommended that SBP can be used to enhance the stevia productivity and enabled the survival of stevia plant under deficit irrigation conditions.

Leaf area measurement is pivotal for plant physiologists. Hence, accurate measurement of their leaf area is incredibly relevant in agronomic terms. The plant Stevia rebaudiana is a sucrose-free plant species that is now vital to the global production of sucrose-free foods. Here, we estimated S. rebaudiana leaf area using a nondestructive methodology comprising allometric equations. Through leaf length (L), leaf width (W), and/or their product (LW) the leaf area was determined. One thousand leaves were sampled from four distinct S. rebaudiana genotypes for model construction. Linear or power models were generated, and the best equation was selected using a statistical criterion. The statistical criteria indicated that the linear models best suited all genotypes tested, included a function of LW, exhibited increased stability, and precisely estimated coefficients. ANOVA revealed that both generalized and combined equations were feasible. Nevertheless, grouping all genotypes into a single model was not possible as the genotype leaf architectures were very dissimilar.

Dried stevia leaves (Stevia rebaudiana Bertoni) were used as objects of research. We studied the leaves of stevia varieties Ramon sweetener grown in the Penza region, the leaves of stevia varieties Ramon sweetener grown in the Tver region, Krasnodar region, the Republic of Crimea, as well as imported raw stevia from India and Paraguay. The purpose of this work is a comparative study of the amino acid composition of raw stevia grown in different conditions. The amino acid composition of stevia leaves (Stevia rebaudiana Bertoni) was revealed by capillary electrophoresis.13 amino acids were identified, of which eight are "essential" (lysine, phenylalanine, histidine, leucine, isoleucine, methionine, valine, threonine). The proportion of essential amino acids in stevia raw materials ranged from 2.99 to 4.64%. The content of interchangeable acids was: tyrosine from 0.24% to 0.36%, Proline from 0.44 to 0.68%, serine from 0.77 to 1.03%, alanine from 0.48 to 0.83%, glycine from 0.40 to 0.68%. The total amount of amino acids detected is higher in the Ramon sweetener variety grown in the Penza region (9.52%) compared to other samples, the lowest amount is found in stevia grown in Paraguay (6.46%). The results obtained indicate the prospects for further studies of the amino acid composition of Stevia rebaudiana and can characterize this species as a source of valuable medicinal substances with a wide range of pharmacological activity.

Stevia (Stevia rebaudiana Bertoni L) is one of the potential alternative commodities for non-caloric sugar producers, so it is safe for health. However, until today, information on stevia cultivation technology has not been widely reported. This research aimed to determine the effect of clones and plant spacing on stevia growth. It was carried out in the Experimental Garden (EG) of Cobanrondo, Balai Penelitian Tanaman Pemanis and Serat (Balittas) , at an altitude of 1450 m above sea level, from September to November 2012. The research was arranged in a factorial using a randomized block design with three replications. The first factor was the stevia clones from Bogor, consisting of 2 types of clones: wide-leaf clones and narrow-leaf clones. The second factor is the plant spacing composed of 2 levels: a narrow plant spacing (25 cm x 25 cm) and a wide plant spacing (40 cm x 40 cm). The plot size was 2 m x 2 m. Observations were made on plants aged 14 days after planting (DAP), 28 DAP, and 46 DAP on plant height, canopy width, number of leaves, dry weight of leaves, and dry weight of leafless stover. The research results showed that plant spacing affected plant height at 46 DAP and canopy width at 28 and 46 DAP. Narrow spacing produces taller plants than wide plant spacing, whereas clones affected plant height at 28 DAP and 46 DAP and the number of leaves at 46 DAP. Plant spacing, varieties, and interactions did not affect dry leaf weight and leafless stover weight at 46 DAP. Thus, stevia clones, both narrow and wide-leaf, are recommended at a narrow plant spacing.

Plants under different environmental regimes exhibit phenotypic plasticity, sometimes producing more secondary metabolites when microenvironmental conditions are manipulated but these responses may be species, cultivar and/or genotype dependent. To test the hypothesis of whether in vitro plants of S. rebaudiana Bertoni would accumulate higher amounts of steviol glycosides when plants were growing under salt and drought stress, cultivar ST2100 plants were used. We thus applied 25 to 100 mM NaCl and polyethylene glycol 6000 (PEG) at 2.5% to 10.0% (w/v) to generate different Murashige and Skoog (Physiol Plant 15:473–497, 1962) media. Microplant cultures were also profiled for stevioside, rebaudioside A and steviol via LC–MS. Essential oil chemicals and fatty acids were assessed using GC–MS. Finally, a chemometric analysis of ethanolic extracts produced from treated and control plants is presented from MSE fragmentation data and various phenolic acids were tentatively identified using ion fragmentation patterns. Increasing amounts of both NaCl and PEG led to poor growth and development in cultures of S. rebaudiana. For example, the 25 and 50 mM NaCl-treated plants had fewer roots in comparison to controls and at even higher concentrations (75 and 100 mM NaCl), plants did not to root. Poor in vitro organogenesis was more pronounced with PEG. For instance, when plants were placed on a 10% PEG-medium, the ability for shoot regeneration was lost and callus became more apparent. Increasing levels of NaCl and PEG were also correlated to lowered levels of rebaudioside A and stevioside. In relation to the control plants that had 0.054 mg g−1 FW of steviol, the 25 mM NaCl treatment group had highest levels of this compound, recorded at 0.156 mg g−1 FW. All other salt treatments led to trace amounts of this chemical (0.005–0.009 mg g−1 FW) and it was not detected in any of the PEG-treated plants, except for the controls. The PCA loadings plots exposed stevioside, rebaudioside E and a steviol glycoside derivative as the MS signals that contributed to discriminant clusters segregating controls from the NaCl-treated groups. For PEG, segregation in the PCA is mostly influenced by dicaffeoylquinic acid as a marker ion, separating the controls from the treatment groups. PEG-treatments caused more prominent changes to the essential oil chemistry of Stevia plants. This was evident when 7.5 or 10% PEG was applied as sabinene, α-terpinolene, n-amyl isovalerate, 7-octen-4-ol, α-bergamotene, junipene, (+)-calarene, α-cadinol, β-pinene, α-bergamotene, (+)-calarene and junipene became undetectable. Changes of this nature may be undesirable when aromatic oils of S. rebaudiana are targetted for commercial markets as our data suggest adjustment to stresses may negatively impact volatile compounds leading to a loss of bioactive aromatic compounds. This study reports, for the first time, the effects of salinity and drought conditions in vitro on changed essential oil profiles of S. rebaudiana, providing new insights into the effects of stress on the essential oil chemistry of S. rebaudiana. Stevia responses to salt and drought stresses in vitro lead to lowered measured steviol glycosides (i.e stevioside, rebaudioside A and steviol) and significantly changes the essential oil terpenoid profiles

Melatonin has been shown to play a variety of roles in regulating plant growth and response to various abiotic stresses, but its main function remains unclear in response to NaCl toxicity. The aim of the current study was to evaluate the effect of melatonin (0, 5, 10, and 20 μM) on growth, photosynthetic pigments, compatible solutes, ionic homeostasis, enzymatic and non-enzymatic antioxidants, the content of steviol glycosides, and expression of kaurenoic acid hydroxylase (KAH) and uridine diphosphate glycosyltransferase (UGTs) genes in stevia under 25 mM NaCl in in vitro culture. The results showed that in the presence of 25 mM NaCl, melatonin at 5 and 10 μM improved growth parameters, photosynthetic pigments, proline, and soluble sugar contents and reduced electrolyte leakage in stevia leaves. Interestingly, melatonin (5 and 10 μM) reduced the accumulation of malondialdehyde and the level of ROS by improving the redox state of the ascorbate-glutathione cycle and the activity of antioxidant enzymes. Additionally, melatonin decreased the accumulation of Cl and Na and improved the accumulation of K, N, Ca, and P, thus maintaining the ionic balance in leaves under NaCl toxicity. Melatonin increased the accumulation of rebaudioside A and stevioside in the leaves under salinity by upregulating the expression level of KAH and UGTs genes. However, high concentrations of melatonin (20 μM) exacerbated the negative effects of salinity and further reduced stevia growth under salinity. Therefore, the current study indicates the protective role of melatonin in the appropriate concentration in stevia against NaCl toxicity in in vitro conditions.

Stevia (Stevia rebaudiana Bertoni) possesses substantial value for its unique sweet compounds-steviol glycosides (SGs). In the metabolic glycosylation grid of SGs, SrUGT91D2 has been shown to catalyze formation of 1,2-β-d-glucoside linkages at the C13- and C19-positions and play a crucial role in the synthesis of SGs, including the formation of stevioside (ST), rebaudioside E (RE), and rebaudioside D (RD). However, the key residues of the SrUGT91D2 enzyme and how SrUGT91D2 affects the accumulation of SGs in S. rebaudiana remain unclear. In the present study, cloning and functional analysis of full-length SrUGT91D2 gene sequences were performed in 10 different S. rebaudiana genotypes with divergent SG compositions. After sequence analysis, it was found that most of the sequences of this gene (more than 50%) in each genotype were consistent with the UGT91D2e_No.5 allele, which has been reported to exert catalytic activity on 1,2-β-d-glucoside. Moreover, six variants (UGT91D2e_No.5, SrUGT91D2-11-14, SrUGT91D2-110, SrUGT91D2-023, SrUGT91D2-N01, and SrUGT91D2-N04) of this gene were obtained, and their activities were identified. Although there were some differences among these variants, the only type of mutation was partial base substitution at a very low level. In addition, the expression analysis of SrUGT91D2 in each genotype showed that the expression level of the gene was significantly different among genotypes, and a significant positive correlation was found between the content of RD (which was closely influenced by SrUGT91D2) and the expression level of SrUGT91D2 in each genotype (correlation coefficient = 0.91). Thus, it was indicated that SrUGT91D2 was relatively conserved in S. rebaudiana, and the differential effect of SrUGT91D2 on the accumulation of related SGs mainly derived from its expression level. Furthermore, based on homologous modeling and molecular docking analysis, T84, T144, A194, S284, E285, V286, G365, E369, R404, and G409 were predicted to be key residues in the glucosylation of SGs by SrUGT91D2. After site-mutation and enzyme assays, it was confirmed that T84, T144, R404, A194, and G409 are the key residues in the SrUGT91D2 protein, especially T144 and G409. This work provided valuable information for understanding the structure-activity relationship of the SrUGT91D2 protein and the molecular mechanism of SG accumulation in stevia.

Stevia rebaudiana Bertoni is commonly called stevia and mostly found in the north east regions of South America. It is an herbaceous and shrubby plant belonging to the Asteraceae family. Stevia is considered as a natural sweetener and a commercially important plant worldwide. The leaves of S. rebaudiana contain steviol glycosides (SGs) which are highly potent and non-caloric sweeteners. The sweetening property of S. rebaudiana is contributed to the presence of these high potency, calorie free steviol glycosides. SGs are considerably suitable for replacing sucrose and other artificial sweetening agents which are used in different industries and pharmaceuticals. SGs amount in the plant mostly varies from 8% to 10%, and the enhancement of SGs is always in demand. These glycosides have the potential to become healthier alternatives to other table sugars for having desirable taste and zero calories. SGs are almost 300 times sweeter than sucrose. Being used as alternative sugar intensifier the commercial value of this plant in biopharmaceutical, food and beverages industries and in international market is increasing day by day. SGs have made stevia an important part of the medicinal world as well as the food and beverage industry, but the limited production of plant material is not fulfilling the higher global market demand. Therefore, researchers are working worldwide to increase the production of important SGs through the intercession of different biotechnological approaches in S. rebaudiana. This review aims to describe the emerging biotechnological strategies and approaches to understand, stimulate and enhance biosynthesis of secondary metabolites in stevia. Conventional and biotechnological methods for the production of steviol glycosides have been briefly reviewed and discussed.

Stevia rebaudiana Bertoni and Mentha piperita are plants that generate interest mainly due to the presence of bioactive compounds in their leaves, such as phenolics. Studies indicate that phenolics have pharmacological and therapeutic properties, including antioxidant activity. Phenolic compounds may be affected by the type of fertilization. For this reason, organic and chemical fertilization were evaluated along with antioxidant activity. Results showed significant differences for total phenols in organic peppermint (62% higher content). Also, DPPH test displayed differences for peppermint and stevia (572% and 16% greater in organic). Organic fertilization may be alternative for producing high added agricultural and commercial products.

Three mixture designs were used to characterize herbal formulations for infusions prepared with cedron, boldo, and yerba mate in addition to stevia. This study aimed to investigate if the inclusion of stevia in infusions could affect the recovery of phenolic compounds with antioxidant activity. Infusions with higher phenolic content and higher antioxidant activity were obtained when yerba mate or boldo predominated in the infusion. The highest tannin content was found in mixtures containing yerba mate, boldo, and stevia, while the minimum tannin contents were found in some cedron infusions. The content of steviol glycosides increased as the proportion of stevia increased in the infusions. In general, the recovery of natural sweeteners or phenolic compounds with antioxidant activity exhibited different patterns, depending on the components of the infusions. The presence of stevia and steviol glycosides did not influence the recovery of phenolic compounds with antioxidant activity. SUPPLEMENTARY INFORMATION: The online version of this article (10.1007/s13197-021-04979-9)

A global rise in CO2 concentration and temperature levels can impact the living part of the earth including the plants. Stevia or candy leaf (Stevia rebaudiana Bertoni) is a medicinal aromatic plant that produces several useful chemical compounds. Studies were carried out in a fully automated greenhouse in order to determine the response of aromatic compounds of stevia leaves to different CO2 concentrations and temperature levels. This study had four treatments including (1) 26 ± 1/16 ± 1 °C day/night temperature plus 400 ± 50 ppm CO2 concentration [control], (2) 29 ± 1/19 ± 1 °C day/night temperature plus 600 ± 50 ppm CO2 concentration, (3) 32 ± 1/22 ± 1 °C day/night temperature plus 800 ± 50 ppm CO2 concentration and (4) 35 ± 1/25 ± 1 °C day/night temperature plus 1000 ± 50 ppm CO2 concentration. Results of the study showed that yield of total aromatic compounds ranged between 12.65 and 13.65 μg/g for stevia . Generally, concentrations of the compounds such as ketones, aldehydes and alcohols were decreased with increase in concentration of CO2 and temperature. Terpenes were the compounds whose concentrations were increased with increase in concentration of CO2 and temperature. The climatic conditions did not cause a significant change in the aromatic compounds of stevia.

Since the medicinal plants mainly are cultivated in marginal areas, are exposed to environmental stresses such as salinity, more than other plants. Salt stress causes damage to photosynthetic process, carbohydrates assimilation and photosystem I and II. However, recently, the role of fungi coexistence and polyamines in plants tolerance to saline conditions are pronounced. Therefore, the present study was conducted to evaluate the effects of endophyte symbiosis and spraying of polyamine spermidine (Spd) on chlorophyll fluorescence parameters of stevia (Stevia rebaudiana Bertoni) medicinal plant under irrigation with saline water. Treatments included non-inoculation (Control) or co-inoculation of Piriformospora indica + Trichoderma virens (Pi + Trich), foliar application of Spd (0 and 0.75) and three salinity levels of Caspian sea water (0, 6 and 12 dS m–1). Seedlings of stevia were transplanted in field conditions and were sprayed with Spd solutions after 9 weeks of planting. Seven days later, the plants were irrigated with three saline treatments for two weeks. The results showed that the foliar application of Spd had a positive effect on Fm, Fv and Fv/Fm and negative effect on Y(NO). Irrigation of plants with saline water had an adverse effect on fluorescence parameters. However, fungi inoculation markedly increased Fm, Fv, Fv/Fm and Y(II) while decreased Fo, Y(NPQ) and Y(NO) in all levels of salt stress. Fungal inoculation and Spd application with 0.75 mM remarkably enhanced Fm. Generally, inoculation of endophytic fungi and Spd spraying improved the chlorophyll fluorescence parameters and adjusted adverse effects of salinity stress in stevia plants.