Investigation the Efficiency of Arbuscular Mycorrhizal Fungi on Physiological Indices of Micropropagated Pear Rootstock (Pyrodwarf) under Drought Stress

Micropropagation is a method for mass and rapid proliferation of plants on tissue culture media. Low survival and poor growth of micropropagated seedling after transplanting is one of the main disadvantages of this technique in many plants. The success of this method can be increased by using biological agents such as arbuscular mycorrhizal fungi. The experiment was conducted to evaluate the efficiency of arbuscular mycorrhizal fungi to improve physiological indices and osmotic regulators content of micropropagated pear rootstock (Pyrodwarf) under drought stress. Factorial experiment was performed in a completely randomized design with two factors (two mycorrhizal and three drought stress level). Experiment was conducted in three replications under greenhouse conditions. Drought stress continued for two months. Results of analysis of variance showed that mycorrhizal symbiosis significantly increased physiological parameters and decreased osmotic regulators at all levels of drought stress. Mycorrhizal colonization percentage determined as 84, 81.66 and 72%, in low, medium and severe drought stresses levels, respectively. Mycorrhizal application significantly increased physiological indices such as Fv/Fm, photosynthetic efficiency index, SPAD index, and the content of chlorophyll b, cartenoid and total chlorophyll in mycorrhizal treatments compared to control (no mycorrhizal plants) and decreased proline and soluble sugars content. Overall, the results of this experiment showed that rootstocks obtained from tissue culture treated with arbuscular mycorrhizal fungi were more adapted to natural conditions and drought stress.