Selenium Biofortification Impacts the Tomato Fruit Metabolome and Transcriptional Profile at Ripening.

In the present work, the effects of enriching tomatoes with selenium were studied in terms of physiological, metabolic, and molecular processes in the last stages of fruit development, particularly during ripening. A selenium concentration of 10 mg L-1 with sodium selenate and selenium nanoparticles was used in the spray treatments on the whole plants. No significant effects of selenium enrichment were detected in terms of ethylene production or color changes in the ripening fruit. However, selenium enrichment had an influence on both the primary and secondary metabolic processes and thus the biochemical composition of ripe tomatoes. Selenium decreased the amount of ß-carotene, increased the accumulation of naringenin and chlorogenic acid, and decreased the coumaric acid level. Selenium also affected the volatile organic compound profile, with changes in the level of specific apocarotenoid compounds, such as ß-ionone. These metabolomic changes may, to some extent, be due to the impact of selenium treatment on the transcription of genes involved in the metabolism of these compounds. RNA-seq analysis showed that the selenium application mostly impacted the expression of the genes involved in hormonal signaling, secondary metabolism, flavonoid biosynthesis, and glycosaminoglycan degradation.

Iodine biofortification of Swiss chard (Beta vulgaris ssp. vulgaris var. cicla) and its wild ancestor sea beet (Beta vulgaris ssp. maritima) grown hydroponically as baby leaves: effects on leaf production and quality.

BACKGROUND: About 35-45% of the global population is affected by iodine deficiency. Iodine intake can be increased through the consumption of biofortified vegetables. Given the increasing interest in wild edible species of new leafy vegetables due to their high nutritional content, this study aimed to evaluate the suitability of Swiss chard (Beta vulgaris ssp. vulgaris var. cicla) and its wild ancestor sea beet (Beta vulgaris ssp. maritima) to be fortified with iodine. Plants were cultivated hydroponically in a nutrient solution enriched with four different concentrations of iodine (0, 0.5, 1.0, and 1.5 mg L-1 ), and the production and quality of baby leaves were determined. RESULTS: Sea beet accumulated more iodine than Swiss chard. In both subspecies, increasing the iodine concentration in the nutrient solution improved leaf quality as a result of greater antioxidant capacity - the ferric reducing ability of plasma (FRAP) index increased by 17% and 28%, at 0.5 and 1.5 mg L-1 iodine, respectively - the content of flavonoids (+31 and + 26%, at 1 and 1.5 mg L-1 of iodine, respectively), and the lower content of nitrate (-38% at 1.5 mg L-1 of iodine) and oxalate (-36% at 0.5 mg L-1 of iodine). In sea beet, however, iodine levels in the nutrient solution higher than 0.5 mg L-1 reduced crop yield significantly. CONCLUSIONS: Both subspecies were found to be suitable for producing iodine-enriched baby leaves. The optimal iodine levels in the nutrient solution were 1.0 in Swiss chard and 0.5 mg L-1 in sea beet, as crop yield was not affected at these concentrations and leaves contained enough iodine to satisfy an adequate daily intake with a serving of 100 g. © 2023 Society of Chemical Industry.

Se-Enrichment Pattern, Composition, and Aroma Profile of Ripe Tomatoes after Sodium Selenate Foliar Spraying Performed at Different Plant Developmental Stages.

Foliar spray with selenium salts can be used to fortify tomatoes, but the results vary in relation to the Se concentration and the plant developmental stage. The effects of foliar spraying with sodium selenate at concentrations of 0, 1, and 1.5 mg Se L-1 at flowering and fruit immature green stage on Se accumulation and quality traits of tomatoes at ripening were investigated. Selenium accumulated up to 0.95 µg 100 g FW-1, with no significant difference between the two concentrations used in fruit of the first truss. The treatment performed at the flowering stage resulted in a higher selenium concentration compared to the immature green treatment in the fruit of the second truss. Cu, Zn, K, and Ca content was slightly modified by Se application, with no decrease in fruit quality. When applied at the immature green stage, Se reduced the incidence of blossom-end rot. A group of volatile organic compounds (2-phenylethyl alcohol, guaiacol, (E)-2-heptenal, 1-penten-3-one and (E)-2-pentenal), positively correlated with consumer liking and flavor intensity, increased following Se treatment. These findings indicate that foliar spraying, particularly if performed at flowering stage, is an efficient method to enrich tomatoes with Se, also resulting in positive changes in fruit aroma profile.

Selenium Enrichment Enhances the Quality and Shelf Life of Basil Leaves.

The biofortification of leafy vegetables with selenium (Se) is a good way to increase human dietary Se intake. In addition, selenium delays plant senescence by enhancing the antioxidant capacity of plant tissues, decreasing postharvest losses. We investigated the effects of selenium addition on the production and quality of sweet basil (Ocimum basilicum) leaves of two harvesting phases, hereafter referred to as cuts, during the crop cycle. Plants were hydroponically grown and treated with 0 (control), 4, 8 and 12 mg Se L-1 as selenate. To evaluate the growth, nutritional value and quality of the basil leaves, selected qualitative parameters were determined at harvest and after five days of storage. Application of Se at varying rates (4, 8 and 12 mg L-1) was associated with an increased leaf selenium concentration in the first, but not the second cut. The application of Se significantly affected the antioxidant capacity as well as the total phenol and rosmarinic acid contents at harvest. The reduction in ethylene production observed in the plants at 4 mg Se L-1 after five days of storage suggests that this Se treatment could be used to prolong and enhance the shelf-life of basil. The daily consumption of 10 g of Se-enriched basil leaves, which, as an example, are contained in a single portion of Italian pesto sauce, would also satisfy the recommended selenium supplementation in humans.

Red versus green leaves: transcriptomic comparison of foliar senescence between two Prunus cerasifera genotypes.

The final stage of leaf ontogenesis is represented by senescence, a highly regulated process driven by a sequential cellular breakdown involving, as the first step, chloroplast dismantling with consequent reduction of photosynthetic efficiency. Different processes, such as pigment accumulation, could protect the vulnerable photosynthetic apparatus of senescent leaves. Although several studies have produced transcriptomic data on foliar senescence, just few works have attempted to explain differences in red and green leaves throughout ontogenesis. In this work, a transcriptomic approach was used on green and red leaves of Prunus cerasifera to unveil molecular differences from leaf maturity to senescence. Our analysis revealed a higher gene regulation in red leaves compared to green ones, during leaf transition. Most of the observed DEGs were shared and involved in transcription factor activities, senescing processes and cell wall remodelling. Significant differences were detected in cellular functions: genes related to photosystem I and II were highly down-regulated in the green genotype, whereas transcripts involved in flavonoid biosynthesis, such as UDP glucose-flavonoid-3-O-glucosyltransferase (UFGT) were exclusively up-regulated in red leaves. In addition, cellular functions involved in stress response (glutathione-S-transferase, Pathogen-Related) and sugar metabolism, such as three threalose-6-phosphate synthases, were activated in senescent red leaves. In conclusion, data suggests that P. cerasifera red genotypes can regulate a set of genes and molecular mechanisms that cope with senescence, promoting more advantages during leaf ontogenesis than compared to the green ones.

Production of selenium-biofortified microgreens from selenium-enriched seeds of basil.

BACKGROUND: Microgreens (i.e. tender immature greens) are a popular alternative to sprouts (i.e. germinating seeds) because of their higher content of vitamins, carotenoids and phenols, as well as their lower content of nitrates. Their nutritional value can be improved by biofortification, which increases micronutrient levels during plant growth. Because selenium (Se) plays a significant role in antioxidant defense, biofortification with Se is a good way of improving the nutritional quality of sprouts and microgreens. The present study investigated the production of Se-fortified microgreens from Se-enriched seeds of sweet basil (Ocimum basilicum L.). These microgreens could be used as new beneficial dietary supplements. RESULTS: Basil plants were grown in a nutrient solution, containing 0 (control), 4 or 8 mg Se L-1 as sodium selenate, to full maturity. Seeds accumulated a high amount of Se and were then used to produce microgreens. The germination index was higher in the seeds from Se-treated plants and the microgreens were enriched in Se. The antioxidant capacity of Se-fortified microgreens was higher compared to the control. CONCLUSION: The production of microgreens from Se-enriched seeds could comprise a good system for obtaining microgreens with a high nutritional value. Basil plants treated with Se could be used to produce both Se-fortified leaves and microgreens. © 2019 Society of Chemical Industry.

Effect of selenium enrichment on metabolism of tomato (Solanum lycopersicum) fruit during postharvest ripening.

BACKGROUND: Selenium (Se) enrichment of plants seems effective in enhancing the health-related properties of produce and in delaying plant senescence and fruit ripening. The current study investigated the effects of Se on tomato fruit ripening. Tomato (Solanum lycopersicum L.) plants were grown in hydroponics with different Se-enriched nutrient solutions. Se, as sodium selenate, was added at a rate of 0 mg L-1 (control), 1, and 1.5 mg L-1 . RESULTS: Selenium was absorbed by roots and translocated to leaves and fruit. Enrichment with Se did not significantly affect the qualitative parameters of fruit at commercial harvest; instead it delayed ripening by affecting specific ripening-related processes (respiration, ethylene production, color evolution) during postharvest. In the current experiment 100 g of tomato hydroponically grown with a 1.5 mg Se L-1 enriched solution provided a total of 23.7 µg Se. Selenium recommended daily intake is 60 µg for women and 70 µg for men; thus the daily consumption of 100 g of enriched tomato would not lead to Se toxicity but would provide a good Se diet supplementation. CONCLUSIONS: The cultivation of tomato plants in a Se-enriched solution appeared effective in producing tomato fruit with improved performance during storage and postharvest shelf life, and also with greater potential health-promoting properties. © 2018 Society of Chemical Industry.

Multiple Consequences Induced by Epidermally-Located Anthocyanins in Young, Mature and Senescent Leaves of Prunus.

Anthocyanic morphs are generally less efficient in terms of carbon gain, but, in turn, are more photoprotected than anthocyanin-less ones. To date, mature leaves of different morphs or leaves at different developmental stages within the same species have generally been compared, whereas there is a lack of knowledge regarding different stages of development of red vs. green leaves. Leaves (1-, 7-, and 13-week-old) of red- (RLP) and green-leafed (GLP) Prunus in terms of photosynthetic rate, carbon metabolism and photoprotective mechanisms were compared to test whether anthocyanin-equipped leaves perform better than anthocyanin-less leaves and whether photoprotection is the primary role of epidermally-located anthocyanins, using for the first time a recently-developed parameter of chlorophyll fluorescence (qPd). GLP leaves had a higher photosynthetic rate in 1- and 7-week-old leaves, but RLP leaves performed better at an early stage of senescence and had a longer leaf lifespan. Anthocyanins contributed to leaf photoprotection throughout the leaf development, but were tightly coordinated with carotenoids. Besides photoprotecting, we propose that epidermal anthocyanins may be principally synthetized to maintain an efficient carbon-sink strength in young and senescent leaves, thus extending the RLP leaf lifespan.

Selenium Enrichment of Horticultural Crops.

The ability of some crops to accumulate selenium (Se) is crucial for human nutrition and health. Selenium has been identified as a cofactor of the enzyme glutathione peroxidase, which is a catalyzer in the reduction of peroxides that can damage cells and tissues, and can act as an antioxidant. Plants are the first link in the food chain, which ends with humans. Increasing the Se quantity in plant products, including leafy and fruity vegetables, and fruit crops, without exceeding the toxic threshold, is thus a good way to increase animal and human Se intake, with positive effects on long-term health. In many Se-enriched plants, most Se is in its major organic form. Given that this form is more available to humans and more efficient in increasing the selenium content than inorganic forms, the consumption of Se-enriched plants appears to be beneficial. An antioxidant effect of Se has been detected in Se-enriched vegetables and fruit crops due to an improved antioxidative status and to a reduced biosynthesis of ethylene, which is the hormone with a primary role in plant senescence and fruit ripening. This thus highlights the possible positive effect of Se in preserving a longer shelf-life and longer-lasting quality.

Effects of salinity stress on carotenoids, anthocyanins, and color of diverse tomato genotypes.

One nonanthocyanin-accumulating (Ailsa Craig) and three anthocyanin-accumulating tomato genotypes (Anthocyanin fruit type, Atroviolaceum, and Sun Black) were analyzed to assess differences in their carotenoid and anthocyanin levels and color and to evaluate the effects of nutrient solutions with different salt concentrations on these parameters. The carotenoid content of control Atroviolaceum tomatoes was ca. 2-2.5-fold higher relative to the other two types, and the color of its puree could be visually distinguished from those of other genotypes. Salinity stress led in some cases to a 2-3-fold increase in the lycopene content. Saline treatment increased the accumulation of total anthocyanins in fruits of Sun Black (2-fold increase), while it reduced it in fruits of Anthocyanin (10-fold decrease). In general, the treatment increased the differences in color of different purees. These results indicate that salinity stress can lead to similar or higher increases in tomato carotenoids than those achieved by genetic engineering. In addition, these changes were accompanied by visually discernible color differences in tomato products. Our findings show the considerable potential of exploiting saline soils to obtain tomatoes with higher levels of secondary metabolites like carotenoids and anthocyanins.

Root zone sensors for irrigation management in intensive agriculture.

Crop irrigation uses more than 70% of the world's water, and thus, improving irrigation efficiency is decisive to sustain the food demand from a fast-growing world population. This objective may be accomplished by cultivating more water-efficient crop species and/or through the application of efficient irrigation systems, which includes the implementation of a suitable method for precise scheduling. At the farm level, irrigation is generally scheduled based on the grower's experience or on the determination of soil water balance (weather-based method). An alternative approach entails the measurement of soil water status. Expensive and sophisticated root zone sensors (RZS), such as neutron probes, are available for the use of soil and plant scientists, while cheap and practical devices are needed for irrigation management in commercial crops. The paper illustrates the main features of RZS' (for both soil moisture and salinity) marketed for the irrigation industry and discusses how such sensors may be integrated in a wireless network for computer-controlled irrigation and used for innovative irrigation strategies, such as deficit or dual-water irrigation. The paper also consider the main results of recent or current research works conducted by the authors in Tuscany (Italy) on the irrigation management of container-grown ornamental plants, which is an important agricultural sector in Italy.