Effect of Salicylic Acid on Reduction of Spring Cold Damage on some Cultivars of Vitis vinifera and Vitis riparia

Grape (V. vinifera L.) is one of the most important crops in the world and Iran, and play a major role in the export income. According to World Food Organization statistics, the area under global cultivation has been seven million hectares and Iran ranks seventh in the world with 316,000 hectares. Grape production is about 77.5 million tons and Iran is ninth in the world with production of about 2.5 million tons. Fars province is in the first place with 75,000 hectares of fertile vineyards. Qazvin, Khorasan Razavi, West Azarbaijan, Hamadan and East Azarbaijan provinces are also ranked next. Cold stress is one of the constraints on the cultivation of grapes, so prevention of frost damage is one of the important points in the world's grape areas. This damage could be due to early autumn cold and late spring in the temperate region, such as winter frost of 2007, early autumn frost of 2015 and late spring frost of 2014 and 2017. Protecting plants against the harmful effects of low temperatures in agriculture is considerable. One way to prevent frost damages is using plant growth regulators such as salicylic acid. It seems that salicylic acid plays a role in the resistance to the cold stress, and it probably contributes to the activity of antioxidant enzymes and hydrogen peroxide metabolism, so it reduces cold stress damages and increases the plant tolerance to frost. The role of salicylic acid against cold stress have been reported in various plants such as lemon, pistachio, peach, pomegranate, apricot and walnut. Studies have shown that application of salicylic acid on grape seedlings increased the resistance to thermal stresses by reducing ion leakage and decreased the peroxidation of the cell membranes. Also, SA increased the proline and soluble carbohydrates in Plukenetia volubilis seedlings. In the present study, the effects of salicylic acid was investigated on the reaction of potted seedlings of some grape varieties under the spring frost. Then shoot burn percentage, recovery, ion leakage and peroxidation of membrane lipids of seedlings were investigated after cold application. Therefore, the changes in the amount of some osmotic regulators such as proline, soluble carbohydrates, and antioxidants such as phenolic compounds were evaluated by salicylic acid and cold treatments.

This research was carried out in greenhouse of Department of Horticulture Engineering of College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran, in spring 2017 on two-year potted seedlings. It was carried out in a completely randomized design with three replications to evaluate the effects of salicylic acid on reducing the damage of spring frost in some grape varieties such as Bidaneh Sefid, Perlette and Riparia species. Salicylic acid was sprayed at 0, 0.5 and 1 mM in E-L=11 on two year-old potted. After 24 hours, cold treatment was applied at 0 and -2 °C and normal temperature (as control) for 8 h. Control was in the greenhouse with natural temperature. Potted plants were transferred to the greenhouse and after 72 hours, the burn percentage was calculated. Also, recovery of the seedling was determined 20 days after the cold. Other parameters were measured such as ion leakage, malondialdehyde, soluble carbohydrates, proline and phenolic compounds. Statistical analysis and mean comparison of the results was done by SPSS and LSD test.

According to the results, salicylic acid and cold treatments had significant effects on some characteristics of Vinifera species such as Bidaneh Sefid, Perlette and Riparia species. The results showed that with increasing the cold stress to -2 °C, the burned shoot percentage was increased and the grown buds percentage was decreased compared to control, and electrolytic leakage and malondialdehyde were increased at same temperature. Salicylic acid 1 mM reduced the damage to shoots and increased the recovery of seedlings. The lowest amount of electrolytic leakage and malondialdehyde were observed in 1 mM salicylic acid treated seedlings compared to non-treated. According to the results, application 1mM salicylic acid increased osmotic regulators and antioxidants such as proline, solution carbohydrates and phenolic compounds. There was a significant difference between Vinifera and Riparya species at -2 °C in some parameters such as burned shoot, recovery, ion leakage and malondialdehyde. Also, there were significant differences between Bidaneh Sefid, Perlette and Riparia species at -2 °C and 1 mM in proline, solution carbohydrates and phenolic compounds. It has been reported that salicylic acid plays a role of osmotic regulation for the cell and it can reduce the damage of frost by stimulating the hydrolysis of insoluble carbohydrates or proteins and enhancing compounds such as soluble carbohydrates, so it led to reduce the freezing point of the tissue. Increasing in soluble carbohydrates have been reported in grapes and lemon by salicylic acid spraying.

Spring frost has damaging effects on grapevine and can lead to a lot of economic damage to gardeners. Therefore, it can be prevented by some plant regulators such as salicylic acid. The results of the present study showed that the damage caused by cold treatment in control seedlings was more than the plants that were treated with salicylic acid and concentration of 1 mM salicylic acid at 2°C had a positive effect on reduction of morphological damage severity as well as reduction peroxidation of the cell membrane. Cold tolerance of seedlings may be due to the role of salicylic acid in increasing antioxidant substances such as phenolic compounds, as well as in increasing osmotic regulators such as proline and soluble carbohydrates, thereby increasing cell sap concentration and tissue freezing point. This reduced the negative effects of low temperature and reduced cell membrane damage and electrolyte leakage and improved the recovery ability of two-year-old potted seedlings of Bidaneh Sefid, Perlette and Riparia species. So, it can be concluded that among different tested species, Riparia had the lowest percentage of shoot burn and highest recovery ability than the cultivars of Vinifera. Among the genotypes of Vinifera species, Bidaneh Sefid was the most proline and soluble carbohydrate compared to Perlette, indicating a higher adaptation to cold conditions.