Study of Some Indices for Freezing Damage in Shoot Tissues of Pomegranate Trees

Winter freezing injury is one of the main problems for pomegranate production in Iran. Therefore evaluation of cultivars and different methods to overcome freezing injury is important. For this reason, it is necessary to find appropriate and reliable indices for evaluation of freezing damage in pomegranate trees. In present study cutting survival percentage, relative electrolyte leakage (EL), relative phenolic leakage and tissue coloring by tetrazolium chloride (TCC) indices were used for comparison of thin or thick of one or two year-old pomegranate shoots in freezing condition (-10, -15 and -20 oC). All evaluation indices except TCC showed the least freezing injury observed in one year-old thick shoots (LT50= -15.4 oC). These shoots had the maximum amount of soluble sugars and proline content. However, there were no difference in relation to water content between on year-old thich shoots and other shoots. Cutting survival percentage criteria that is more reliable index for the damage or tolerance rate, showed the highest correlation (r= -98%) with EL compared to other indices. EL measurement is easier and faster for evaluation than the survival percentage of cuttings, so this method detected to be the most appropriate index for evaluation of freezing injury in pomegranate winter shoots in lab condition.