نوع مقاله : علمی پژوهشی - میوه های گرمسیری و نیمه گرمسیری
عنوان مقاله English
نویسندگان English
Introduction
Cold stress is a major environmental constraint affecting plant growth and productivity, with freezing temperatures (< -7°C) causing considerable damage to olive trees in temperate regions. Several approaches, such as foliar application of biotic and abiotic compounds, are explored to enhance plant tolerance to freezing.
Materials and Methods
This factorial experiment was conducted on potted seedlings of three olive cultivars _ Amigdalolia, Conservolea and Muharram _ at Sari University of Agricultural Sciences and Natural Resources from autumn 2017 to spring 2018. Seedlings were subjected to -10°C in a controlled environment, with foliar treatments consisting of Bacillus subtilis, sucrose, ethanol and potassium silicate. Three replications were performed for each treatment-cultivar combination. Various physiological and biochemical parameters were measured, including ion leakage, total chlorophyll content, proline concentration, soluble carbohydrates, and leaf abscission.
Results and Discussion
A significant interaction between cultivar and foliar treatment was observed for all measured traits (P < 0.01). The highest ion leakage occurred in Conservolea treated with potassium silicate (75.93 %), while the lowest was in Amigdalolia receiving potassium silicate (28.92 %). Sucrose increased total chlorophyll in Conservolea (7.41 mg. g-1 FW), whereas the lowest values were detected in untreated and low-concentration bacterial treatments in Amigdalolia. Ethanol treatment led to the highest proline content in Muharram (0.062 mg. g-1 FW), with the lowest in control and low concentration bacterial treatments in Muharram and Conservolea cultivars. Maximum soluble carbohydrate content was recorded in Muharram with sucrose application (300.66 μg. g-1 of FW); the minimum was observed in untreated Amigdalolia (181.67 μg. g⁻¹ FW). Leaf abscission ranged widely, from 100 % in Conservolea with all treatments to just 12.82 % in Amigdalolia with ethanol. Complete branch dying (100%) was most pronounced in Amigdalolia with high bacterial concentration and in Conservolea under all but control treatments.
Conclusion
Foliar application of antifreeze bacteria, sucrose, ethanol, and potassium silicate exerted cultivar-dependent effects on freezing tolerance in olive. Bacillus subtilis reduced leaf and branch loss in Muharram, but negatively impacted Conservolea and Amigdalolia. Sucrose, ethanol and silicon most effectively minimized damage in Amigdalolia, whereas no consistent protective effect was seen in Moharram and Conservolea. The response to foliar spraying under cold stress was therefore highly genotype-specific.
کلیدواژهها English
