Effects of Harvesting Time on Fruit Development Process and Oil Content of Selected Iranian and Foreign Olive Cultivars under Subtropical Conditions.

Climate change and rising global average temperatures across the year may strongly affect olive fruits' development process and their oil yield and quality. There is therefore an urgency to take immediate actions to characterize the wide variability of cultivars in order to identify those with a stable response to high temperatures, particularly in areas like the west of Iran, which is characterized by a warm summer continental climate. The objective of this study is to investigate the process of fruit development and oil accumulation in response to high summer temperature conditions in a set of four Iranian olive cultivars (Shengeh, Roughani, Zard Aliabad, and Dezful) in comparison with four foreign olive cultivars (Konservolia, Sevillana, Manzanilla, and Mission) in seven various harvesting times (20 July, 5 and 20 August, 5 and 20 September, 6 and 21 October). The obtained results evidence a significant positive correlation between fruit dry matter and oil content. High temperatures reduced the oil and dry matter accumulation in the second half of the summer, with severe thermal conditions adversely affecting oil synthesis. Paramount variations were observed among the cultivars regarding oil accumulation, dry matter, and pomological attributes. All of them showed the highest oil content at the last harvest. Among all analyzed varieties, Roughani showed the highest tolerance and adaptive capacity to high temperatures as it accumulated the greatest amount of dry matter as well as oil content in all of the harvesting times, demonstrating a positive correlation between these two traits. Although Shengeh showed the lowest oil content on a dry and fresh weight basis at the first harvesting time, this cultivar generally presented higher fruit development attributes than the other cultivars, highlighting that it benefits from a high temperature.

Chitosan-based Schiff base-metal (Fe, Cu, and Zn) complexes mitigate the negative consequences of drought stress on pomegranate fruits.

Drought is one of the major environmental stresses that impairs fruit productivity and quality. The proper management of minerals can, however, assist plant to maintain their growth even under drought incidents, and is considered one of the encouraging approaches to refine the drought tolerance of plants. The beneficial effects of chitosan (CH)-based Schiff base-metal complexes (e.g., CH-Fe, CH-Cu and CH-Zn) in reducing the harmful impacts of different levels of drought stress on the growth and productivity of 'Malase Saveh' pomegranate cultivar were examined. All CH-metal complexes displayed favorable effects on the yield- and growth-related attributes of pomegranate trees cultivated under well-watered and different drought situations, with the best effects were observed with CH-Fe application. Specifically, leaves of CH-Fe-treated pomegranate plants showed higher concentrations of photosynthetic pigments [chlorophyll a (Chl a), Chl b, Chl a+b, and carotenoids by 28.0, 29.5, 28.6 and 85.7%, respectively] and microelements (Fe by 27.3%), along with increased levels of superoxide dismutase (by 35.3%) and ascorbate peroxidase (by 56.0%) enzymatic activities relative to those of CH-Fe-non-treated pomegranate plants under intense drought stress. CH-Fe-treated drought-stressed pomegranate leaves showed high increment of abscisic acid (by 25.1%) and indole-3-acetic acid (by 40.5%) relative to CH-Fe-non-treated pomegranates. The increased contents of total phenolics, ascorbic acid, total anthocyanins, and titratable acidity (by 24.3, 25.8, 9.3 and 30.9%, respectively) in the fruits of CH-Fe-treated drought-stressed pomegranates indicated the advantageousness of CH-Fe on the enhancement of fruit nutritional qualities. Collectively, our results prove the explicit functions of these complexes, particularly CH-Fe, in the control of drought-induced negative effects on pomegranate trees grown in semi-arid and dry areas.

Effect of three water-regimes on morpho-physiological, biochemical and yield responses of local and foreign olive cultivars under field conditions.

BACKGROUND: Drought stress is among the most serious threats jeopardizing the economic yield of crop plants in Iran. In particular, in response to withholding irrigation, the reduction in performance and quality of a precious plant such as the olive tree is remarkable. Therefore, the selection of cultivars that are resistant or tolerant to drought has been recognized as one of the most effective long-term strategies for sustainably alleviating the adverse effects of this stress. In this view, our study evaluated the response of 8 olive cultivars including 4 elite native cultivars (Zard Aliabad, Roughani, Dezful, and Shengeh) and 4 foreign cultivars (Manzanilla, Sevillana, Konservolia, and Mission) to water shortage in the Dallaho Olive Research station of Sarpole-Zahab in Kermanshah province in 2020. Olive trees underwent 3 levels of irrigation treatment including 100% full irrigation (control), 75%, and 50% deficit irrigation. RESULTS: Based on the results, 50% deficit irrigation decreased both growth and pomological traits, but determined the highest dry matter percentage. As the severity of drought stress increased, with an accumulation of sodium and malondialdehyde, an incremental increase in osmolytes was observed, as well as an enhancement of the activity of antioxidant enzymes (peroxidase and catalase). In contrast, full irrigation led to an increase in photosynthetic pigments, calcium, and potassium. Dezful and Konservolia cultivars revealed a significantly higher growth rate, correlated in the former to higher levels of chlorophyll, compatible compounds, total phenolic content, relative water content, potassium to sodium ratio, catalase, and peroxidase activities compared with other cultivars. Konservolia showed the best yield parameters under 75% and 100% irrigation regimes, correlated to higher chlorophyll, potassium, and total phenolic content (in particular at 75% ET). CONCLUSIONS: Generally, the selection of more resilient or tolerant cultivars to sustain water scarcity stress is a widely operative solution to extend rainfed orchards in semi-arid environments. Our study showed that Dezful and Konservolia had the best adaptive mechanisms to cope with the detrimental effects of drought stress.

Exogenous melatonin mitigates salinity-induced damage in olive seedlings by modulating ion homeostasis, antioxidant defense, and phytohormone balance.

Melatonin (MEL) is a ubiquitous molecule with pleiotropic roles in plant adaption to stress. In this study, we investigated the effects of foliar spray of 100 and 200 µM MEL on the biochemical and physiological traits linked with the growth performance of olive seedlings exposed to moderate (45 mM NaCl) and severe (90 mM NaCl) salinity. Both salt stress conditions caused a considerable reduction in leaf relative water content and the contents of photosynthetic pigments (carotenoids, chlorophylls a and b, and total chlorophylls), K+ and Ca+2 , while the contents of Na+ and the activities of antioxidant enzymes increased. In addition, salt-stressed olive seedlings showed high accumulations of hydrogen peroxide (H2 O2 ), malondialdehyde (MDA), and electrolyte leakage (EL), indicating that olive seedlings suffered from salinity-induced oxidative damage. In contrast, MEL application revived the growth of olive seedlings, including shoot height, root length and biomass under salt stress conditions. MEL protected the photosynthetic pigments and decreased the Na+ /K+ ratio under both moderate and severe salt stresses. Furthermore, MEL induced the accumulations of proline, total soluble sugars, glycine betaine, abscisic acid, and indole acetic acid in salt-stressed olive seedlings, which showed a positive correlation with improved leaf water status and biomass. MEL application also increased the activities of catalase, superoxide dismutase, ascorbate peroxidase, and peroxidase in salt-stressed seedlings, resulting in lower levels of H2 O2 , MDA, and EL in these plants. Taken together, MEL mitigates salinity through its roles in various biochemical and physiological processes, thereby representing a promising agent for application in crop protection.