Table grape berries are classified as a perishable crop that deteriorates quickly after harvest. The application of melatonin after harvest was found to be effective for retarding senescence and slowing ripening. In the current study, we tested the influence of two melatonin concentrations (50 and 100 µmol) as a postharvest application on quality, bioactive compounds, and enzyme activities of grape berries cv “Crimson” stored at 0 ± 1 °C and 90% relative humidity (RH) for 35 days. Our results indicated that melatonin application extends the shelf-life of berries by reducing weight loss and maintaining total soluble solids (TSS), titratable acidity (TA), berry adherence strength, and firmness. Melatonin treatment also reduced pectin methyl esterase (PME) and polygalactouranase (PG) enzyme activities compared to the control. Moreover, O₂^•− and H₂O₂ rates in berries were reduced by high melatonin concentration. Moreover, peroxidase (POD) and catalase (CAT) enzyme activities were increased by melatonin application. Our findings suggested using melatonin postharvest to increase shelf life and maintain quality attributes during refrigerated storage, which could be advantageous on a large scale.

Producing high-quality table grapes is becoming a challenge in the warmer area of the world due to the global increase in temperature, which negatively affects anthocyanin biosynthesis and other fruit quality attributes. Nanotechnology is a growing field that can be a very useful tool to improve crop productivity and sustainability. The red color is one of the major fruit quality parameters that determine table grape marketability. This study aimed to investigate the role of the zinc element in improving the marketable characteristics of Crimson seedless (Vitis vinifera L.) table grape berries i.e., color, firmness, total soluble solids and sugars; besides its role in activating PAL and SOD enzymatic systems. Additionally, this paper investigated the additive advantages of zinc when applied in nanometric form. Five concentrations of zinc oxide nanoparticles, ZnO NPs (0, 25, 50, 100 and 250 ppm), were compared to zinc oxide in mineral form at a concentration of 250 ppm to investigate their effects on the marketable characteristics of Crimson seedless grape cultivar. The treatments were applied as foliar spray on three-year-old Crimson seedless vines grafted on Richter 110 rootstock grown in one of the major table grape production area in Egypt. The experiment was arranged in completely randomized block design and each vine was sprayed with five letters of the solution. The use of the lowest concentration (25 ppm) of ZnO NPs achieved the highest significant enzyme activity (PAL and SOD). Moreover, the T.S.S, sugars and anthocyanin content in berries increased significantly in association of decreasing acidity. On the other hand, the use of a 50 ppm concentration led to an increase in fruit firmness. Collectively, our data showed that 25 ppm of zinc nanoparticles improved PAL and SOD enzymes activity, improved red coloration in table grape and was more effective than the 250 ppm zinc oxide mineral form.

The control of powdery mildew disease is one of the main objectives in Mango production. Mango production with superior quality is becoming increasingly challenging due to climate change, which may negatively affect all stages of their development. Recently, Nanotechnology is a promising and rapidly evolving field that could be a very useful tool to raise the efficiency of fungicides. The aim of this study was to evaluate the role of sulfur nanoparticles (SNPs) and reducing the incidence of powdery mildew, improving growth performance and productivity of mango cv. Keitt (Mangifera indica L.). Four concentrations of SNPs (0, 100, 300, and 500 ppm) were compared to sulfur microform (bulk) at a concentration of 500 ppm. At a private farm on Cairo Alex Desert Road K78, Egypt, foliar spray treatments were administered to an eight-year-old mango cv. Keitt grafted on Sukari rootstock. The experiment was conducted using a randomized complete block design, with each tree receiving a five-liter spray of the solution. The results suggested that the use of 500 ppm concentration of SNPs led to reducing powdery mildew disease incidence by 8.8% but it negatively affected productivity, as it decreased by 27% compared to the control treatment. Whereas 100 ppm concentration of SNPs led to increasing the productivity by 342% compared to the control treatment, reducing powdery mildew disease incidence in mango was recorded at 14.6%. Furthermore, the TSS and vitamin C increased significantly by 16 Brix and 46.3 mg, respectively, in association with decreasing titratable acidity in fruits. In aggregate, our data demonstrated that 100 ppm and 300 ppm of sulfur nanoparticles was more efficient than 500 ppm of sulfur bulk in improving POD and PPO enzyme activity. It is recommended to add SNPs of 100 ppm as foliar spraying three times at 15-day intervals for alleviating the harmful impact of disease on mango trees by improving the enzyme activity, thereby yield, and fruit quality of mango trees exposed to powdery mildew disease.

The study of morpho-anatomical aspects, metabolic changes of proteins, antioxidant substances, as well as phenolic compounds in embryogenic callus (EC) and degenerative embryogenic callus (DEC) was the aim of the present investigation. Ability to form somatic embryos (SEs) was associated with the softness of the EC, which exhibited a white or creamy color and was composed of isodiametric cells containing dense cytoplasm, conspicuous nuclei and minimal vacuoles with observed mitotic activity. Furthermore, protein, reduced glutathione (GSH) and ascorbic acid (ASC) concentrations and the ratio between ASC and dehydroascorborbic acid (DHA) were increased significantly in the EC in comparison to the DEC. In addition, the phenolic extract of the EC was proved to have higher scavenging activity than the extract from the DEC. A loss of embryogenic competence in the DEC was correlated with the presence of more rigid clumps and such calli had a yellowish to brown color and no cell division could be observed in the cells of such aggregates as the cells had large vacuoles and they have very thick walls. Moreover, these morphological and anatomical observations of the DEC were accompanied by accumulations of the oxidized form of ascorbic acid (DHA), H₂O_2, total soluble phenolic compounds and overaccumulation of naringenin. Alternations in cellular metabolism can affect and regulate the morphogenesis of somatic embryos.

Salt stress is a significant abiotic stress factor that negatively impacts plant growth and productivity. This effects growth and productivity of salt-sensitive crops. One promising approach to improving plants capability to withstand salt stress is the use of plant growth regulators, which have shown great potential in enhancing the ability of plants to withstand stress. Thus, the objective of this study is to provide useful information about the influence of melatonin (MT) or brassinosteroid (BR) spraying on vegetative growth, physiological attributes, and productivity of mango trees under salt stress. A field experiment was conducted on Naomi mango trees irrigated with salty well water. Trees were treated with MT and BR at the concentrations of (0.025 mM, 0.05 mM, and 0.1 mM) each. The design used to establish the experiment was completely random sectors, each treatment consisted of five replicates. Indicated that MT at 0.05 and 0.1 mM and BR at 0.05 mM treatments significantly improved vegetative growth, chlorophyll content, and tree productivity under salinity stress. The treatments also enhanced fruit quality by increasing total soluble solids and reducing acidity. Additionally, the application regulators increased the activity of antioxidant enzymes and proline content. Furthermore, the potassium and calcium content of the leaves increased while sodium and chlorine decreased, contributing to better stress tolerance. In conclusion, the use of melatonin and brassinosteroid mitigates the adverse effects of salinity stress on mango trees, leading to improved growth, productivity, and fruit quality. Since such treatments have increased the trees’ tolerance to salt stress, it is advisable to be applied as an agronomic practice in mango trees grown under salt stress.

Essential oils constituents are receiving growing interest due to their bioactivities. This study focused on some aspects of the essential oil obtained from vetiver plant roots, cultivated in the north of Egypt. It is considered as a promising aromatic crop in Egypt, with numerous advantages which compromise with Egypt's environment and soil problems. The vetiver oil was extracted through hydrodistillation, then, the chemical structure of the essential oil was studied using GC-MS. A total of sixty-three compounds were identified as a result of oil GC- MS analysis. The major compounds were khusimol, Isovalencenol, 2- isopropyl -5- methyl -9- methylene-bicyclo -1- decene (4.4.0), α-vetivol, beta-maalene, vetiselinenol, γ-selinenes, zizanol, khusiol and β-vatirenes. Furthermore, the antioxidant capacity and total phenolic content were also investigated using phosphomolybdenum assay and Folin-Ciocalteu colorimetric assay respectively. The essential oil showed 75.5% of total antioxidant capacity at 0.1 mg/ml (100 ppm) while the total phenolic content was 6.7 mg GAE /g. Lastly, antimicrobial activity was studied using an agar medium assay and agar disc diffusion method. All in vitro tested concentrations of the vetiver essential oil had proved its efficiency against Fusarium oxysporum, Alternaria citri, Rhizoctonia solani, and Erwinia carotovora compared to respective controls.