The Study of Spring Frost Resistance of Some commercial Damghan Pistachio (PISTACIA VERA) Cultivars

Pistachio (pistacia vera L) is one of the strategic products of our country and after oil ‏this product has devoted the most amount of exporting to itself. Considering the chilling injury of pistachio it is an endangered product. Determining the critical temperatures at the time of happening, the damage has helped the use of on time and suitable ways for preventing the happening ‏damage and it can also be used to estimate the amount of damage of the product. This damage is resulted from the decreasing of temperature in the early spring which sometimes causes considerable. damage for this reason this research was carried out in Dameghan Azad university during 2007-2008. This experiment was done in a factorial form with a completely randomized block design with two factors of type cultivar with three kinds of pistachio cultivar including Abasali, Shahpasand and Khanjarie. The factor of temperature was with 5 levels of +2,0,-2,-4,-6 degree centigrade. The experiment was done in three growth of productive parts including: swallowed bud, bloomed bud and the new formed fruit nuts. Samples were put in a freezing chamber (low-temperature incubator) in which temperature was decreased with a rate of 2oC per hour. At each thermal level, some samples were taken out and injury was studied. The results showed that the most sensitive stage to frost was bloomed bud and The most damage in to the frost was in the temperatures of -6 degree centigrade. The results showed that Abasali cultivar was more resistance cultivar and the Shahpasand was more sensitive one to spring frost. The Khanjari cultivar was semi resistance cultivar to spring frost.