A metabolome and transcriptome survey to tap the dynamics of fruit prolonged shelf-life and improved quality within Greek tomato germplasm

IntroductionTomato is a high economic value crop worldwide with recognized nutritional properties and diverse postharvest potential. Nowadays, there is an emerging awareness about the exploitation and utilization of underutilized traditional germplasm in modern breeding programs. In this context, the existing diversity among Greek accessions in terms of their postharvest life and nutritional value remains largely unexplored.MethodsHerein, a detailed evaluation of 130 tomato Greek accessions for postharvest and nutritional characteristics was performed, using metabolomics and transcriptomics, leading to the selection of accessions with these interesting traits. ResultsThe results showed remarkable differences among tomato Greek accessions for overall ripening parameters (color, firmness) and weight loss. On the basis of their postharvest performance, a balance between short shelf life (SSL) and long shelf life (LSL) accessions was revealed. Metabolome analysis performed on 14 selected accessions with contrasting shelf-life potential identified a total of 206 phytonutrients and volatile compounds. In turn, transcriptome analysis in fruits from the best SSL and the best LSL accessions revealed remarkable differences in the expression profiles of transcripts involved in key metabolic pathways related to fruit quality and postharvest potential. DiscussionThe pathways towards cell wall synthesis, polyamine synthesis, ABA catabolism, and steroidal alkaloids synthesis were mostly induced in the LSL accession, whereas those related to ethylene biosynthesis, cell wall degradation, isoprenoids, phenylpropanoids, ascorbic acid and aroma (TomloxC) were stimulated in the SSL accession. Overall, these data would provide valuable insights into the molecular mechanism towards enhancing shelf-life and improving flavor and aroma of modern tomato cultivars

Effects of Genetic, Pre- and Post-Harvest Factors on Phenolic Content and Antioxidant Capacity of White Asparagus Spears

The effects of genetic, pre-harvest (season of harvest, spear diameter, spear portion and spear tip color) and post-harvest factors (storage and domestic preparation practices, e.g., peeling and cooking) on total phenolic, flavonoid and ascorbic acid content of white asparagus spears and their correlation with antioxidant capacity (DPPH and FRAP) were studied. Results showed that genetic material was important for the total phenolic content but not season of harvest, spear diameter or storage. Violet spear tips and apical spear portions showed the largest amount of total phenolics. Peeling did not affect total phenolics in fresh asparagus, whereas it reduced their content in stored asparagus, while cooking resulted in an increase in both fresh and stored asparagus. However, the soluble extract of total phenolics and flavonoids were minor and the missing significance of phenolics and flavonoids in antioxidant capacity of white asparagus spears depends on these small amounts

Atlas of phenotypic, genotypic and geographical diversity present in the European traditional tomato

[EN] The Mediterranean basin countries are considered secondary centres of tomato diversification. However, information on phenotypic and allelic variation of local tomato materials is still limited. Here we report on the evaluation of the largest traditional tomato collection, which includes 1499 accessions from Southern Europe. Analyses of 70 traits revealed a broad range of phenotypic variability with different distributions among countries, with the culinary end use within each country being the main driver of tomato diversification. Furthermore, eight main tomato types (phenoclusters) were defined by integrating phenotypic data, country of origin, and end use. Genome-wide association study (GWAS) meta-analyses identified associations in 211 loci, 159 of which were novel. The multidimensional integration of phenoclusters and the GWAS meta-analysis identified the molecular signatures for each traditional tomato type and indicated that signatures originated from differential combinations of loci, which in some cases converged in the same tomato phenotype. Our results provide a roadmap for studying and exploiting this untapped tomato diversity.We thank Universitat Illes Balears, the Greek Gene Bank (GGB-NAGREF), Universita degli Studi Mediterranea Reggio Calabria, the CRB-Leg (INRA-GAFL)", the Genebank of CNR-IBBR (Bari, Italy) and ARCA 2010 for seed sharing. CNR-IBBR also acknowledges the seed donors, the Leibniz Institute of Plant Genetics and Crop Plant Research, Maria Cristina Patane (CNR-IBE, Catania, Italy) and La Semiorto Sementi SRL, as well as Mrs. Roberta Nurcato for technical assistance. IBMCP-UPV acknowledges Maurizio Calduch (ALCALAX) for technical assistance and Mario Fon for English grammar editing. This work was supported by European Commission H2020 research and innovation program through TRADITOM grant agreement No.634561, G2P-SOL, grant agreement No. 677379, and HARNESSTOM grant agreement No. 101000716. Clara Pons and Mariola Plazas are grateful to Spanish Ministerio de Ciencia e Innovacion for postdoctoral grants FJCI-2016-29118 and IJC2019-039091I/AEI/10.13039/501100011033; Joan Casals to a Serra Hunter Fellow at Universitat Politècnica de Catalunya.Pons Puig, C.; Casals, J.; Palombieri, S.; Fontanet, L.; Riccini, A.; Rambla Nebot, JL.; Ruggiero, A.... (2022). Atlas of phenotypic, genotypic and geographical diversity present in the European traditional tomato. Horticulture Research. 9:1-16. https://doi.org/10.1093/hr/uhac112116

Advanced Greenhouse Horticulture: New Technologies and Cultivation Practices

Greenhouse horticulture is one of the most intensive agricultural systems, with the advantages of environmental parameter control (temperature, light, etc.), higher efficiency of resource utilization (water, fertilizers, etc.) and the use of advanced technologies (hydroponics, automation, etc.) for higher productivity, earliness, stability of production and better quality. On the other hand, climate change and the application of high inputs without suitable management could have negative impacts on the expansion of the greenhouse horticulture sector. This special issue gathers twelve papers: three reviews and nine of original research. There is one review that focuses on irrigation of greenhouse crops, while a second surveys the effects of biochar on container substrate properties and plant growth. A third review examines the impact of light quality on plant–microbe interactions, especially non-phototrophic organisms. The research papers report both the use of new technologies as well as advanced cultivation practices. In particular, new technologies are presented such as dye-sensitized solar cells for the glass cover of a greenhouse, automation for water and nitrogen deficit stress detection in soilless tomato crops based on spectral indices, light-emitting diode (LED) lighting and gibberellic acid supplementation on potted ornamentals, the integration of brewery wastewater treatment through anaerobic digestion with substrate-based soilless agriculture, and application of diatomaceous earth as a silica supplement on potted ornamentals. Research studies about cultivation practices are presented comparing different systems (organic-conventional, aeroponic-nutrient film technique (NFT)-substrate culture), quantitative criteria for determining the quality of grafted seedlings, and of wild species as alternative crops for cultivation

Impact of Light on Horticultural Crops

Light is an essential factor for the growth and quality of horticultural plants and its effects depend upon parameters such as duration, intensity and quality [...

Ascophyllum nodosum and Silicon-Based Biostimulants Differentially Affect the Physiology and Growth of Watermelon Transplants under Abiotic Stress Factors: The Case of Salinity

Salinization of cultivated soils is a global phenomenon mainly caused by agricultural practices and deteriorates plant production. Biostimulants are products which can be applied exogenously to enhance the plants’ defense mechanism and improve their developmental characteristics, also under abiotic stresses. We studied the potential of two biostimulants, Ascophyllum nodosum (Asc) seaweed and a silicon-based (Si), to alleviate the saline conditions endured by watermelon transplants. Three salinity (0 mM, 50 mM, and 100 mM NaCl) treatments were applied in watermelon seedlings transplanted in pots, while the two biostimulants were sprayed in the foliar in the beginning of the experiment. Relative water content was improved by Asc in the high salinity level. The plant area, leaf number, and shoot dry weight deteriorated in relation to the salinity level. However, the root system (total root length and surface area) was enhanced by 50 mM salt, as well as Asc in some cases. The OJIP transient of the photosynthetic apparatus was also evaluated. Some OJIP parameters diminished in the high salinity level after Asc application. It is concluded that after salt stress Asc provoked a positive phenotypic response, while Si did not alleviate the salinity stress of transplanted watermelon

Postharvest physiology and quality of fresh-cut rocket (Eruca sativa Mill.) and peach (Prunus persica L.)

A new category of horticultural products, this of fresh-cut fruit and vegetables has arisen the last years. During their processing, many physiological and biochemical alterations are noticed such as: a) increased ethylene and CO2 production, b) increased transpiration, c) membrane deterioration and d) secondary metabolite production, which lead to browning of the cut surfaces, yellowing, softening etc. and induce faster quality loss of the fresh-cut fruit compared to the intact ones. The purpose of this thesis was to study the postharvest physiology of fresh-cut rocket and peach and also to investigate the various factors that affect their quality. In particular, the factors that were studied in rocket were: a) the leaf age, b) the degree of wounding that was determined by the different leaf size, c) the storage temperature, d) the presence of ethylene in the storage environment, e) treatment with 1-MCP, f) treatment with 6-BA and g) the heat treatment. On the other hand, the factors that were studied in the peach were: a) the cultivar, b) the degree of wounding that was determined by the cutting and/or peeling, c) treatment with 1-MCP, d) treatment with various chemical compounds (citric acid, ascorbic acid, calcium chloride and oxalic acid) and e) heat treatment. The results showed that chlorophyll degradation was the most important postharvest alteration observed in fresh-cut rocket that resulted in leaf yellowing. During harvest, in young leaves the highest ethylene and CO2 production were recorded. In addition, they had more soluble solids content (SSC) and total soluble phenols but less nitrates compared to the fully expanded and mature leaves. During storage, in young leaves a significantly higher ethylene production was noticed, but not greater chlorophyll losses were observed after 10 days of storage at 10oC compared to the fully expanded and mature leaves. The degree of wounding, that was determined by the different leaf size (1 particle of 14 cm or 2 particles of 7 cm each or 4 particles of 3.5 cm each) had no effect on the CO2 and ethylene production during storage. After 14 days at 8oC in MAP, no differences between treatments were observed regarding color, chlorophyll content and chemical composition. Chlorophyll degradation in rocket leaves was prevented significantly during storage in low temperatures. Specifically, the shelf-life of the leaves that were stored at 0oC was 16 days, but it was reduced (3 days) in the leaves that were stored at 5oC. The quality of the leaves that were stored at 10oC was deteriorated very quickly (intense yellow colour) and their shelf-life was only 8 days. The ethylene presence (1 μl l-1) in the storage environment accelerated significantly the rocket yellowing compared to the leaves that were stored in air and reduced the shelf-life (at 10oC) from 10 to 8 days. Exposure of the leaves before storage to 1-MCP (0.5 μL L-1 for 4 hours at 10oC), limited the yellowing effect of the ethylene. Dipping of rocket leaves to a 6-BA solution (10 μl l-1) for 30 sec reduced the CO2 production (by 33%) and limited the chlorophyll deterioration (by 53%) compared to the control. In contrast, it had no significant effect on their chemical composition (SSC, ascorbic acid, nitrates, phenols and the total antioxidants). Heat treatment of leaves (dipping in water temperature of 50oC for 30 sec) reduced significantly the chlorophyll loss from 36% to 7%, after being stored in MAP at 8oC for 10 days. In addition, the heat treatment reduced the weight loss compared to the control from 3.4% to 2.2%, without affecting the chemical composition (SSC, ascorbic acid, nitrates, phenols and the total antioxidants).Τα νωπά τεμαχισμένα φρούτα και λαχανικά αποτελούν μια νέα κατηγορία οπωροκηπευτικών προϊόντων, κατά την προετοιμασία των οποίων παρατηρούνται πολλές φυσιολογικές και βιοχημικές μεταβολές, με κυριότερες την αυξημένη παραγωγή αιθυλενίου και διοξειδίου του άνθρακα (CO2), την αυξημένη διαπνοή, τη καταστροφή των μεμβρανών και την παραγωγή δευτερογενών μεταβολιτών, που προκαλούν καφέτιασμα στις επιφάνειες τομής, κιτρίνισμα, μαλάκωμα κ.ά. Άμεση συνέπεια των παραπάνω είναι η ταχύτερη υποβάθμιση της ποιότητάς τους, σε σχέση με τα ακέραια προϊόντα. Σκοπός της διατριβής ήταν η μελέτη της μετασυλλεκτικής φυσιολογίας των νωπών τεμαχισμένων προϊόντων ρόκας και ροδάκινου και η διερεύνηση της επίδρασης διαφόρων παραγόντων στην ποιότητά τους. Ειδικότερα, οι παράγοντες που μελετήθηκαν στη ρόκα ήταν η ηλικία των φύλλων κατά τη συγκομιδή, ο βαθμός τραυματισμού που καθορίστηκε από το διαφορετικό μέγεθος των τεμαχίων των φύλλων, η θερμοκρασία συντήρησης, η παρουσία αιθυλενίου στο περιβάλλον συντήρησης, το 1-MCP, η 6-BA και η θερμική μεταχείριση, ενώ στο ροδάκινο μελετήθηκαν η ποικιλία, ο βαθμός τραυματισμού που καθορίστηκε από το τεμαχισμό ή/και την αποφλοίωση, το 1-MCP, διάφορες χημικές ουσίες (κιτρικό οξύ, ασκορβικό οξύ, χλωριούχο ασβέστιο και οξαλικό οξύ) και η θερμική μεταχείριση. Τα αποτελέσματα έδειξαν ότι η σημαντικότερη μεταβολή που παρατηρήθηκε μετασυλλεκτικά στη νωπή τεμαχισμένη ρόκα ήταν η διάσπαση της χλωροφύλλης, που είχε ως αποτέλεσμα το κιτρίνισμα των φύλλων. Κατά τη συγκομιδή, παρατηρήθηκε ότι τα νεαρά φύλλα είχαν την υψηλότερη παραγωγή CO2 και αιθυλενίου, ενώ περιείχαν περισσότερα διαλυτά στερεά συστατικά (ΔΣΣ) και ολικές διαλυτές φαινόλες και λιγότερα νιτρικά από τα πλήρως ανεπτυγμένα και τα ώριμα φύλλα. Στη διάρκεια της συντήρησης καταγράφηκε σημαντικά υψηλότερη παραγωγή αιθυλενίου στα νεαρά φύλλα, χωρίς ωστόσο να παρατηρηθούν μεγαλύτερες απώλειες σε χλωροφύλλη μετά από συντήρηση 10 ημερών στους 10oC, σε σχέση με τα πλήρως ανεπτυγμένα και ώριμα φύλλα. Ο βαθμός τραυματισμού που καθορίστηκε από το διαφορετικό μέγεθος των τεμαχίων των φύλλων (ολόκληρο φύλλο των 14 cm ή δύο τεμάχια των 7 cm ή 4 των 3,5 cm) δεν επηρέασε την παραγωγή CO2 και αιθυλενίου κατά τη διάρκεια της συντήρησης στους 8οC για 14 ημέρες, ούτε το χρώμα, την περιεκτικότητα σε χλωροφύλλη και τη σύσταση (ΔΣΣ, ασκορβικό οξύ, νιτρικά, ολικές διαλυτές φαινόλες και συνολική αντιοξειδωτική ικανότητα μετά από 14 ημέρες στους 8oC σε συνθήκες τροποποιημένης ατμόσφαιρας (ΤΑ). Η διάσπαση της χλωροφύλλης των φύλλων επιβραδύνθηκε σημαντικά κατά τη συντήρηση στις χαμηλότερες θερμοκρασίες, με αποτέλεσμα μέγιστη διάρκεια ζωής στο ράφι στους 0oC να ανέρχεται στις 16 ημέρες, ενώ στους 5oC και 10oC τα αντίστοιχα διαστήματα ήταν 13 και 8 ημέρες. Η παρουσία αιθυλενίου (1 μl l-1) στο περιβάλλον συντήρησης (10oC) επιτάχυνε σημαντικά το κιτρίνισμα των φύλλων, μειώνοντας τη μέγιστη διάρκεια διατήρησης αποδεκτού χρώματος από 10 σε 8 ημέρες. Η έκθεση των φύλλων για 4 ώρες στους 10oC σε 0,5 μl l-1 1-MCP πριν τη συντήρηση, απέτρεψε το κιτρίνισμα που προκλήθηκε από την παρουσία του αιθυλενίου στο περιβάλλον συντήρησης. Η εμβάπτιση φύλλων σε υδατικό διάλυμα 10 μl l-1 6-BA για 30 sec μείωσε την παραγωγή CO2 κατά 33% και περιόρισε τη διάσπαση της χλωροφύλλης κατά 53% σε σχέση με το μάρτυρα, ενώ δεν επηρέασε σημαντικά τη σύστασή τους (ΔΣΣ, ασκορβικό οξύ, νιτρικά, ολικές διαλυτές φαινόλες και συνολική αντιοξειδωτική ικανότητα). Η θερμική μεταχείριση (εμβάπτιση των φύλλων σε νερό θερμοκρασίας 50oC για 30 sec) περιόρισε σημαντικά την απώλεια χλωροφύλλης από 36 σε 7%, μετά από συντήρηση σε ΤΑ στους 8oC για 10 ημέρες. Επιπλέον, η θερμική μεταχείριση μείωσε την απώλεια βάρους των φύλλων σε σχέση με το μάρτυρα από 3,4 σε 2,2%, χωρίς να επηρεάσει τη σύσταση (ΔΣΣ, ασκορβικό οξύ, νιτρικά, ολικές διαλυτές φαινόλες και συνολική αντιοξειδωτική ικανότητα)

<i>Ascophyllum nodosum</i> and Silicon-Based Biostimulants Differentially Affect the Physiology and Growth of Watermelon Transplants under Abiotic Stress Factors: The Case of Drought

Climate change is an inevitable process characterized by an abrupt increase in global temperature and a decrease in precipitations leading to drought incidents. Biostimulants could be a valuable tool for mitigating these harsh conditions. The objective of our study was to test the efficiency of two biostimulants, a silicon-based seaweed and the seaweed Ascophyllum nodosum, to mitigate the drought stress endured by watermelon transplants during the first few weeks after transplanting. In order to achieve this, three water treatments (100%, 75%, and 50% of field capacity) were applied in pots. Important growth parameters (leaf number, fresh weight, and plant area) deteriorated depending on water availability. This was also the case for the root system development displayed by root dry weight, total length, and surface area. It is the first time the OJIP transient has been evaluated after the application of A. nodosum for drought-stressed plants. Chlorophyll fluorescence parameters showed that the photosynthetic apparatus was more stressed when A. nodosum was applied, especially in the harshest conditions (i.e., 50% field capacity). Overall, the silicon-based biostimulant failed to demonstrate drought-mitigating potential compared to the non-treated counterparts. On the other hand, A. nodosum alleviated the negative effects of water deficit, especially in the harshest conditions

The Use of High-Quality Watermelon Seedlings Is Prerequisite to Limit the Transplanting Shock and Achieve Yield Earliness

One of the most important crops of the Mediterranean, watermelon (Citrullus lanatus), is almost exclusively established through seedlings. For many years, agronomists, nurseries, and farmers have aimed to produce and use high-quality seedlings for better growth in the field. However, seedling quality has not been examined as to what defines the subsequent plant, flower, and fruit development, and to what extent. Our aim was to test whether different seedling qualities labeled as “Optimum”, “Acceptable”, or “Not Acceptable” for cultivation actually perform variably in terms of vegetative, flowering, and fruit development, as well as fruit quality after a full growing cycle in the field. Vegetative growth (stem diameter, plant area, and leaf number) was evaluated until flowering and was enhanced for Optimum plants. The flowering of Not Acceptable plants started two days later, while Optimum plants retained a greater number of female flowers throughout the two-week blooming evaluation. Most importantly, Optimum plants developed mature fruits four and six days faster than the Acceptable and Not Acceptable ones, respectively, showing considerable yield earliness. The photosynthetic mechanism, as well as fruit morphology and phytochemical content, were not affected by quality categories. Overall, indeed it is important to use high-quality seedlings to achieve yield earliness of watermelon fruits

Influence of Light Spectra from LEDs and Scion × Rootstock Genotype Combinations on the Quality of Grafted Watermelon Seedlings

Grafting is the main means of propagation for watermelon crops. The aim of the present study was to evaluate whether light quality during graft healing variably affects different scion × rootstock genotype combinations. Two watermelon hybrid scions (Sunny Florida F1 and Celine F1) and two interspecific squash rootstocks (Radik and TZ-148) were used, and four scion × rootstock genotype combinations derived. After grafting, we tested seven light-emitting diodes (LEDs), which provided narrow-band red (R) and blue (B); R-B with 36% (36B), 24% (24B), and 12% (12B) blue; 12B with additional far-red (12B+FR); and white (W), in a healing chamber. In three genotype combinations, shoot length, leaf area, and shoot biomass were mainly enhanced under red-blue LEDs, while stem diameter was greater under R. In contrast, dry weight of roots, Dickson’s quality index, and ratio of shoot dry weight/length were variably affected in each genotype combination. From the results, it is concluded that light treatments differentially affected each genotype combination, but some parameters involving biomass production show genotypic dependency