Introduction

In the Salento peninsula (southeastern Italy), Xylella fastidiosa (Xf) subsp. pauca is the cause of Olive Quick Decline Syndrome (OQDS). Approximately 85% of the olive trees in this region are made up of two cultivars, ‘Cellina di Nardò’ and ‘Ogliarola Salentina’, both of which are highly vulnerable to Xf. In heavily affected orchards, the sight of withered trees is common. However, certain potentially resistant genotypes stand out, either remaining asymptomatic or showing only mild symptoms.

Goals

The aim of this study is the definition of the performance features of a putatively resistant plant, SX32, which shares genetic traits with Tunisian cultivars like ‘Chemlali Sfax’ and ‘Sayali’, in an area with high Xf inoculum pressure.

Methodology

The symptoms and the bacterial count in SX32 were assessed and compared to the two cultivars ‘Cellina di Nardò’ (susceptible to Xf) and ‘Leccino’ (resistant to Xf), over the course of all four seasons. Disease severity was assessed using the pathometric scale described by Luvisi et al. (2017) (doi: 10.14601/Phytopathol_Mediterr-20578). Real-time PCR was performed following the protocol outlined by Harper et al. (2010) (doi:10.1094/PHYTO-06-10-0168), and bacterial concentration, expressed as CFU/mL, was determined based on the method described by D’Attoma et al. (2019) (doi:10.3390/pathogens8040272).

Results

The findings indicate that the canopy symptoms of SX32 are minimal, even fewer than those of ‘Leccino’, and show a constant pattern throughout the four seasons. It is noteworthy that ‘Cellina di Nardò’ shows an increasing trend, reaching its peak in autumn. In contrast, in relation to bacterial counts, SX32 falls between 10³ and 10⁶ CFU/mL, with the highest bacterial levels recorded in winter and the lowest in summer. ‘Cellina di Nardò’ exhibits a trend similar to that of SX32, but with a higher bacterial load, between 10⁴ and 10⁷ CFU/mL, whereas ‘Leccino’ shows the lowest bacterial count in winter and the highest in autumn, varying between 0 and 10⁷ CFU/ml.

Conclusions

SX32 demonstrates notable tolerance to Xf, exhibiting very low symptom levels, and it will be the subject of further study to explore additional sources of resistance to Xf. Although the higher bacterial count in SX32 compared to ‘Leccino’ was unexpected, it remains intriguing, as it might suggest the involvement of xylem endophytes that exert direct or indirect control over the pathogenic bacterium, helping the plant remain healthy despite the syndrome. Examples of such relationships, previously studied in olive trees, include associations with microorganisms like Burkholderia, Quambalaria, Phaffia, and Rhodotorula.

Introduction: Salinity and drought could be considered the most common environmental constraints in the Mediterranean area. Olive is a tree that is adapted to long dry periods and saline soil, but the degree of tolerance to these two adverse situations is cultivar-dependant. However, drought and salinity are two abiotic stresses that are increasingly present in the Mediterranean region, and identifying olive cultivars that can tolerate these adversities is a research priority.

Goals: As salinity and drought are limiting factors for olive production, the goals of this research were to detect consistent descriptors that could be used for underlying genotype-dependent performance under conditions of environmental disturbance that will occur in the future due to climate change, such as drought and salinity stress for olive plants.

Methodology: The multi-omics approach was used for screening olive cultivars that are well adapted to drought and salinity, including ‘Phenomic’, ‘Ionomic’, ‘Transcriptomic’ and ‘Metabolomic’ approaches. Using the ‘Phenomic’ approach, the physiological responses to the photosynthetic process in terms of gas exchange regulation and chlorophyll a fluorescence can be investigated. Moreover, visible symptoms of salt and drought stress, including foliar chlorosis and necrosis, reduced growth, and a general reduction in leaf area, can be monitored. Using the ‘Ionomic’ approach, the macro- and micro-element imbalance in all organs of olive trees were evaluated. Finally, the ‘Transcriptomic’ and ‘Metabolomic’ approaches were used to reveal the genes and metabolic pathways that are regulated in olives and determine their sensitivity or tolerance under drought and salinity conditions.

Conclusions: Considering recent research on olive under drought and salinity conditions, an overview of the principal mechanisms that olive plants adopt to overcome these two abiotic stresses is provided, examining anatomical, physiological, and metabolic traits. The selection of these traits could be used as a rapid olive screening method for selecting cultivars that can keep up with climate change without losing productivity.

Postharvest storage conditions significantly impact the polyphenolic composition and antioxidant stability of pears (Pyrus spp.), which are crucial for fruit quality, shelf life, and nutritional value. Polyphenols, including flavonoids and phenolic acids, contribute to the antioxidant potential of pears, but their stability varies under different storage conditions. This study investigated the effects of cold storage (4°C, 85% RH), controlled atmosphere (CA) storage (2% O₂ + 3% CO₂, 2°C), and ambient storage (25°C, 60% RH) on the polyphenolic profile and antioxidant activity of pear fruit over 0, 15, 30, and 60 days of storage. Polyphenols play a vital role in delaying senescence and enhancing fruit defense against oxidative stress. Previous studies indicate that low-temperature storage reduces enzymatic oxidation, while CA storage minimizes metabolic degradation, preserving polyphenol levels. However, ambient storage accelerates oxidative reactions, leading to significant degradation. Although such storage effects have been well-documented in apples and berries, limited research has explored these mechanisms in pears. In this study, polyphenols were quantified using high-performance liquid chromatography (HPLC), while antioxidant activity was evaluated through DPPH and ABTS assays. The enzymatic activity of polyphenol oxidase (PPO) and peroxidase (POD) was also measured to assess oxidative degradation. The results showed that CA storage best preserved polyphenol content, followed by cold storage, whereas ambient storage led to significant degradation (p < 0.05). Chlorogenic acid and quercetin derivatives exhibited the most substantial losses under ambient conditions. Antioxidant assays confirmed that pears stored in CA conditions maintained higher antioxidant activity, while enzymatic analysis indicated significantly lower PPO and POD activities under CA and cold storage, reducing oxidative damage. These findings suggest that CA storage effectively delays polyphenol degradation by reducing oxidative stress and enzymatic activity, thereby maintaining the antioxidant properties of pears. This supports the growing use of CA storage for prolonging fruit shelf life while preserving bioactive compounds. Future research should explore metabolomic and transcriptomic approaches to further elucidate the molecular regulation of polyphenol metabolism in pears during postharvest storage.

Tropical cropland systems will face challenges due to the expanding population and climatic changes. We used a temperature- and free-air-controlled enhancement and free-air carbon dioxide enrichment facility to analyze the effects of warming (+2ºC) and atmospheric CO2 (600 ppm) on Stylosanthes capitata (Vogel) parental plants' seed quality parameters. S. capitata is a Brazilian native forage legume and used in grazing systems. The plants were subjected to four treatments (with four replicates each): Control [C], increased CO2 [eCO2], warming [eT], and the combination [eCO2 + eT]. At the beginning of flowering, four parental plants per replicate were labeled and sampled 9-12 weeks after the first anthesis at the end of April 2015. For the seed quality evaluation, the parameters analyzed were as follows: the number of seeds per inflorescence (unit), 100-seed weights (mg), the percentage of abortions and unviable seeds (%), and the seed coat's color. For the seed germination evaluation, we assessed the seedling vigor and emergence. For the germination time (GT) and germination rate, seedling emergence on moistened Petri dishes was assessed daily until the ninth day, and germinability and the germination speed index (GSI) were calculated. Two-way and three-way ANOVAs were used to analyze treatment effects. Our results showed that warming increased the number of seeds per inflorescence by ~37%, reduced unviable seeds by 55%, and altered the seed coat color frequency to 64% beige with dots. Warming and eCO2 had opposite effects on seedling vigor, increasing it by 20% and decreasing it by 50%, respectively. The germination rate was influenced by the interaction of temperature and CO2, mainly from the second to fourth days and the last days, while treatments did not affect the GSI and germination time (GT). Overall, germination rates were around or above 90%. This study demonstrates that warming (+2 °C) and eCO2 (600 ppm) in the parental environment affect the reproductive and early survival strategies of S. capitata offspring. Our results provide a better understanding of the effects of simulated warming and elevated CO2 on the quality and germination dynamics of this important tropical species.

This work was supported by FAPESP (Grants 08/58075-8), FAPESP fellowships (Grant 15/23930-9 and 2013/18633-0), CNPq/ANA/MCTI (Grant 446357/2015-4), and CNPq fellowships (Grants 150737/2014-9 and 140144/2016-1).

Increased temperature (eT) and water stress (wS), alone and in combination, are among the factors that have the greatest influence on plant development and reproduction in the tropics. Using the T-FACE (Temperature Free-Air Controlled Enhancement) facility to increase canopy temperature integrated with a drip irrigation setup, under field conditions, we investigated the effects of water deficit and warming (+2 °C) on the pollen grains of Stylosanthes capitata, a leguminous species native to Brazil with significant economic and ecological importance. Plants were subjected to four treatments: aToW (ambient temperature with optimal water conditions), aTwS (ambient temperature with water stress), eToW (elevated temperature with optimal water conditions), and eTwS (elevated temperature combined with water stress). Flowers collected in the experiment were dehydrated in increasing ethanol series, pre-included in absolute ethanol and resin, and embedded in synthetic resin for pollen structure analysis within the flower's keel. Sections were cut with a Leica rotary microtome (2-4 microns) and stained with Toluidine Blue (TB) and Periodic Acid-Schiff (PAS). Histochemical staining included Alcian Blue, Sudan Black, Sudan III, Coomassie Blue, and Basic Fuchsin. PAS and PAS+TB reactions identified positive starch with Lugol's stain added. Analyses were conducted using a Nikon Microphot-FXA Fluorescence Light Microscope (LM). The results revealed a significant interaction between elevated temperature and water deficit on starch density within the pollen grains. As an immediate response to the imposed stresses, the starch within the pollen grain acts as an energy source to sustain pollen tube growth and facilitate successful fertilization. Moreover, the combination of these stresses led to the compaction of the intine in the pollen grain aperture region, which may hinder pollen tube germination and disrupt the reproductive processes of the species. These findings suggest that the physiological changes induced by water deficit, in combination with elevated temperature (+2 °C), can significantly impact the reproductive success of S. capitata.

This study was supported by FAPESP (Grant 08/58075-8), CNPq/ANA/MCTI (Grant 446357/2015-4), CNPq fellowship (Grants 141921/2019-6 and 304686/2022-0), and CAPES - Finance Code 001.

Resource efficiency is essential in today's approach to horticulture. The global problems of water scarcity, soil pollution, biodiversity loss, and rapid growth of the global population require increased food production with fewer resources. Resource efficiency is an index that allows us to define how much biomass an agri-food system is capable of producing per unit of the resource used. Closed hydroponic systems such as vertical towers (VHTs) have high resource use efficiency. In these systems, the water use efficiency (WUE) and the nutrient use efficiency (NUE) can be calculated in terms of the water lost through transpiration (T) and the concentration of the fertigation solution. The objective of this research was to determine the WUE and NUE for chard crops in VHT under greenhouse conditions and to evaluate its feasibility as an urban and peri-urban system for leafy vegetable production. The trials were carried out with chard in the late fall of 2024 in a tunnel-type greenhouse on the outskirts of the city of San Luis Potos. The VHTs were built with a 20 L square lower tank on which a cylindrical pipeline of 115 cm in diameter and 1.6 m in height was placed. Each pipe had 45 growing containers distributed on 15 levels of three containers spaced vertically 9 cm apart and a growing density of 25 plants·m^-2. The experimental design was completely randomized with three treatments (75, 100, and 125% of Steiner's universal nutrient solution) and three replications. The transpiration (T) of the crop (recording weight loss in the water tank) and the fresh weight (FW) of the plants (nine plants per VT) were measured daily using a precision scale. An ANOVA and Tukey's test for mean differentiation were performed with p < 0.05. Significant differences were found between treatments for FW, T, and WUE, obtaining the best results at 75% using Steiner's nutrient solution. These results are equal to or superior to those obtained in horizontal hydroponic systems or vertical farms reported to date. The data show water savings of more than 70% and up to a 30% reduction in the fertilizers used compared to the conventional agricultural systems of chard crops. Vertical hydroponic towers in greenhouses are an optimal horticultural production system that uses resources very efficiently, so their implementation is feasible in areas where water scarcity is critical or areas that are densely populated.

The increasing role of nanoparticles (NPs) in horticulture is transforming agricultural practices by enhancing plant growth, improving nutrient absorption, and enabling the precise delivery of agrochemicals. However, little is known about the use of NPs in the production of synthetic seeds, a propagation technique particularly valuable for seedless species. This research studied the impact of pure iron oxide nanoparticles (Fe₃O₄ NPs), citrate-stabilized iron oxide nanoparticles (Fe₃O₄CA NPs), and indole-3-acetic acid (IAA) on the genetic stability and metabolic activity of Chrysanthemum × morifolium (Ramat.) Hemsl. plants obtained from synthetic seeds. For this purpose, axillary buds of chrysanthemum ‘Richmond’ were embedded in 3% calcium alginate supplemented with NPs and IAA, either singularly or in combination. Next, the synthetic seeds were either stored at 4^oC in the dark (for eight weeks) or directly cultured in vitro on an agar–water medium at room temperature for 30 or 60 days. Next, the germinated seeds were transplanted to the greenhouse until the full flowering of the plants. The content of total polyphenols was determined in the leaves and inflorescences of the plants. Moreover, the content of anthocyanins was measured in the inflorescences. RAPD markers were used to assess the genetic stability of plants. It was found that NPs and IAA significantly affected the content of total polyphenols (TCPs) in the leaves of chrysanthemum. Most treatments stimulated the accumulation of these compounds but in a time-dependent manner. No decline in the value of this parameter was reported compared with the untreated control. Conversely, Fe₃O₄NPs and IAA + Fe₃O₄CA NPs stimulated the biosynthesis of polyphenols and anthocyanins in the inflorescences after 30 days of treatment; however, a decline in the content of these compounds was reported after 60 days in most experimental objects, except for Fe₃O₄CA NPs and IAA + Fe₃O₄CA NPs. RAPD analyses confirmed the genetic stability of the resulting plants. This study expands the knowledge on the application of nanoparticles in plant biotechnology.

The current trial investigated a low-cost leaf proximal sensor, known as ‘Fylloclip’, which detects the condensing water vapor resulting from the leaf transpiration process. This simple and inexpensive device enables an approximate evaluation of a plant's water status by comparing the daily patterns of leaf transpiration and solar radiation. In theory, when the plant is well hydrated, there is likely to be a strong correlation between condensation and sunlight. However, deviations from these patterns are indicative of a potential drop in the plant's hydration level. It is important to note that the sensor still requires validation with established parameters for assessing plants' water status. This study was conducted on one-year-old potted lemon trees grown in a greenhouse. Measurements included leaf transpiration (capacitance), stomatal conductance (g_s) assessed with a gas exchange analyzer, and climate data. Pearson correlation analysis was used to select relevant features, followed by a machine learning approach to develop a predictive model for g_s. The model incorporated capacitance data and other variables, including the leaf temperature, stem water potential, and air relative humidity. Among the tested models, Random Forest emerged as the most suitable, yielding an R² = 0.72 and a mean absolute error (MAE) = 13.53 between the observed and predicted g_s values. These results indicate that capacitance alone is insufficient for accurately predicting g_s. Integrating additional sensors, such as leaf temperature and relative humidity sensors, could improve the prediction accuracy. These preliminary results may serve as a starting point for developing models and algorithms to estimate plants' water status by correlating ‘Fylloclip’ output data with common indicators of plants' hydration status, such as the stem water potential and g_s. Moreover, this sensor may represent an affordable component of a Decision Support System (DSS) for efficient and sustainable irrigation management. The next step could be to test this sensor in an open field to obtain additional data supporting its validity.

Blackberries (Rubus fructicosus L.) are known as functional foods due to their rich concentration of bioactive compounds. Due to their limited shelf life and susceptibility to postharvest quality deterioration, it is imperative to investigate postharvest interventions that can prolong the fruit's quality. The aim of this research was to develop a sonicated and microwave-assisted pasteurized edible coating containing citrus peel essential oil (CPEO), and investigate its impact on the quality of blackberries stored at low and elevated temperatures through physico-chemical and antioxidant analysis. The coating effect on maintaining the quality of blackberries during storage was more prominent when it was applied on blanched blackberries. About 33.78% weight loss was observed in control blackberries (BB) after 21 days at 4ºC; blanched and coated blackberries indicated 18% reduction in fruit weight loss; and 65.11% reduction occurred in fruit decay. About 69.43% weight loss was recorded after 3 days in control blackberries stored at 30ºC. The pH of control blackberries increased by 9.36% whereas blanched and coated fruits indicated a 5.52% increase after 21 days. Blanched and coated blackberries indicated a 10.71% lower decrease in titerable acidity at 20ºC, whereas a 36.36% decline in acidity was observed in control blackberries stored at 30ºC. About 22.86% loss in TSS was observed in control blackberries after 21 days. The TSS/acidity ratio gradually increased during storage, reaching its maximum value (13.60) after 21 days in blanched and coated fruits. The sonicated edible coating reduced 23.65% loss in the total flavonoid and 24.50% loss in total flavanols compared to the uncoated fruits kept at 4ºC after 21 days. Blanched and coated samples displayed a 22.12% reduction in the loss of the total flavonoid at 20ºC and 17.30% at 30ºC and 18.05% reduced loss was obtained for the total flavanols at 20ºC and 15% at 30ºC. Blanched blackberries coated with a sonicated edible coating indicated a 16.91% reduction in the loss of total phenolic content and 27% TAA after 21 days. Blanched and coated blackberries indicated a 12.20% reduction in the loss of DPPH radical scavenging activity after 21 days at 4ºC. The sonicated edible coating comparatively maintained 19.59% DPPH radical scavenging activity compared to the control. The promising results concluded that sonicated edible coating is an innovative solution for effective postharvest quality during storage. However, additional work needs to be conducted to analyse the potential of sonicated edible coatings with different essential oils on different horticultural commodities at various storage temperatures.

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The identification of olive tree cultivars is essential to support agricultural sustainability, improve biodiversity conservation, and certify the traceability and the quality of olive oil. This is particularly important in regions such as Trás-os-Montes e Alto Douro in Portugal, where “Cobrançosa”, “Madural”, and “Verdeal de Trás-os-Montes” are predominant olive cultivars, being crucial in the agricultural economy, sustainability, and cultural heritage. As the world’s seventh largest producer of olive oil, Portugal depends on its olive-growing regions, with this region ranking as the second most important contributor to national production. Traditional methods for identifying olive cultivars rely on cataloging and using germplasm collections of cultivars and accessions, achieved through the application of both morphological and molecular markers. Nevertheless, these methods are laborious and time-consuming, limiting their scalability. Spectral reflectance analysis, using spectroscopic instruments to measure light interactions with plant surfaces at a specific wavelength, presents an efficient and reliable method for cultivar identification. In this study, spectral reflectance data from the leaves of “Cobrançosa”, “Madural”, and “Verdeal de Trás-os-Montes” olive tree cultivars were collected using a spectroradiometer (500–900 nm). To address the high dimensionality of the dataset, principal component analysis (PCA) was applied to retain essential information while reducing complexity, creating a dataset with 50 features and 432 samples (144 for each cultivar). Different machine learning algorithms—eXtreme Gradient Boosting (XGBoost), Random Forest (RF), Support Vector Classifier (SVC) and Decision Tree (DT)—were then trained to classify the olive tree cultivars, with XGBoost achieving the highest classification accuracy of 93.1%, while DT showed the lowest accuracy of 80%. The results also revealed a variation in the effectiveness of differentiating the three olive tree cultivars. The cultivar “Madural” demonstrated the highest F1-score (0.953), indicating clear spectral distinction from the others. In contrast, the cultivar “Cobrançosa” showed the least differentiation (F1-score of 0.918) due to a greater spectral overlap with the cultivar “Verdeal de Trás-os-Montes”. Thus, the results suggest the need for further refinement of the approach to address higher intra-class variability. This refinement would be particularly advantageous when incorporating new cultivars with spectral signatures that may increase interclass similarity. This study shows the potential of spectral reflectance and machine learning for precision agriculture. The results provide a methodology, even in preliminary stages, for applying spectroscopy to sustainable crop management. Future research could expand the dataset to include additional cultivars while exploring advanced machine learning techniques to further improve classification performance.