Salinity stress is increasingly affecting plant crops, including vegetables. Strigolactones (SLs) are involved in modulating plant responses to osmotic stress. To unequivocally demonstrate the role of endogenous SLs under salt stress, we compared the responses of tomato plants silenced for the SL biosynthetic gene CCD7 (CAROTENOID CLEAVAGE DIOXYGENASE7) with the relative wild-type and tested the effect of the specific SL analogue enantiomer GR245DS in stressed plants. Salt application increased the substrate electrical conductivity and leaf and root Na+ concentration, and decreased stem water potential. Salinity also restrained growth, reduced stomatal conductance, increased content of leaf proline, and enhanced activity of ROS-scavenging enzymes. SL-depleted plants were more susceptible to stress, showing stronger reduction of shoot growth than wild-type plants, and lower leaf concentration of proline, K+ and Mg2+. Leaf MDA concentration was higher in SL-depleted plants. Stomatal conductance and leaf soluble sugar concentration under stress were not affected by genetic SL depletion, but they respectively decreased and increased in leaves treated with GR245DS. Activity of ROS-scavenging enzymes in leaves was also modulated by GR245DS treatment. Our results unambiguously demonstrate that endogenous SLs contribute to improving tolerance to salt stress in tomato by affecting differential accumulation of ions and organic solutes, as well as responses to oxidative stress.

Flavescence dorée (FD) is a phytoplasma disease transmitted by insects, causing severe damage in vineyards across Europe. Since there is no effective treatment, infected plants must be removed to prevent further spread. There is variation in susceptibility to FD among different grapevine cultivars, and some exhibit symptom remission, known as recovery, although the mechanisms behind this are unclear. Diseased plants accumulate soluble sugars, including sucrose, which influences the concentration of trehalose-6-phosphate (T6P), a signalling molecule affecting plant growth and stress responses. It is hypothesized that sucrose-mediated signalling via T6P could trigger defence mechanisms, reducing FD pathogen load and increasing plant recovery. To test this hypothesis, two grapevine genotypes with different susceptibility to FD were compared, revealing increased sucrose level and trehalose-6-phosphate synthase (TPS) activity in the more tolerant cultivar. However, FD-infected plants showed inhibited sucrose-cleaving enzymes and no activation of TPS expression. Attempts to enhance sucrose levels through trunk infusion and girdling promoted sucrose metabolism, T6P biosynthesis, and defence gene expression, facilitating symptom recovery. Girdling particularly enhanced T6P biosynthesis and expression of defence genes above the treatment point, reducing FD pathogen presence and promoting recovery. These findings indicate that elevated sucrose levels, possibly signalling through T6P, may limit FD pathogen spread, aiding in plant recovery.

Stress memory is an adaptive strategy for plants to cope with fluctuating environmental conditions. For example, it has been shown that the transcriptional responses to drought can be “trained”, i.e. changed, by a previous stress episode. Also, the so-called after-effect of drought is a feature of stress memory seen at the stomatal level: an incomplete recovery of conductance after drought, even when water potential has fully recovered. This effect has been shown to depend on the phytohormones abscisic acid and strigolactones, but whether and how repeated drought spells affect its intensity is unclear, as it is unclear how much of the “trainability” of physiological and molecular responses depends on strigolactones. This study investigated the contribution of strigolactones to physiological and transcriptional drought memory, by comparing the stomatal conductance and transcriptome of wild-type versus strigolactone-depleted tomato plants in repeated dehydration cycles. We found that the after-effect of drought can be primed by a previous drought episode; and, that strigolactones are indispensable for full priming. About half of the genes that display a drought memory profile require an intact strigolactone pathway for trainability. Several potential candidates are proposed as effectors of strigolactone-dependent drought memory, namely for enhanced abscisic acid sensitivity and antioxidant activities, and for the maintenance of cellular homeostasis via enhanced protein preservation under environmental duress. Our findings bear applicative implications for stress resilience improvement in crops and help to explain why plants treated with synthetic strigolactones display improved performances under a very diverse array of stresses.

This study aimed to clarify how microclimate diversity altered volatilomics in Cabernet Sauvignon grapes and wines. Four row-oriented vineyards were selected, and metabolites of grapes and wines were determined from separate canopy sides. Results showed that shaded sides received 59% of the solar radiation and experienced 55% of the high-temperature days compared to the exposed sides on average. Grape primary metabolites were slightly affected by the canopy side. Herbaceous aromas were consistently more abundant in grapes and wines from shaded clusters. Heat-stressed canopy sides accelerated terpenoid loss and increased norisoprenoid levels in grapes, while β-damascenone in north-side wines was 13%-32% higher than that in south-side wines of the east-west vineyard. The northeast-southwest vineyard showed the most notable variation in taste and aroma sensory scores, with four parameters significantly different. There were 32 aroma series identified in wines, and banana, pineapple, and strawberry odors were highly correlated with aroma sensory score.

A major issue in several farming areas of the Mediterranean basin consists of drought and salinity stress. This stress is mainly due to a steady exposition of warm daily temperature and heatwaves, moreover with inevitable irrigation with saline water. Therefore, detecting the stress is essential to minimise significant yield loss and preserve agricultural sustainability. In this context, remote and proximal sensing can play a crucial role in allowing fast, not destructive, extensive, and reliable assessment of crop status. In this work, the effectiveness of several multispectral indices in detecting salinity and water stress in tomato plants, grown under controlled green-house conditions, was investigated. Three different classifiers (fine tree model, linear discriminant model, and linear support vector machines model) were used to verify whether, and the extent to which, the adopted multispectral indices can be adopted to identify a stress condition of the tomato plants. In the experimental campaign, the stress occurrence on tomato plants was assessed on the base of a set of ecophysiological measurements, such as transpiration, stomatal conductance, and photosynthesis rate. Obtained results showed that a classification model based on linear support vector machines, exploiting the combination of Photochemical Reflectance Index and the Chlorophyl Index, can detect drought and salinity stress in tomato plants with an accuracy higher than 94%.

Phenolics are essential bioactive components that determine the appearance and taste characteristics of wines. The biosynthesis of grape phenolics is sensitive to vineyard microclimate conditions, which profoundly affects vineyard precision management. This study aimed to clarify the effect of partitioned harvesting based on vineyard canopy sides on grape and wine phenol levels. Parallel field experiments were conducted in four Cabernet Sauvignon vineyards with different row orientations across three seasons. Results showed that vineyard row orientation directly affected temperature-solar radiation distribution and spectrum in the cluster zone, ultimately affecting grape phenolics. Grape sugar content varied significantly in various canopy positions, which were associated with the photosynthetic capacity of grapevines. Partitioned harvesting significantly altered the distribution of anthocyanins and flavonols in grapes. Grapes and corresponding wines from exposed canopy sides showed higher flavonol concentrations than the shaded canopies, while anthocyanins varied, which were associated with temperature-solar radiation distribution around the cluster zone. Acylated anthocyanins and kaempferol-based flavonols showed high and significant correlations with the row orientations through regression models. The canopies with more heat stress produced wines with higher pH and lower anthocyanin levels. The different expressions of flavonoid pathway genes, such as VviPALs, VviC4Hs, VviCHIs, and VviFLSs were responsible for the anthocyanin-flavonol distribution patterns related to partitioned harvesting. The findings of this research provided a better understanding of vineyard precision management.

Strigolactones are a class of phytohormones with various functions in plant development, stress responses, and in the interaction with (micro)organisms in the rhizosphere. While their effects on vegetative development are well studied, little is known about their role in reproduction. We investigated the effects of genetic and chemical modification of strigolactone levels on the timing and intensity of flowering in tomato ( Solanum lycopersicum L.) and the molecular mechanisms underlying such effects. Results showed that strigolactone levels in the shoot, whether endogenous or exogenous, correlate inversely with the time of anthesis and directly with the number of flowers and the transcript levels of the florigen-encoding gene SINGLE FLOWER TRUSS ( SFT ) in the leaves. Transcript quantifications coupled with metabolite analyses demonstrated that strigolactones promote flowering in tomato by inducing the activation of the microRNA319- LANCEOLATE module in leaves. This, in turn, decreases gibberellin content and increases the transcription of SFT . Several other floral markers and morpho-anatomical features of developmental progression are induced in the apical meristems upon treatment with strigolactones, affecting floral transition and, more markedly, flower development. Thus, strigolactones promote meristem maturation and flower development via the induction of SFT both before and after floral transition, and their effects are blocked in plants expressing a miR319-resistant version of LANCEOLATE . Our study positions strigolactones in the context of the flowering regulation network in a model crop species.

Abiotic stresses, such as salinity, pose major risks on sustainability and productivity of most vegetable crops in the Mediterranean Basin. In soilless cultivation systems, mild salinity stress is introduced as a common practice to improve the organoleptic characteristics of tomato fruit, compromising at the same time crop production. In this study, we aimed to identify the impact of the salinity stress on the fruit quality of seven cherry-type tomato landraces (namely 'tomataki, 'GR-451/04, 'CC_1791 Allungato a Fiasco, Therry-INRAE (1), Therry-INRAE (2), 'Cherry-INRAE (3), Therry-INRAE (4)'). The experiment was conducted at the greenhouse facilities of the Laboratory of Vegetable Production at the Agricultural University of Athens. To apply the stress factor, the plants were grown under 30 mM NaC1 in the nutrient solution versus the non-saline treated plants that were irrigated with a nutrient solution containing 0.5 mM NaCI. Fruit quality parameters such as diameter, firmness, titratable acidity (TA) and total soluble solids content (TSSC) were assessed. According to the main findings of this study, no reduction in the fruit quality characteristics of the landraces Therry-INRAE (1), Therry-INRAE (2)' and 'Cherry-INRAE (3)' when exposed to salinity was observed. Salt stress improved the fruit firmness, TSSC and TA of the Greek landrace 'GR 451/04' while reduced its fruit diameter. On the contrary, increased salinity in the nutrient solution did not affect the diameter of fruit for landrace 'Cherry-INRAE-4, while led to increased concentrations of TSSC in fruit. The identified tolerant and resistant landraces could potentially be used in breeding programs to develop new cultivars and hybrids that can better adapt in saline-affected environments.

Salinity is a major stress factor that compromises vegetable production in semi-arid climates such as the Mediterranean. The accumulation of salts in the soil can be attributed to limited water availability, which can be exacerbated by changes in rainfall patterns and rising temperatures. These factors can alter soil moisture levels and evaporation rates, ultimately leading to an increase in soil salinity, and, concomitantly, the extent to which crop yield is affected by salinity stress is considered cultivar-dependent. In contrast to tomato hybrids, tomato landraces often exhibit greater genetic diversity and resilience to environmental stresses, constituting valuable resources for breeding programs seeking to introduce new tolerance mechanisms. Therefore, in the present study, we investigated the effects of mild salinity stress on the growth, yield, and nutritional status of sixteen Mediterranean tomato landraces of all size types that had been pre-selected as salinity tolerant in previous screening trials. The experiment was carried out in the greenhouse facilities of the Laboratory of Vegetable Production at the Agricultural University of Athens. To induce salinity stress, plants were grown hydroponically and irrigated with a nutrient solution containing NaCl at a concentration that could maintain the NaCl level in the root zone at 30 mM, while the non-salt-treated plants were irrigated with a nutrient solution containing 0.5 mM NaCl. Various plant growth parameters, including dry matter content and fruit yield (measured by the number and weight of fruits per plant), were evaluated to assess the impact of salinity stress. In addition, the nutritional status of the plants was assessed by determining the concentrations of macro- and micronutrients in the leaves, roots, and fruit of the plants. The key results of this study reveal that cherry-type tomato landraces exhibit the highest tolerance to salinity stress, as the landraces ‘Cherry-INRAE (1)’, ‘Cherry-INRAE (3)’, and ‘Cherry-INRAE (4)’ did not experience a decrease in yield when exposed to salinity stress. However, larger landraces such as ‘de Ramellet’ also exhibit mechanisms conferring tolerance to salinity, as their yield was not compromised by the stress applied. The identified tolerant and resistant varieties could potentially be used in breeding programs to develop new varieties and hybrids that are better adapted to salinity-affected environments. The identification and utilization of tomato varieties that are adapted to salinity stress is an important strategy for promoting agriculture sustainability, particularly in semi-arid regions where salinity stress is a major challenge.

Water shortage and heat driven evaporation in semi-arid climate, such as Mediterranean, that are mainly ascribed to climate change, introduced salinity as a major stress factor in vegetable crop production. Thus, the adaptation of vegetables, especially those susceptible to osmotic stress, is becoming more and more challenging to acquire sustainable cropping systems in saline environment. Unlike melon hybrids, melon landraces are less sensitive to environmental stresses and considered valuable sources of genetic characteristics for plant breeders' interest in breeding programs. This study was designed to assess the impact of salinity on several fruit quality characteristics of three melon landraces namely 'Tendra negro, 'Thrakiotiko' and 'Leyko Amyntaiou'. Both, the widely cultivated Spanish cultivar 'T111 (tipo piel de sapo)' and the commercial hybrid 'Lavigal' served as control. The experiment was carried out at the greenhouse facilities of the Laboratory of Vegetable Production at the Agricultural University of Athens. The different melon genotypes were hydroponically cultivated in an open hydroponic system with perlite as substrate, by applying a nutrient solution of 0.5 mM NaC1 to the non-saline treated plants and 30 mM NaC1 to the salt exposed plants. To investigate the impact of the salt stress on fruit quality, parameters such as the dry matter content, the pulp firmness, the values of color parameters L* a*, b*, hue angle and chroma and the titratable acidity were determined. The results showed that the color parameters and the pulp firmness were cultivar depended and were not affected by the salinity stress applied. Moreover, salinity stress resulted in increased dry matter content of the landrace 'Thrakiotiko, increased titratable acidity of the landrace 'Leyko Amyntaiou'. However, all tested parameters for the 'Tendra negro' landrace were not affected by the stress applied, indicating that this landrace could be a good candidate to be used in breeding programs for improving the tolerance of the commercial melon to salt stress.

The phytohormones strigolactones crosstalk with abscisic acid (ABA) in acclimation to osmotic stress, as ascertained in leaves. However, our knowledge about underground tissues is limited, and lacking in Arabidopsis: whether strigolactones affect ABA transport across plasma membranes has never been addressed. We evaluated the effect of strigolactones on the localization of ATP BINDING CASSETTE G25 (ABCG25), an ABA exporter in Arabidopsis thaliana. Wild-type, strigolactone-insensitive, and strigolactone-depleted seedlings expressing a green fluorescent protein:ABCG25 construct were treated with ABA or strigolactones, and green fluorescent protein was quantified by confocal microscopy in different subcellular compartments of epidermal root cells. We show that strigolactones promote the localization of an ABA transporter at the plasma membrane by enhancing its endosomal recycling. Genotypes altered in strigolactone synthesis or perception are not impaired in ABCG25 recycling promotion by ABA, which acts downstream or independent of strigolactones in this respect. Additionally, we confirm that osmotic stress decreases strigolactone synthesis in A. thaliana root cells, and that this decrease may support local ABA retention under low water availability by allowing ABCG25 internalization. Thus, we propose a new mechanism for ABA homeostasis regulation in the context of osmotic stress acclimation: the fine-tuning by strigolactones of ABCG25 localization in root cells.

Strigolactones (SLs) are carotenoid-derived phytohormones governing a wide range of physiological processes, including drought-associated stomatal closure. We have previously shown in tomato that SLs regulate the so-called after-effect of drought, whereby stomatal conductance is not completely restored for some time during recovery after a drought spell, irrespective of the water potential. To ease the elucidation of its molecular underpinnings, we investigated whether this SL effect is conserved in Arabidopsis thaliana by contrasting the physiological performances of the wild-type with SL-depleted (more axillary growth 4, max4) and insensitive (dwarf 14, d14) mutants in a drought and recovery protocol. Physiological analyses showed that SLs are important to achieve a complete after-effect in A. thaliana, while transcriptome results suggested that the SL-dependent modulation of drought responses extends to a large subset (about 4/5) of genes displaying memory transcription patterns. Among these, we show that the activation of over 30 genes related to abscisic acid metabolism and signaling strongly depends on SL signaling. Furthermore, by using promoter-enrichment tools, we identified putative cis- and trans-acting factors that may be important in the SL-dependent and SL-independent regulation of genes during drought and recovery. Finally, in order to test the accuracy of our bioinformatic prediction, we confirmed one of the most promising transcription factor candidates mediating SL signaling effects on transcriptional drought memory-BRI-EMS SUPPRESSOR1 (BES1). Our findings reveal that SLs are master regulators of Arabidopsis transcriptional memory upon drought and that this role is partially mediated by the BES1 transcription factor.

Strigolactones are phytohormones with many attributed roles in development, and more recently in responses to environmental stress. We will review evidence of the latter in the frame of the classic distinction among the three main stress acclimation strategies (i.e., avoidance, tolerance and escape), by taking osmotic stress in its several facets as a non-exclusive case study. The picture we will sketch is that of a hormonal family playing important roles in each of the mechanisms tested so far, and influencing as well the build-up of environmental memory through priming. Thus, strigolactones appear to be backstage operators rather than frontstage players, setting the tune of acclimation responses by fitting them to the plant individual history of stress experience.

The aim of this work was to evaluate the susceptibility to flavescence doree (FD) of 12 Vitis vinifera cultivars grown in Piedmont, and representative of the wine-making tradition of this area. The experiments were conducted under controlled conditions to ensure constant infection pressure. Test plants were ex vitro potted vines, singly inoculated with four Scaphoideus titanus infected by FD-C phytoplasma (FDp), under greenhouse conditions. Vines were tested for FDp at 5 and 8 weeks postinoculation (wpi) and the phytoplasma load was measured in leaves and roots at 8 wpi. Within the 14 V. vinifera accessions (belonging to 12 cultivars), three susceptibility clusters were identified. Cultivars within the low susceptibility group showed low phytoplasma loads and low percentages of infected plants, suggesting a tolerant behaviour. To confirm these results, four Vitis cultivars, representing extremes of FD susceptibility from low to high, were grafted onto Kober 5BB rootstocks and inoculated with laboratory-infected S. titanus, under semi-field conditions. The transmission experiments onto grafted cuttings confirmed that susceptibility to the disease depends on the scion genotype. The data indicated that none of the tested V. vinifera genotypes are resistant to FD, although some cultivars with low susceptibility are available, and can be explored for identifying genetic traits involved in disease tolerance/resistance. Moreover, ranking Vitis genotypes for their susceptibility to FD is in itself a valuable tool to support vine growers in their decision management, by helping them to choose the most appropriate varieties according to their specific FD epidemiological contexts.

The present work aims to analyse the influence of strigolactones on yield and agronomic WUE under drought. In order to investigate this issue, these parameters are being evaluated under well-watered and drought stress conditions, in self-grafted wild-type (M82) and strigolactone-depleted tomato plants (CCD7-silenced). Additionally, hetero-grafted plants (wild-type scions on strigolactone-depleted rootstocks, which leads to higher strigolactones in leaves) and self-grafted, strigolactone-treated wild-type plants are used to investigate the potentially positive effects of a moderate excess of hormone in the shoot on agronomic WUE and yield.

Trehalose-6-phosphate synthase (TPS) performs the first step in the biosynthetic pathway of trehalose-6-phosphate and trehalose. These two molecules play key roles in the control of carbon allocation and of stress responses in plants. We investigated the organization of the TPS gene family and its developmental and environmental expression regulation in grapevine, a major horticultural crop. We identified three novel genes in the family, and assessed the expression of the 11 family members in tissues and developmental phases. Two potentially biosynthetic TPS isoforms belonging to Class I were preferentially expressed in leaf (VvTPS1_A) and in fruit (VvTPS1_B) respectively. Sucrose treatment induced expression of VvTPS1_B, but not of VvTPS1_A, and a progressive decrease of sucrose concentration. Expression of a few Class II genes was affected by sucrose treatment. Application of osmotic stress by withdrawing irrigation also induced a decrease in sucrose and an increase of glucose content, and down-regulation of the VvTPS1_A gene. We discuss the possible role of these potential biosynthetic TPS genes. Subgroups of TPS genes, including both Class I and ClassII isoforms, followed a co-expression pattern in different conditions, suggesting that Class II TPS proteins may directly or indirectly interact with TPS biosynthetic genes. Our results pave the way for clarification of the role of TPS isoforms in grapevine responses to environmental stress.