Effects of auxins and application methods on root regeneration of Pistacia mutica seedlings

Bench (Pistacia mutica F. & M.) is a native tree of Iran. It can be used as a rootstock for pistachio cultivars due to its adaptibility to severe environmental conditions and resistance to some pests and diseases. The very low percentage seedling survival following transplanting has been a major problem in using this wild species as a rootstock for pistachio cultivars. This study was conducted to test the effects of different concentrations of indolebutyric acid (IBA) and naphthalene acetic acid (NAA) and application methods on root regeneration of transplanted bare-rooted beneh seedlings. IBA at 1000 or 2000 mg 1(-1) regenerated more roots, developed longer roots, increased root fresh and dry weight and increased the survival rate of seedlings more than other treatments. Auxin was more effective in increased root regeneration of beneh seedlings when applied using the root-dip method than as a top spray or drench into the growing media. There was a significant interaction between auxin concentration and method of application so that, in most cases, using 2000 mg 1(-1) IBA by the root dip method enhanced the effect of IBA, while this effect at 500 mg 1(-1) NAA was eliminated or reversed when applied using the drench method. It was concluded that application of IBA at 1000 or 2000 mg 1(-1) by the root-dip method would help the survival of seedlings following transplanting.