Document Type : Research Paper - Tropical and Subtropical Fruits
Authors
1 Former M.SC. Student
2 Sari Agricultural Sciences and Natural Resources University
Abstract
Introduction: Cold stress is one of the most important environmental factors limiting the production and growth and development of crop plants. Freezing, or the reduction of air temperature below freezing point, is a phenomenon that causes damage and injury to plant organs and agricultural products in some temperate regions during the cold season. Damage caused by freezing occurs in olives at temperatures below -7 degrees Celsius and reduces crop production. There are several methods to increase plant resistance to freezing stress. Foliar spraying with biotic and abiotic compounds that can protect trees before cold stress occurs, are preferred for immediate interventions.
Materials and Methods: This experiment was conducted in autumn and winter of 2017 and spring of 2018 in the refrigerator of Sari University of Agricultural Sciences and Natural Resources on potted olive seedlings of Amigdalolia, Conservolea and Muharram cultivars. This study was conducted as a factorial experiment in a completely randomized design with three replications. The applied temperature was -10 degrees Celsius. The foliar treatments included Bacillus subtilis, sucrose, ethanol and silicon.
Results and Discussion: The results of the experiments showed that the interaction of foliar spraying and cultivar on all measured traits was significant at the probability level of 1 %. The highest amount of ion leakage was observed in the treatment with potassium silicate in the cultivar Conservolea (75.93 %), followed by the treatment with ethanol in the cultivar Conservolea (74.54 %). While the lowest percentage of ion leakage in Amigdalolia cultivar was observed in potassium silicate (28.92 %) and ethanol (32.39 %) treatments, respectively. The highest amount of total chlorophyll in sucrose treatment was observed in Conservolea cultivar (7.41 mg/g fresh weight). The lowest percentage of total chlorophyll in Amigdalolia cultivar was observed in control treatments (1.42 mg/g fresh weight) and bacteria with a concentration of 0.001 (1.6 mg/g fresh weight), respectively. The highest concentration of proline in ethanol treatment was observed in Muharram cultivar (0.062 mg/g fresh weight). The lowest concentration of proline in the control treatment (0.015 mg/g fresh weight) and bacteria with a concentration of 0.002 (0.022 mg/g fresh weight) in Muharram cultivar and ethanol treatment (0.022 mg/g fresh weight) in Conservolea cultivar was observed. The highest amount of total soluble sugars in the sucrose treatment (300.66 μg/g of fresh weight) was observed in Muharram cultivar seedlings. The lowest amount of total soluble sugars was observed in the control treatment of Amygdal cultivar (181.67 μg/g fresh weight). The percentage of leaf abscission was affected by the interaction of effect of cultivar and foliar spraying, so that the highest percentage of leaf abscission in Conservolea cultivar (100 %) while using sucrose, ethanol, potassium silicate and bacteria treatments with a concentration of 0.001 and the lowest percentage of leaf abscission in Amigdalolia cultivar (12.82 %) was observed due to the use of ethanol. The highest percentage of dry branches in Amigdalolia seedlings (100 %) as a result of the use of bacteria with a concentration of 0.002 and in Conservolea cultivar as a result of the use of sucrose, ethanol, potassium silicate, bacteria with a concentration of 0.001 was observed with 100 % drying of the branches. with the control treatment (100 %) did not.
Conclusion: The experimental treatments in this research didn’t have the same effects on olive cultivars and preservation of seedlings. In such a way that the use of antifreeze bacteria in the Muharram cultivar reduced the leaf abscission and the drying of the branches, but it had a negative effect on the seedlings of the Conservolea and Amigdalolia cultivars. On the other hand, the application of sucrose, ethanol and potassium silicate compounds in Amygdal variety reduced the percentage of leaf fall and drying of the main branches, and in Moharram and Conservolea cultivars, it didn’t affect the percentage of leaf abscission and drying of the main branches. In general, foliar spraying of olive cultivars in cold stress conditions did not have similar results and depending on the variety, it had different responses.
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