تاثیر قارچ‏های میکوریز آربوسکولار بر تحمل ارقام پسته به بیماری پوسیدگی آرمیلاریایی ریشه و طوقه

Armillaria root and crown rot is one of the most important diseases of pistachio trees, which can cause widespread death of trees in orchards. Control of the disease is difficult and costly due to the nature of the causal agent and late diagnosis of disease symptoms. Arbuscular mycorrhizal fungi (AMF) as one of the most important biocontrol agents can increase the plants tolerance the diseases. In this research, the effect of inoculation with the mixture of Funneliformis mosseae, Rhizophagus irregularis and Claroideoglomus etunicatum was evaluated on Armillaria root and crown rot in two pistachio cultivars (Momtaz and Badami-Zarand). The propagules of Armillaria mellea (Arm) was propagated on 2-cm pieces of apple tree branches that were colonized with the pathogen for 6 months. Pistachio seeds were sown in pots containing 7% (w/w) of arbuscular mycorrhizal fungi propagules (30 propagules per gram of each species) and after two months, pathogen was inoculated with two pieces of colonized shoots for each seedling. The experiment was conducted as factorial in completely randomized design with five replications in the greenhouse. The results showed that inoculation with AMF in both pistachio cultivars can increase shoot and root dry weight, stem height and diameter, leaf area, concentration of nutrients, proline, soluble sugars, chlorophylls and chlorophyll index comparison with the control and inoculated plants by the pathogen. The presence of the pathogen did not show a significant effect on AMF colonization in roots of Badami-Zarand cultivar. At the end of the experiment, the mortality of Badami-Zarand seedlings decreased significantly from 60% in the AMF+Arm treatment and reached to 45% in the Arm treatment. Inoculation of the AMF could not reduce the mortality of the Momtaz cultivar seedlings. The activity of antioxidant enzymes and the concentration of phenolic compounds in the roots of Momtaz cultivar and Arm treatment, not only did not show an increase, but also it was significantly less than AMF treatment at the end of the experiment, but in Badami-Zarand cultivar, these indicators temporarily increased in Arm treatment and did not show significant difference with AMF treatment at the end of the experiment. In AMF+Arm treatment, maximum activity of antioxidant enzymes and concentration of phenolic compounds was observed earlier and also maximum activity time was longer in Badami-Zarand in compare to Momtaz cultivar. Overall, the results of this research showed that the presence of arbuscular mycorrhizal fungi in roots can increase the tolerance of pistachio seedlings to Armillaria root and crown rot by improving the vegetative, nutritional, biochemical characteristics and increasing the concentration of phenolic compounds and the activity of antioxidant enzymes.