Rice blast disease is the major disease of rice in Iran. To control the disease, resistant varieties and chemical approaches are applicable and useful. Usually, when resistant varieties are under high pressure, the resistance may break down. Chemical methods are highly cost and environmental disturbance. So, it is necessary to develop the strategies which are extend stable resistance, such as induced resistance. Induced resistance can be resulted from some of microorganisms, natural and synthetic combinations. Symbiotic microorganisms with plants can induce resistance. Piriformospora indica is a plant-root-colonizing fungus, which causes induction of systemic resistance against different diseases on roots and shoots. This study was performed to induce the resistance against rice blast ( Magnaporthe oryzae ) with endomycorrhiza fungus ( P. indica ). Rice seedlings were treated with mycorrhiza and spore suspension of pathogen ( M. oryzae ). Sampling was carried out in different times points (0, 24, 48, 72 and 96 hr) post inoculation. Total RNA was extracted from leaf samples and then complementary DNA (cDNA) was constructed, expressions of PR1b, PR4 , PR5 , PR10 , LOX , NPR1 , WRKY62 and WRKY85 genes were evaluated, using quantitative real time PCR technique. In microscopic and molecular studies of plant roots in hydroponic and soil cultures, P. indica was detected. These results suggest stable colonization of fungus in rice root. The rate of tillering increased about 50% in treated plants with P. indica . As well, the number of fertilized spikes and shoot fresh and dry weight increased about 45, 30 and 23 % respectively, in treated plants. Findings of this research revealed the promoting of treated plants growth. The sensitivity evaluation of treated and control plants with M. oryzae , showed treated plants had less disease symptoms. Study of infection type, leaf area infection and number of spots showed significant differences in reduction of symptoms in treated plants versus control. Also, expression amount of PR1b , PR5 , PR10 , LOX , NPR1 and WRKY85 genes increased in treated plants with mycorrhiza versus control plants. Results of this study suggest the active role of mycorrhiza in protection of rice plant against blast disease due to enhanced expression of related genes. Key word : Blast; Endomycorriza; gene; Real-time Q-PCR; Resistance
