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Rice blast disease caused by Pyricularia oryzae is considered one of the most important fungal diseases of rice. Due to the importance of the damage caused by this disease, many efforts have been made to identify the factors affecting its spread and management, and also a number of chemical fungicides have been registered and introduced to control it. The use of chemical fungicides has caused environmental pollution and the possibility of resistance to them, so the achievement of resistant cultivars has always been considered. In this study, the resistance of 109 lines of promising lines of Rice Research Institute of Iran along with two control cultivars (susceptible and resistant) against blast disease was evaluated. In order to evaluate leaf blast, at the end of June, the seeds of each line were planted upland in the rice blast nursery. In order to inoculate the desired lines, blast infected leaves were collected from different areas of Guilan province and placed on the surface of the rice blast nursery. At all stages, the necessary moisture to cause disease was provided by sprinkler irrigation. The disease severity was assessed according to the international standard method with degrees from zero to nine. Seven and 14 lines with degrees 2 and 3 showed resistance to leaf blast disease. Other lines were semi-susceptible to highly susceptible to blast disease. Based on the results of agronomic traits and relevant experiments, three lines TH1, TH2, and TH3, which were sensitive to leaf blast disease, were proposed for panicle blast tests. For this purpose, seedlings were planted in large pots in the greenhouse and inoculated with injection into the neck of the panicle. All three lines were assessed susceptible to panicle blast as degree 5.Key woard: Assessment of resistance, resistant cultivars, leaf blast, panicle blast.
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