Abstract Safflower plant (Carthamus tinctorius L.), a member of the Asteraceae family, is an annual plant and is compatible with the climatic conditions of the country, which has a special rank among oilseeds. The desirable characteristics of this plant are high adaptability, cold tolerance, low water requirement, and relative resistance to drought due to having deep roots, relative tolerance to salinity and high quality of its oil. The most important production area in Iran is the Isfahan province, the highest cultivation area in Isfahan province is belong to Soffe and Kose varieties. One of the main problems of safflower cultivation is crown and root rot due to fungal attack, which ultimately reduces crop yield. Determining the causal agent species in recent years has shown that these pathogens are changing due to climate changes, so to determine the pathogens causing safflower root and crown rot and reaction of safflower cultivars and inter-specific derived RIL (recombinant inbreed pure line) to fusarium root rot , sampling was performed from August 2020 to September 2021 from infected safflower fields in Isfahan province including Borkhar, Mobarakeh, Ardestan, and Harand counties .Studies have shown that Fusarium solani is the cause of the disease. In order to molecularly confirm the isolated species, ITS5 . ITS4 primer pair was used. Amplification and sequencing showed that the identified species were significantly similar to the sequences of similar species in the genome database. Pathogenicity test in laboratory and greenhouse conditions proved the pathogenicity of the identified isolates and Ar2 isolate with more pathogenicity was selected to continue the research. Fifty six safflower genotypes were eva‎luated for their response to Fusarium wilt in a completely randomized block design with three replications in greenhouse conditions. Artificial inoculation in the greenhouse was done by placing wheat seeds containing fungal mass next to the crown of 4 - 6 leaf seedlings. After two months, the response was assessed by measuring traits such as mortality rate, length of necrosis zone in roots, number of viable plants, dry root weight, dry weight of aerial area, stem height and stem diameter. The results showed that there is a high negative correlation between the mean necrosis length on the root and the number of live plants in the greenhouse. Based on the cluster analysis diagram, genotypes were divided into 5 groups (resistant, relatively resistant, tolerant, sensitive, relatively sensitive). The most resistant genotypes to the disease are Padideh, O, Golmehr, Po84, P, Po114 and Palast37 with mean necrosis length of 1.13, 1.53, 2, 2.13, 2.13. , 2.3, 2.93 mm and mean death percentage was 6.67, 13.33, 6.67, 13.33, 6.67, 13.33, 6.67. Koseh genotypes, To179, Tp1, To142, To158 with mean necrosis length of 13.1, 12.5, 12.43, 11.83, 11.73 mm and mean death percentage 60, 60, 66.67, 66.67, 66.67 were eva‎luated as susceptible genotypes. Since the wild species of C. palaestinus (P) and some genotypes resulting from its interspecies had the highest survival rate and the lowest necrosis length and mortality rate and on the other hand, this species is the most similar in terms of agronomic traits to the domestic species, the use of this species and the lines resulting from its interspecies to create disease-resistant cultivars could be recommended.

بهرام شريف نبي

محمدمهدي مجيدي

قدرت اله سعيدي ، امير مساح