Effect of Arbuscular Mycorrhizal Fungus and Pseudomonas Fluorescent Bacteria on Osmotic Regulators and Water Relations of Pistachio Seedling cv. dQazvinib under Four Irrigation Regimes

To study the interactive effects of arbuscular mycorrhizal fungus (Glomus mosseae) and Pseudomonas fluorescens (P52 strain) bacteria¡ on osmotic regulators and water relations of pistachio seedling (Pistacia vera cv. ‘Qazvini’) under drought stress¡ a greenhouse experiment was conducted using four levels of drought stress (100% Field capacity (FC) as control and 75¡ 50 and 25% FC) and four levels of biofertilizer (non mycorrhizal and non bacterial plants as control¡ mycorrhizal treatment¡ bacterial treatment and a mixed treatment of both) in a completely randomized design as factorial with four replications. The maximum of root colonization (49.6%)¡ leaf relative water content (64.8%) and proline (10.8 mg l-1) was observed in 25% FC. Water use efficiency increased in 50% FC (0.6 mg ml-1). Drought stress reduced the soluble carbohydrates in leaves (2245.3 mg l-1 in 25% FC). None of treatments had effect on proteins and phenolic compounds. According to the results obtained¡ pistachio plants provide resistance against drought with increase of proline and bacterial treatment increased proline content in 25% FC (13.4 mg l-1). In addition¡ effect of mycorrhizal treatment on leaf relative water content was positive (61.3%). Thus consolidated application of mycorrhizal fungus and Pseudomonas fluorescens bacteria is recommended for increasing drought resistance of pistachio.