بیماری پوسیدگی فوزاریومی طوقه و ریشه گلرنگ در ایران

Among the oilseed plants, safflower (Carthamus tinctorius L.) has a special place for production in climate change conditions. One of the main problems of safflower cultivation is root and crown rots caused by fungi. During sampling from the safflower fields Kose variety in Isfahan province (Kashan and Shahreza), symptoms of root and crown rot were observed. After culturing infected tissues، fungal isolates were isolated from the rotten root and crown .Fungal clony grew 82 mm on the PDA culture medium in temperature alternating conditions of 25 degrees Celsius (day) and 20 degrees Celsius (night) and light alternating conditions for ten days and. The fungus produces white aerial mycelium. Colony of the fungus is purple and can be seen as pale purple from the bottom surface of the Petri dish. This isolate produces green sporodochiums on CLA medium under NUV light. On CLA, it produces hyaline macroconidia with three to four walls with a size of 2.5-3.2 × 10-14.2 micrometers. spherical chlamydospores are formed in large numbers as singly, in pairs or in chains, one- or two-celled ovoid microconidia with a size of 0.8-2.1 × 2.8-4.3 micrometers formed in chains (2-8 numbers), or in false heads. Also, short monophialids with the size of 1.8-2.8 × 11.0-17.4 micrometers and polyphialids were observed. The fungal was identified as Fusarium nygami which is separated from other species of Fusarium by having unique morphological characteristics such as microconidium chain formation, short monophialid and polyphialid. In order to confirm morphological identification, after DNA extraction, ITS and TEF regions were amplified and sequenced. Based on the results obtained from morphological characteristics and analysis of TEF and ITS regions, the fungal isolates were identified as F.nygami. To carry out pathogenicity test, sterile wheat seeds inculated with ten mycelial discs of the fungal isolate, and kept for two weeks at a temperature of 25 degrees Celsius. After scratching of crown، wheat seeds were inoculated to safflower plant in stage 6-4 leaves. The fungal species was re-isolated from the rotten root and Koch's principles were proved. To the best of our knowledge, this is the first report of root and crown rot of safflower by F. nygami in the world.