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    Bulb yield, macromineral and phytochemical contents of garlic varieties grown with phosphorus fertilization in calcareous soil
    (Maximum Academic Press, 2024) Al-Karaki, Ghazi; Othman, Yahia; Altuntas, Ozlem
    The objectives of this study were to investigate the effects of phosphorus (P) fertilizer application on bulb yield, macromineral and phytochemical contents of two garlic ( Allium sativum) varieties 'Balady' and 'Northern White' grown in calcareous soil under field conditions in north Jordan. Three P fertilizer rates were applied [0 (control; P1), 43.6 (P2) and 87.2 (P3) Kg P ha-1 added as super phosphate]. When compared to P1 (control), application of Pat P3 rate increased bulb yield by 49% and 43%, mean bulb weight by 34% and 27% and cloves number per bulb by 35% and 29% in 'Balady' and 'Northern White' varieties, respectively. The total phenols and flavonoids contents and antioxidant activity were significantly higher in cloves of both garlic varieties at P2 rate than at P1 and P3 rates. However, clove flavonoids and allicin contents and antioxidant activity were significantly higher in 'Balady' than 'Northern White' variety at P2 rate only. For mineral contents, P was found to be highest in cloves of both garlic varieties at the P3 rate, while N and Ca contents were highest at the P2 rate. Cloves of 'Balady' variety had higher P content than cloves of 'Northern White' variety at medium (P2) and high (P3) P rates, while Ca contents were found in 'Northern White' than the 'Balady' variety at medium P (P2) rates. Results of this study suggest that the bulb yield and nutritional quality of garlic differed with different rates of applied P fertilization and selection of variety/cultivar under calcareous soil conditions.
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    Effects of mycorrhiza and silicon on the alleviation of salt damage in salt-sensitive and salt-tolerant pepper genotypes
    (Polish Society Magnesium Research, 2025) Altuntas, Ozlem; Dasgan, Hayriye Yildiz; Akhoundnejad, Yelderem; Kusvuran, Sebnem; Yanardag, Ibrahim Halil
    Salinity is a detrimental abiotic stress that occurs in arid and semi-arid environmental conditions. Salinity adversely affects the growth, yield, and quality of plants. Some plants are sensitive to salt stress, while others are more resistant owing to the tolerance mechanisms induced by physiological, biochemical, and molecular responses. The present study was conducted to investigate the effects of mycorrhizal colonization (Glomus clarum) and silicon (Si) under different salinity levels on the activity of antioxidant enzymes, such as super oxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione oxidase (GPX) and lipid peroxidation (MDA), of salinity sensitive (cv. Demre) and tolerant (cv. Karaisali) pepper cultivars. Three diffe-rent salt doses (0 mM NaCl, 75 mM NaCl, 150 mM NaCl), with AM and 2 mM K2SiO3, were applied into 4-L vermiculite-containing pots with pepper plants. The antioxidant enzyme activities increased following the increasing salt doses. All antioxidant enzymes were observed to display differences in their activity in the two pepper genotypes that differed in salt sensitivity. Catalase, ascorbate peroxidase, and glutathione reductase activities were higher in the salt-sensitive pepper genotype. Si and mycorrhiza treatment improved the defense mechanisms in peppers, and attenuated the oxidative damage in cellular functional molecules caused by the overproduction of reactive oxygen species (ROS) under salt stress. Therefore, mycorrhiza and silicon applications, resulting in increased salt tolerance, can be used in areas with salinity problems.
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    Enhancing plant growth, nutrient uptake, and stress resilience in melon through plant growth-promoting rhizobacteria: a two-year comprehensive study
    (Taylor & Francis Inc, 2026) Altuntas, Ozlem; Kutsal, Ibrahim Kutalmis
    Global climate change and increasing water scarcity pose significant threats to melon production, particularly in semi-arid regions where drought stress severely limits plant growth and yield. To address these challenges through sustainable microbial interventions, this two-year field study evaluated the effects of different Plant Growth-Promoting Rhizobacteria (PGPR), including Bacillus subtilis, Bacillus megaterium, Enterococcus spp., and their consortium, on plant growth, yield, and leaf nutrient composition of melon (Cucumis melo L. cv. K & imath;rka & gbreve;a & ccedil; 637) under irrigated and non-irrigated conditions. PGPR applications generally improved vegetative growth parameters, such as stem diameter, main stem length, and leaf number, compared with the control, with Bacillus subtilis consistently showing the most pronounced effects across both growing seasons. Under non-irrigated conditions, Enterococcus spp. application resulted in a marked increase in plant fresh weight compared with the control. Although total fruit yield was not significantly affected by PGPR treatments, leaf nutrient analysis revealed that Bacillus subtilis significantly enhanced magnesium (Mg) and iron (Fe) contents under both irrigation regimes. These findings indicate that PGPR, particularly Bacillus subtilis, can improve vegetative growth and nutrient uptake of melon plants and contribute to alleviating the adverse effects of drought stress, highlighting their potential role in sustainable melon production under water-limited conditions.