Effect of gibberellic acid on seedling growth in two wild species of pistachio

Summary

Beneh (Pistacia mutica F. & M.) and kolkhong (Pistacia khinjuk Stock) are wild species of pistachio which grow naturally with other trees in some parts of Iran. Because of their adaptibility to severe environmental conditions and their resistance to some pests and diseases, they can be used as rootstocks for pistachio cultivars. Poor germination and very low seedling vigour of these two species have been a major problem in using them as rootstocks for pistachio cultivars. In this study gibberellic acid (GA₃), at five concentrations (100, 250, 500, 750 and 1000 mg l²¹), were used during and after stratification to enhance seedling growth. The results showed that GA₃, applied during and after stratification, significantly increased the length, trunk diameter, internode length, leaf area and fresh and dry weight of seedlings of both beneh and kolkhong species. However, application of GA₃ after stratification was more effective on seedling growth of beneh. GA₃ applied at higher concentrations (500 and 750 mg l²¹) increased the rate of growth, but growth malformations were clearly evident in seedlings of kolkhong. GA₃ at 250 mg l²¹ enhanced seedlings growth of kolkhong. It was concluded that application of GA₃ to the seedlings might be a useful method for promoting rapid shoot growth of beneh and kolkhong and reduce the expense of seedling production in glasshouse conditions.