The effect of arbuscular mycorrhizae on Verticillium wilt of pistachio rootstocks Ahmad Aghaei and Badami Zarand: growth, nutritional and biochemical characteristics

Verticillium wilt is one of the important diseases that causes economic damage to pistachio trees. Arbuscular mycorrhizae in addition to improvement of plant growth, can increase tolerance to plant pathogens. In this research, the effect of mixture of three species of arbuscular mycorrhizal fungi, Funneliformis mosseae, Rhizophagus irregularis and Claroideoglomus etunicatum was evaluated on Verticillium wilt of pistachio rootstocks Ahmad Aghaei and Badami Zarand (susceptible and resistant to Verticillium dahliae, respectively). Arbuscular mycorrhizae (AM) inoculation was done at the time of sowing pistachio seeds and pathogen (Vd) inoculated after 52 days using amended inoculum on sand-barley flour-distilled water substrate. The experiment was performed as factorial in completely randomized design with 5 replications in greenhouse conditions. The results showed that the inoculation of AM increases shoot and root dry weight, stem height and diameter, leaf area, concentration of nutrients, proline, soluble sugars, chlorophyll comparison with the control and inoculated plants with the pathogen. In AM+Vd treatment, the presence of the pathogen only in Ahmad Aghaei rootstock caused a decrease in the colonization percentage of arbuscular mycorrhizal fungi comparison with the AM treatment. At the end of the experiment, the pathogenicity index in the Vd treatment was 3.9 and 1.9 in Ahmad Aghaei and Badami Zarand rootstocks respectively but in the AM+Vd treatment it reached to 3.6 and 1.1, which showed a significant decrease in disease severity. It is concluded that inoculation of AM by improving the growth, nutritional and biochemical characteristics can increase resistance of pistachio seedlings to Verticillium wilt.