Karakaya, AzizGEBREMARIAM, ELFINESH SHIKUR2022-08-112022-08-112015http://hdl.handle.net/20.500.12575/83082This research was carried out with the aim of studying the diversity and pathogenicity of Fusarium species associated with crown rot of wheat in Turkey and screening wheat lines for their reaction to Fusarium culmorum. During summer 2013, samples were collected from 200 fields in the different agro-ecological regions of Turkey. Fungi were isolated from symptomatic crown/stem base tissues. The isolates were identified to species level using morphological and molecular methods. Morphological identification of Fusarium species was based on macro and microconidial morphology, phialide structure, mycelial characteristics, pigmentation on agar and growth rate using keys in Fusarium identification manuals. Molecular identification was carried out by sequencing the translation elongation factor-1 alpha (TEF-1α) gene region using primers ef1 and ef2. A total of 342 isolates representing 17 Fusarium species were isolated. The isolates were identified as F. culmorum, F. pseudograminearum, F. graminearum, F. equiseti, F. acuminatum, F. brachygibbosum, F. hostae, F. redolens, F. avenaceum, F. oxysporum, F. torulosum, F. proliferatum, F. flocciferum, F. solani, F. incarnatum, F. tricinctum, and F. reticulatum. Fusarium equiseti was the most commonly isolated species, accounting for 35.55% of the total Fusarium species isolated. Among the damaging species, F. culmorum was the most predominant species being isolated from 13.29% of sites surveyed while F. pseudograminearum and F. graminearum were isolated only from 0.87% and 0.29% of surveyed sites, respectively. All the 342 isolates belonging to the 17 Fusarium species were tested for pathogenicity on susceptible durum wheat cultivar Kızıltan-91 using agar disc inoculation method. Seven out of the 17 Fusarium species tested for their pathogenicity caused crown rot in different levels of severity. Fusarium culmorum, F. pseudograminearum and F. graminearum caused severe crown rot disease on durum wheat cultivar Kızıltan-91. Fusarium avenaceum and F. hostae were moderately pathogenic. F. acuminatum and F. redolens were weakly pathogenic. On the other hand F. oxysporum, F. equiseti, F. solani, F. incarnatum, F. reticulatum, F. flocciferum, F. tricinctum, F. brachygibbosum, F. torulosum and F. proliferatum were non- pathogenic. The result of aggressiveness test showed that Fusarium culmorum isolates differed in their aggressiveness on the susceptible durum wheat variety Kızıltan-91. The most aggressive Fusarium culmorum isolate Fc2 was used as inoculum to screen 165 spring wheat lines for their reaction. Thirteen percent of the lines tested showed promising and consistently resistant/moderately resistant reaction to Fusarium culmorum.trPatolojidoctoralThesis