Physiological and biochemical responses of 10 commercial Iranian pistachio cultivars to freezing

This study was undertaken to compare freezing tolerance of 10 commercial Iranian pistachio cultivars in January and March, and to study the relationship between freezing tolerance and changes in the concentration of soluble carbohydrates, total soluble proteins, proline, phenolic compounds, malondialdehyde (MDA), hydrogen peroxide (H2O2), and water content of buds in both sampling stages. After subject to six different freeze-temperature tests (-9, -13, -17, -21, -25, and - 29 degrees C), bud LT(50)values were evaluated using the measurement of electrolyte leakage and bud browning. In January, 'Chrokeh,' 'Shahpasand', and 'Rezaee' showed the highest freezing tolerance, whereas 'Kaleh Ghouchi' was the least hardy cultivar. Freezing tolerance of all cultivars lessened slightly in March. In this period, 'Sefid Pesteh,' 'Shahpasand,' 'Abbas Ali,' 'Kaleh Ghouchi,' and 'Fandoghi' showed the least freezing tolerance, while 'Rezaee,' 'Momtaz,' and 'Chrokeh' were the highest hardy cultivars. There were significant differences in all the characteristics mentioned above among pistachio cultivars in both sampling dates. Negative correlations were observed between LT(50)values with proline, phenolic compounds, soluble carbohydrates, and total soluble proteins. Also, there was a positive correlation between LT(50)values with the concentration of MDA and H(2)O(2)on both dates and with bud water content in March. These results indicated osmoregulants are valuable indices to screen freezing tolerance in pistachio cultivars.