The response of Peach Cultivars Grafted onto GN-15 Rootstocks to Application of Organic Acid under Bicarbonate Stress

The aim of this study was to investigate the effect of organic acid on alleviation of bicarbonate stress in three grafted peach cultivars on GN-15 rootstock. The experiment was performed as a factorial based on a randomized complete block design during 2017-2019. Factors included peach cultivars (Red Haven, Jh. Hale and Barzegar), calcium bicarbonate (0, 7.5 and 15 mM), and a combination of oxalic, malic and citric organic acids (0 and 10 mM). Under bicarbonate stress, proline content, activity of catalase enzymes, superoxide dismutase, guaiacol peroxidase and carbohydrate content increased. The highest amount of chlorophyll (1.65 mg / g) and Fv/Fm (0.79) was observed in Barzegar cultivar under non-stress conditions. Under severe bicarbonate stress (15 mmol) the leaves of Barzegar cultivar were able to maintain a higher relative water content (55.77%) compared to other cultivars. Organic acids improved leaf chlorophyll content, proline accumulation, and increased the activity of antioxidant enzymes (catalase, superoxide dismutase, and glutathione reductase). Also, the application of 10 mM organic acids significantly increased the leaf content of phosphorus, iron, zinc and manganese and reduced the severity of chlorosis due to iron deficiency. Finally, Barzegar was introduced as the most tolerant cultivars to iron-deficiency induced chlorosis.