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Implementing sustainable crop protection practices is crucial to protect global harvests and ensure high-quality food supplies. While priming is an established method in seed production for the fortification of plants against various stresses, it is not yet a standard practice in transplant cultivation. Thus, we evaluated the long-term effects of thermopriming—a heat-based priming technique—on the growth, development, and fruit yield of tomato plants. Following a recovery period of about six weeks for thermoprimed plants without stress inducers, we subjected them to subsequent salt stress to ascertain the persistence of the priming effects. Additionally, we compared the efficacy of thermopriming with benzothiadiazole (BTH), a chemical elicitor, in enhancing plant resilience to abiotic stress. While BTH application negatively impacted both plant growth and fruit health, thermopriming showed no such adverse effects on these parameters. Instead, thermopriming initially enhanced the plant defense mechanisms by increasing the accumulation of protective phenols and flavonoids in the leaves. Interestingly, while thermopriming did not alter the response to salt stress, it notably strengthened the overall resilience of the plants. Our findings underscore both the potential and temporal constraints of thermopriming memory. Nonetheless, primed plants exhibited temporarily increased stress tolerance, offering a means to safeguard the offspring. [ABSTRACT FROM AUTHOR]

Global plant production is challenged by unpredictable (a)biotic stresses that occur individually, simultaneously or staggered. Due to an increasing demand for environmentally friendly plant production, new sustainable, universal, and preventive measures in crop protection are needed. We postulate thermopriming as a suitable procedure that fulfills these requirements. Therefore, we performed thermopriming as a pre-conditioning on tomato transplants in combination with two subsequent salt stress treatments to evaluate their single and combined physiological effects on leaves and fruits with regard to plant performance, fruit yield and quality. We identified a cross-tolerance to salinity that was triggered by the preceding thermopriming treatment and resulted in an accumulation of phenols and flavonols in the leaves. Plant growth and fruit yield were initially delayed after the stress treatments but recovered later. In regard to fruit quality, we found an increase in carotenoid and starch contents in fruits due to thermopriming, while sugars and titratable acidity were not affected. Our results indicate that thermopriming can mitigate the impact of subsequent and recurrent stress events on plant performance and yield under production-like conditions. [ABSTRACT FROM AUTHOR]

Drought stress and nutrient deficiency are limiting factors in vegetable production that will have a decisive role due to the challenges of climate change in the future. The negative effects of these stressors on yield can be mitigated by crop grafting. The increasing demands for resource-use efficiency in crop production, therefore, require the development and phenotyping of more resilient rootstocks, and the selection of appropriate scions. We tested the effect of combined drought stress and nutrient deficiency on yield and fruit quality of the two tomato cultivars ‘Lyterno’ and ‘Tastery’ in the greenhouse, grafted onto different rootstock genotypes. The use of four different rootstocks, including two novel S. pennellii × S. lycopersicum hybrids and the proven-effective use of ‘Beaufort’, as well as self-grafted plants, allowed conclusions to be drawn about the differential stress mitigation of the rootstocks used. The stress-induced yield reduction of the scion ‘Lyterno’ can be mitigated more significantly by the novel hybrid rootstocks than by the commercial rootstock ‘Beaufort’. At the same time, however, the individual fruit weight and the lycopene content of the fruits were significantly reduced when grafted onto the hybrid rootstocks. In contrast, the cultivar ‘Tastery’ showed a weak stress response, so that a generally positive influence of the rootstocks independently of the scions could not be demonstrated. We conclude that, particularly for more sensitive cultivars, the selection of more resilient rootstocks offers the potential for sustainable and resource-efficient production not competing with the overall quality of tomatoes. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effect of red light irradiation during postharvest ripening with focus on the outer (epicarp and mesocarp) and inner (endocarp and seed) parts of tomatoes by evaluating concomitant alterations in bioactive compounds, such as lycopene, β-carotene, total phenolic and total flavonoid concentrations, external fruit color and spectral reflectance pattern, and the Simple Chlorophyll Fluorescence ratio. As promising measure, deriving from previous studies, green stage-1 tomatoes were harvested and treated daily with red light for 12 h per day, for 15 days (followed by storage in darkness for additional 6 days) or continuously radiated with red light for 21 days. Control untreated tomatoes were kept in the dark for the same period. Application of continous red light strongly accelerated changes in the outer layer of fruit, for example visible in color parameters. Significant differences between treatments were analyzed for major secondary metabolite compounds such as lycopene, β-carotene, total phenolic and total flavonoid in both outer and inner fruit layers. Continuous red light treatment led to the highest concentration of secondary metabolite compounds in all parameters. Therefore, it can be concluded that continuous red light radiation is the most effective treatment to accelerate the color development and ripening of the outer layer of the epicarp. Furthermore, it plays a role in stimulating the inner layer of the endocarp to provide beneficial secondary metabolite compounds. [ABSTRACT FROM AUTHOR]

In tomato production, the accruing green biomass shows promising potential as source of health-promoting compounds, such as rutin and solanesol, that are of high interest due to their medicinal properties. Naturally, they accumulate in plants growing in suboptimal growing conditions, e.g. influenced by biotic and abiotic stressors. With the aim to evaluate the potential use of tomato residues as source, we analyzed both leaf metabolites during a complete cultivation cycle, while applying single and combined stresses practically realized in greenhouse production. In the late season, contents of both metabolites were significantly enhanced by nutrient deficit in combination with 2 °C colder nights for 4 weeks and prolonged for in total 9 weeks. Particularly, higher solanesol contents were achieved by salt stress and elevated temperature after one week, even stronger when combined with drought. At harvest, stressed plants consist of less green biomass reducing the overall economic potential. However, practicable abiotic stresses should be considered as potential tool to induce the accumulation of beneficial compounds. Extracting profitable metabolites from the green biomass of the model crop tomato supports the overall goal to promote sustainable approaches in horticultural production. • Concomitant enhancement of both bioactive natural compounds rutin and solanesol in tomato leaves by single and combined abiotic stresses. • Identifying practicable and low-cost stressors suitable for operational processes in a commercial-like greenhouse in order to utilize metabolite-enriched plant biomass. • Monitoring of season-related and stress-induced accumulation of both metabolites during a complete cultivation cycle until tomato harvest in the scope of circular approaches in horticulture. • Assessing the impact of potentially 'positive' (eu)stress on plant's performance in order to improve horticultural products. [ABSTRACT FROM AUTHOR]

Highlights • Tomato residues are a natural source of rutin. • With supplemental intra-canopy LEDs, a higher content of rutin in tomato leaves was reached. • Non-destructive fluorescence parameters are suitable for detection of physiological changes in leaf compounds. • No correlation between FLAV and actual rutin content but strong clusters as influenced by leaf age and day of harvest. Abstract In modern tomato production, plant residues deliver an enormous amount of biomass including high-value components that so far are mainly unused. Especially the flavonol glycosid rutin has received stronger attention in recent research as a potentially health-promoting substance and due to its natural occurrence in tomato plants. In this study, tomato plants (cv. Lyterno) were grown in a commercial-like greenhouse and exposed to different lighting conditions. The objective of this work was to examine the influence of red (80%) and blue (20%) light-emitting-diodes (LEDs) (i) on rutin content in young and mature tomato leaves and (ii) on the physiological responses of tomato plants recorded with non-destructive sensor determinations. Our results revealed that supplementary LEDs induced the accumulation of secondary metabolites in tomato leaves grown in greenhouses such as higher rutin concentrations in young leaves and partly in mature leaves. A precise non-destructive estimation of rutin was not achieved but treatment-related differences in the fluorescence signals were clearly observed. Fluorescence-based recordings showed higher values for the Simple Fluorescence Ratio (SFR) as indicative of chlorophyll content, the Flavonol Index (FLAV) in young leaves and the Nitrogen Balance Index (NBI) in mature leaves. Even though a precise relationship between the FLAV index and the analytically determined rutin content could not be proven, clear clusters according to leaf age and day of leaf harvest were identified. [ABSTRACT FROM AUTHOR]

BACKGROUND: We examined the suitability of chlorophyll fluorescence‐based indices to monitor and predict concentrations of fruit maturity compounds during tomato ripening under different growing conditions in the greenhouse. The aim of this study was to evaluate the effects of chlorophyll concentration changes on fluorescence‐based indices and to exploit the relation between fluorescence and reflectance indices with the corresponding maturity compounds determined analytically. RESULTS: Fruits grown under water deficit matured faster than control fruits as recorded with fluorescence‐based indices. The SFR_R index correlated well with the analytical determination of chlorophyll content, whereas the single‐signal FRF_G correlated with lycopene content even if the sensor was unable to differentiate precisely between maturity stages 2 to 4. Neither the FLAV index nor the FLAV_UV index was suitable for flavonoid prediction in tomato fruits. Compared with fluorescence indices, the relation between the reflection index and pigment concentrations was lower for chlorophyll and higher for lycopene. CONCLUSION: Chlorophyll and lycopene content in tomato fruits can be estimated by means of fluorescence indices during the pre‐harvest phase. Since the chlorophyll decrease during tomato ripening is the driving force affecting all fluorescence signals, the methods are not reliable for estimation of other maturity compounds in tomato fruits. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Agricultural residues are natural sources for secondary metabolites as high value ingredients for industrial uses. The present work aims to exploit the accumulation potential of rutin and solanesol in tomato leaves following nitrogen and general mineral deficiency in a commercial-like greenhouse. Physiological responses of tomato plants were monitored non-destructively with a multiparametric fluorescence sensor, and biochemical parameters were determined by means of HPLC analysis. Nitrogen and general mineral limitation led to an accumulation of rutin in young tomato leaves while solanesol concentration was higher in mature leaves. In young leaves, the fluorescence indices SFR_R and NBI_G showed lower values compared to control plants for both stress treatments. On the contrary, FLAV and ANTH_RG values increased during the experiment, but no differences could be recorded in mature leaves. However, correlation analysis indicates, that the FLAV index is not a reliable tool to estimate the concentration of rutin and solanesol tomato leaves. To monitor fruit yield/quality as primary objective of tomato production, fruits showing symptoms of blossom end rot (BER) were counted before and after stress treatments. BER was determined more frequently for plants grown under a general mineral deficiency, concluding that a practical applicability at the end of fruit production is advisable. Our results indicate that by-products from Solanaceae plants are promising resources for valuable bioactive leaf compounds. To achieve the highest concentrations, the seasonal variation, the optimal environmental conditions, the concentrations in different plant organs and varieties as well as different production systems are of high interest for commercial implementation. [ABSTRACT FROM AUTHOR]

The convenient model Arabidopsis thaliana has allowed tremendous advances in plant genetics and physiology, in spite of only being a weed. It has also unveiled the main molecular networks governing, among others, abiotic stress responses. Through the use of the latest genomic tools, Arabidopsis research is nowadays being translated to agronomically interesting crop models such as tomato, but at a lagging pace. Knowledge transfer has been hindered by invariable differences in plant architecture and behaviour, as well as the divergent direct objectives of research in Arabidopsis vs. crops compromise transferability. In this sense, phenotype translation is still a very complex matter. Here, we point out the challenges of "translational phenotyping" in the case study of drought stress phenotyping in Arabidopsis and tomato. After briefly defining and describing drought stress and survival strategies, we compare drought stress protocols and phenotyping techniques most commonly used in the two species, and discuss their potential to gain insights, which are truly transferable between species. This review is intended to be a starting point for discussion about translational phenotyping approaches among plant scientists, and provides a useful compendium of methods and techniques used in modern phenotyping for this specific plant pair as a case study. [ABSTRACT FROM AUTHOR]