The effect of arbuscular mycorrhizas, Trichoderma harzianum and their combination on Phytophthora root rot of pistachio seedlings cv. Momtaz: growth, nutritional and biochemical characteristics

Using biocontrol agents is one of the methods to reduce mortality of Phytophthora root rot in pistachio orchards. In the present study, the effect of arbuscular mycorrhizal fungi (AM) (mixture of three species), Trichoderma harzianum (Th) and their combination (AM+Th) were evaluated on Phytophthora root rot caused by Phytophthora drechsleri (Pd) in pistachio seedlings cv. Momtaz. Arbuscular mycorrhizal fungi, Th and their combination were inoculated at the time of sowing pistachio seeds, but the pathogen was inoculated two months later. The results showed that AM, Th and AM+Th treatments and their interaction with Pd significantly increased growth, nutritional and biochemical characteristics of seedlings compared to the control and Pd treatment. The highest increase was observed in AM+Th and AM+Th+Pd treatments. At the end of the experiment, the mortality of pistachio seedlings was significantly reduced from 92% in Pd treatment and reached to 67, 67 and 50% in AM+Pd, Th+Pd and AM+Th+Pd treatments, respectively. It is concluded that inoculation of AM, Th and especially their combination improved the growth, nutritional and biochemical characteristics which can lead to biological control of Phytophthora root rot of pistachio seedlings.