Search Results (914)

The extensive use of pesticides has significant implications for public health and the environment. Breeding crop plants is the most effective and environmentally friendly approach to improve the plants’ resistance. However, it is time-consuming and costly, and it is sometimes difficult to achieve satisfactory results. Plants induce defense responses to natural elicitors by interpreting multiple genes that encode proteins, including enzymes, secondary metabolites, and pathogenesis-related (PR) proteins. These responses characterize systemic acquired resistance. Humic substances trigger positive local and systemic physiological responses through a complex network of hormone-like signaling pathways and can be used to induce biotic and abiotic stress resistance. This study aimed to assess the effect of humic substances on the activity of phenylalanine ammonia-lyase (PAL), peroxidase (POX), and β-1,3-glucanase (GLU) used as a resistance marker in various plant species, including orange, coffee, sugarcane, soybeans, maize, and tomato. Seedlings were treated with a dilute aqueous suspension of humic substances (4 mM C L⁻¹) as a foliar spray or left untreated (control). Leaf tissues were collected for enzyme assessment two days later. Humic substances significantly promoted the systemic acquired resistance marker activities compared to the control in all independent assays. Overall, all enzymes studied in this work, PAL, GLUC, and POX, showed an increase in activity by 133%, 181%, and 149%, respectively. Among the crops studied, citrus and coffee achieved the highest activity increase in all enzymes, except for POX in coffee, which showed a decrease of 29% compared to the control. GLUC exhibited the highest response to HS treatment, the enzyme most prominently involved in increasing enzymatic activity in all crops. Plants can improve their resistance to pathogens through the exogenous application of HSs as this promotes the activity of enzymes related to plant resistance. Finally, we consider the potential use of humic substances as a natural chemical priming agent to boost plant resistance in agriculture Full article

Land use conversion to perennial cropland often degrades the soil structure and fertility, particularly under Mediterranean climatic conditions. This study assessed spatial and temporal dynamics of soil properties and tree responses to 3-year repeated mature compost additions in a citrus orchard. Digital soil mapping revealed strong baseline heterogeneity in texture, CEC, and Si pools. Compost application markedly increased total organic C and N levels, aggregate stability, and pH with noticeable changes after the first amendment, whereas a limited C storage potential was found following further additions. NDVI values of tree canopies monitored over a 3-year period showed significant time-dependent changes not correlated with the soil fertility variables, thus suggesting that multiple interrelated factors affect plant responses. The non-crystalline amorphous Si/total amorphous Si (_iSi:Si_amor) ratio is here proposed as a novel indicator of pedogenic alteration in disturbed agroecosystems. These findings highlight the importance of tailoring organic farming strategies to site-specific conditions and reinforce the value to combine C and Si pool analysis for long-term soil fertility assessment. Full article

Manganese (Mn) excess and low pH often coexist in some citrus orchard soils. Little information is known about the underlying mechanism by which raising pH reduces Mn toxicity in citrus plants. ‘Sour pummelo’ (Citrus grandis (L.) Osbeck) seedlings were treated with 2 (Mn2) or 500 (Mn500) μM Mn at a pH of 3 (P3) or 5 (P5) for 25 weeks. Raising pH mitigated Mn500-induced increases in Mn, iron, copper, and zinc concentrations in roots, stems, and leaves, as well as nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, copper, iron, and zinc distributions in roots, but it mitigated Mn500-induced decreases in nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, and boron concentrations in roots, stems, and leaves, as well as nutrient imbalance. Raising pH mitigated Mn500-induced necrotic spots on old leaves, yellowing of young leaves, decreases in seedling growth, leaf chlorophyll concentration, and CO₂ assimilation (A_CO2), increase in root dry weight (DW)/shoot DW, and alterations of leaf chlorophyll a fluorescence (OJIP) transients and related indexes. Further analysis indicated that raising pH ameliorated Mn500-induced impairment of nutrient homeostasis, leaf thylakoid structure by iron deficiency and competition of Mn with magnesium, and photosynthetic electron transport chain (PETC), thereby reducing Mn500-induced declines in A_CO2 and subsequent seedling growth. These results validated the hypothesis that raising pH reduced Mn toxicity in ‘Sour pummelo’ seedlings by (a) reducing Mn uptake, (b) efficient maintenance of nutrient homeostasis under Mn stress, (c) reducing Mn excess-induced impairment of thylakoid structure and PEPC and inhibition of chlorophyll biosynthesis, and (d) increasing A_CO2 and subsequent seedling growth under Mn excess. Full article

Optimizing irrigation and the targeted use of plant growth regulators are key strategies to improve productivity in citrus systems under water-limited conditions. This study evaluated the effects of three irrigation levels (4.44, 5.18, and 7.77 mm day⁻¹) combined with variable doses of naphthaleneacetic acid (NAA) and gibberellic acid (GA₃) on physiological and productive responses in Citrus aurantiifolia. The treatment with 7.77 mm irrigation and moderate doses of NAA (100 mg L⁻¹) and GA₃ (80 mg L⁻¹) increased yield by 38% (6.2 kg/plant), and it enhanced photosystem II photochemical efficiency (F_v/F_m = 0.82), chlorophyll index (SPAD = 62), and fruit weight by 15%. In contrast, high hormone doses under water deficit reduced leaf water potential and impaired physiological performance, leading to lower productivity. These findings support the combined use of regulated deficit irrigation and hormonal biostimulation as a sustainable strategy to enhance key lime yield and resource efficiency in semi-arid environments. Full article

In recent years, low temperature has seriously threatened the citrus industry. Arbuscular mycorrhizal fungi (AMF) can enhance the absorption of nutrients and water and tolerance to abiotic stresses. In this study, pot experiments were conducted to study the effects of low-temperature stress on citrus (trifoliate orange, Poncirus trifoliata L. Raf.) with AMF (Diversispora epigaea D.e). The results showed that AMF inoculation significantly increased plant growth, chlorophyll fluorescence, and photosynthetic parameters. Compared with 25 °C, −5 °C significantly increased the relative conductance rate and the contents of malondialdehyde, hydrogen peroxide, soluble sugar soluble protein, and proline, and also enhanced the activities of catalase and superoxide dismutase, but dramatically reduced photosynthetic parameters. Compared with the non-AMF group, AMF significantly increased the maximum light quantum efficiency and steady-state light quantum efficiency at 25 °C (by 16.67% and 61.54%), and increased the same parameters by 71.43% and 140% at −5 °C. AMF also significantly increased the leaf net photosynthetic rate and transpiration rate at 25 °C (by 54.76% and 29.23%), and increased the same parameters by 72.97% and 26.67% at −5 °C. Compared with the non-AMF treatment, the AMF treatment significantly reduced malondialdehyde and hydrogen peroxide content at 25 °C (by 46.55% and 41.29%), and reduced them by 28.21% and 29.29% at −5 °C. In addition, AMF significantly increased the contents of soluble sugar, soluble protein, and proline at 25 °C (by 15.22%, 34.38%, and 11.38%), but these increased by only 9.64%, 0.47%, and 6.09% at −5 °C. Furthermore, AMF increased the activities of superoxide dismutase and catalase at 25 °C (by 13.33% and 13.72%), but these increased by only 5.51% and 13.46% at −5 °C. In conclusion, AMF can promote the growth of the aboveground and underground parts of trifoliate orange seedlings and enhance their resistance to low temperature via photosynthesis, osmoregulatory substances, and their antioxidant system. Full article

The Citrus tristeza virus (CTV), a member of the Closterovirus genus, is considered a serious threat to citrus trees grafted onto sour orange (SO) rootstock. In the Mediterranean area, the most prevalent CTV strains are VT and T30. The VT strain includes both mild and severe isolates, some of them associated with seedling yellows (SY) syndrome. Mild CTV-VT isolates that do not induce SY symptoms (no-SY) show minor variations in their Orf1a, p23, and p33 genes, with a single nucleotide polymorphism at position 161 of the p23 gene. These isolates can repress superinfection with homologous severe isolates. The aim of this study was to investigate the mechanism of cross-protection by means of biological indexing, real-time RT-PCR high-resolution melting (HRM), and p23 gene amplicon sequencing. Four no-SY CTV-VT isolates were inoculated onto SO seedlings and Hamlin sweet orange trees grafted on SO. These plants were later challenged with two homologous CTV-VT SY isolates and remained asymptomatic. The biological evaluation of the infection process in superinfected plants was investigated via inoculation of the bark on SO seedlings that were also asymptomatic. A parallel HRM analysis of midvein RNA extracts revealed that the melting temperature (Tm) of the no-SY isolates was statistically lower than that of the SY isolates. The Tm values of RNAs extracts from superinfected plants were not statistically different from those of the no-SY isolates. This suggests that the SY isolates failed to establish infection or replicate in plants pre-inoculated with no-SY isolates. This blockage of replication resembles superinfection exclusion, with attractive perspectives to prevent SY damage in field applications. Full article

Gamma-aminobutyric acid (GABA), a ubiquitous non-protein amino acid, plays a vital role in the response of plants to biotic and abiotic stresses. This review summarizes the underlying mechanisms through which GABA contributes to plant stress resistance, including its biosynthetic and metabolic pathways, as well as its regulatory roles in enhancing stress tolerance and improving fruit quality. In plants, GABA is primarily synthesized from glutamate by the enzyme glutamate decarboxylase (GAD) and further metabolized by GABA transaminase (GABA-T) and succinic semialdehyde dehydrogenase (SSADH). The accumulation of GABA regulates various physiological and biochemical processes, including the control of stomatal closure, enhancement of antioxidant capacity, maintenance of ionic homeostasis, and stabilization of cellular pH. Moreover, GABA interacts with phytohormones to regulate plant growth, development, and stress tolerance. Notably, increasing GAD expression through genetic engineering has been shown to enhance tolerance to stresses, such as drought, saline-alkali, cold, and heat, in various plants, including tomato, rice, and creeping bentgrass. Additionally, GABA has effectively improved the storage quality of various fruits, including citrus fruits, apples, and strawberries. In conclusion, GABA holds significant research potential and promising applications in agricultural production and plant science. Full article

Urolithiasis (UL) is the presence of stones in the kidneys or urinary tract; its prevalence has increased worldwide. Thus, strategies have been sought to reduce it and one of them is the use of medicinal plants due to their accessibility, low cost, and cultural traditions. Studies on traditional medicinal plants in UL mainly documented results of litholytic and urinary parameters. Although, stone formation is related to oxidative stress and inflammation, and only a few studies are focused on these types of biomarkers. Thus, the aim of the present review was to summarize studies showing the antioxidant and anti-inflammatory effects of traditional medicinal plants used in UL management. We performed a scoping review; the database sources used were MEDLINE/PubMed, Google Scholar, SpringerLink, Scielo and Redalyc. From a total of 184 studies screened, six were included from China (2), India (3), and Corea (1). These studies have shown the antioxidant and anti-inflammatory effects of traditional medicinal plants, including Glechoma longituba (G. longituba), Bergenia ligulate (B. ligulate), Lygodium japonicum (L. japonicum), Citrus limon (C. limon), Xanthium strumarium (X. strumarium) and Tribulus terrestris (T. terrestris). They have also described their molecular mechanism of antioxidant and anti-inflammatory effects through the activation of antioxidant genes induced by Nrf2 or by suppressing the inflammatory gene expression by the inhibition of NFκ-B. These effects could be modulated by their bioactive compounds, such as polyphenols, flavonoids, tannins, saponins, and terpenes, present in these plants. This review summarizes the antioxidant and anti-inflammatory effects of traditional medicinal plants and highlights their molecular mechanisms of action and main bioactive compounds. This evidence may be used in biotechnology and synthetic biology areas for the development of new products from plant-derived compounds to reduce the high recurrence rates of UL. Full article

Plants produce an extensive repertoire of secondary metabolites, developed over evolutionary time to support survival. Among these, D-limonene, a monoterpene exuded by citrus fruits, has demonstrated a broad range of pharmacological activities. This review elucidates limonene’s biological versatility, spanning antioxidant, anti-inflammatory, antitumor, antidiabetic, neuroprotective, and gastroprotective domains. Synthesizing data from both preclinical and early-phase clinical research, we explore its molecular mechanisms, ranging from reactive oxygen species mitigation and apoptosis induction to metabolic remodeling and neurotransmitter modulation. Special attention is given to limonene’s emerging role in oncological therapeutics, notably in breast and liver cancers, and its capacity to ameliorate pathophysiological hallmarks of diabetes and neurodegeneration. Its low toxicity and high bioavailability support its potential as a safe adjunct or alternative in phytotherapy. This review advocates for continued investigation into limonene’s translational potential across a spectrum of neoplastic and non-neoplastic diseases. Full article

Background: Contemporary agriculture heavily relies on synthetic chemicals to ensure high yields and food security; however, their overuse has led to health issues and the development of pesticide resistance in pests. Researchers are now exploring natural, eco-friendly alternatives for pest control. Methods: This study evaluated two ethanol-based formulations (1.25% and 2.50%, v/v) derived from the tangerine peel (Citrus reticulata L. var. Clementina) against conventional chemical treatments and an untreated control group in the cultivation of potatoes (Solanum tuberosum L. var. Capiro). A randomised block design was used, with three blocks per treatment containing 45 plants. The experiment was conducted during the wet season (February–April 2023). Results: According to visual inspections and yellow traps, following weekly application from days 30 to 105 post-planting to monitor pest (e.g., Frankliniella occidentalis, Aphididae) and beneficial insect (e.g., Coccinellidae, Apis mellifera) populations, the 2.50% formulation performed similarly to chemical treatments against pests, whilst being harmless to beneficial insects. Post-harvest analysis showed that the formulations achieved 73% of conventional yields, with comparable tuber damage and levels of Premnotrypes vorax larvae. Conclusions: Toxicological tests confirmed the eco-friendliness of the formulations, making them suitable for small-scale Andean ‘chakras’ in organic farming and honey production, without the use of chemicals. Full article

Background: GRAS transcription factors are crucial for plant development and stress responses but remain poorly characterized in citrus. Soil salinization increasingly threatens sweet orange (Citrus sinensis) yield. Identifying salt-responsive GRAS genes could reveal key tolerance determinants for breeding resistant cultivars. Methods: We systematically identified and analyzed sweet orange GRAS transcription factors using bioinformatics. Results: Forty-three CsGRAS genes were identified, phylogenetically classified into ten subfamilies, and found to be structurally conserved. A promoter analysis revealed a high prevalence (58.78%) of hormone- and stress-responsive cis-elements. These genes reside on nine chromosomes, with segmental duplication being the primary evolutionary driver (eight duplicated pairs). Functional enrichment implicated hormone signaling pathways in regulating growth under stress. Transcriptome profiling identified 42 differentially expressed CsGRAS genes (19 upregulated and 23 downregulated) under salt stress. qRT-PCR validated the expression patterns of selected genes (e.g., CsGRAS15 and CsGRAS27). Notably, DELLA subfamily members CsGRAS15 and CsGRAS27, key negative regulators in gibberellin (GA) signaling, were differentially expressed. Modulating these DELLA proteins presents a promising strategy to enhance sweet orange salt tolerance by mitigating GA-mediated growth inhibition during stress. Conclusion: This study identifies salt-responsive CsGRAS genes, highlighting CsGRAS15 and CsGRAS27 as potential targets for improving salt tolerance in citrus. Full article

The use of unmanned aerial vehicle (UAV) pesticide spraying technology in precision agriculture is becoming increasingly important. However, traditional spraying methods struggle to address the precision application need caused by the canopy differences of fruit trees in orchards. This study proposes a UAV orchard variable-rate spraying method based on canopy volume. A DJI M300 drone equipped with LiDAR was used to capture high-precision 3D point cloud data of tree canopies. An improved progressive TIN densification (IPTD) filtering algorithm and a region-growing algorithm were applied to segment the point cloud of fruit trees, construct a canopy volume-based classification model, and generate a differentiated prescription map for spraying. A distributed multi-point spraying strategy was employed to optimize droplet deposition performance. Field experiments were conducted in a citrus (Citrus reticulata Blanco) orchard (73 trees) and a litchi (Litchi chinensis Sonn.) orchard (82 trees). Data analysis showed that variable-rate treatment in the litchi area achieved a maximum canopy coverage of 14.47% for large canopies, reducing ground deposition by 90.4% compared to the continuous spraying treatment; variable-rate treatment in the citrus area reached a maximum coverage of 9.68%, with ground deposition reduced by approximately 64.1% compared to the continuous spraying treatment. By matching spray volume to canopy demand, variable-rate spraying significantly improved droplet deposition targeting, validating the feasibility of the proposed method in reducing pesticide waste and environmental pollution and providing a scalable technical path for precision plant protection in orchards. Full article

Lemon basil (Ocimum × citriodorum) is a highly valued aromatic plant renowned for its distinct citrus aroma. This study aimed to evaluate sustainable substrates and cultivation systems for its production. Two complementary and sequential experiments were conducted: an initial experiment designed to compare coconut fiber mixed in varying proportions with perlite to rock wool, evaluating their effectiveness during germination and early growth (experiment 1), and a subsequent experiment aimed at assessing plant performance in a decoupled aquaponic system relative to hydroponics utilizing the best-performing coconut fiber-perlite mixture from the first phase along with rock wool as substrates (experiment 2). The substrate with 70% coconut fiber and 30% perlite (F70:P30) significantly improved seed germination, leaf number, and total leaf area of seedlings. The decoupled aquaponic cultivation system resulted in a 52.5% increase in flavonoid content, accompanied by higher calcium and magnesium uptake in stems and roots compared to hydroponics. These findings clearly underscore the potential of coconut fiber substrates mixed with perlite as sustainable alternatives to rock wool, reducing environmental impact, disposal costs, and health risks. Similarly, aquaponic cultivation emerges as a valuable strategy for sustainable lemon basil (Ocimum × citriodorum) production, offering comparable yields to hydroponics while improving plant nutritional and phytochemical quality through beneficial plant-microbe interactions. These results provide practical evidence supporting the adoption of environmentally friendly substrates and cultivation practices, thus contributing significantly toward sustainable intensive vegetable production systems. Full article

Phytopythium vexans is a plant pathogen responsible for a variety of destructive diseases in crops worldwide. This includes patch canker, damping-off, root, and crown rots in economically important crops, such as apple, pear, grapevine, citrus, avocado, and kiwi. The pathogen has a global distribution, and a recent report confirmed its presence in southern Ontario, Canada. This study presents the first genome sequencing, assembly, and annotation of the Canadian P. vexans strain SS21. To explore how variation in secreted protein repertoires may relate to infection strategies and host adaptation, we compared the predicted secretome of SS21 with reference strains from Iran (CBS 119.80) and China (HF1). The analysis revealed that HF1 harbors a larger set of CAZymes, sterol-binding proteins, and predicted effectors, which may suggest broader adaptive potential. In contrast, strain SS21 appears to have adapted to a niche-specific strategy, with fewer necrosis-inducing proteins, glucanase inhibitors, and effectors, possibly indicating adaptation to specific hosts or ecological conditions. Comparative genome data highlight distinct evolutionary trajectories that may have shaped each strain’s infection strategy, with SS21 potentially serving as a robust additional reference for future studies on P. vexans biology and host interactions. While this analysis identifies key candidate effectors, gene expression studies are required to validate their functional roles in infection and host manipulation. Full article

Citrus peel, a significant by-product of fruit processing, represents a rich source of carotenoids with strong antioxidant and health-promoting properties. The present study evaluated two green extraction techniques, cloud point extraction (CPE) and supramolecular solvent (SUPRAS)-based extraction, for carotenoids recovered from citron, orange, and tangerine peels. Whereas SUPRAS methods rely on a supramolecular solvent made of water, ethanol, and octanoic acid, CPE methods use surfactants and water, and both show a high potential to extract lipophilic components. CPE demonstrated superior efficiency in extracting total carotenoids and enhancing antioxidant activity, with orange peel extracts showing the highest concentrations. CPE and SUPRAS extracts were subsequently encapsulated using freeze-drying with chickpea protein isolate, achieving high encapsulation efficiencies (82.40–88.97%). The use of encapsulation technology is an effective strategy to protect carotenoids from environmental stressors. Color, morphological, and FTIR analyses confirmed the successful encapsulation and retention of carotenoids. Environmental impact was assessed using the EcoScale tool, revealing excellent sustainability for CPE (92 points) and satisfactory performance for SUPRAS-based extraction (70 points). The use of Generally Recognized As Safe (GRAS) solvents and plant-derived encapsulation materials makes this method highly suitable for clean-label product development across the food, cosmetic, and nutraceutical industries. In summary, the results point to a practical and sustainable approach to citrus waste valorization into valuable, health-promoting ingredients—supporting both circular economy goals and eco-friendly innovation. Full article