Detection, disease severity, and pathogenicity of Sydowia polyspora Bref.& Tavel in brutian pine stands of Beyağaç (Denizli)

Sydowia polyspora is a common fungal species living on conifers and often emerges as an epiphyte or endophytic on asymptomatic plants and in seeds. The fungus may become pathogenic under abiotic or biotic stress conditions. It is often associated with current season needle necrosis and shoot dieback on conifer species, especially Abies spp. and Pinus spp. throughout Europe and North America. The aim of this thesis is to investigate the fungal agent associated with needle necrosis and shoot dieback in five different Pinus brutia stands located within the boundaries of the Eskere Forestry Management Directorate affiliated to Denizli Regional Directorate of Forestry, to determine the severity of the disease and to reveal the pathogenicity of this agent in P. brutia seedlings. For this purpose, fungal isolations from symptomatic P. brutia needles and shoots were carried out in 5 different stands and totally 68 fungal isolates were obtained. After performing macroscopic-microscopic morphological characterization studies of the isolates, the sequence information of the ITS gene region of the rDNA was used for molecular characterizations. ITS1-ITS4 primer pairs were used for the amplification of the ITS region. The mean disease severity in the sample areas was between 38% and 62% (mean = 47%). In addition, pathogenicity studies were carried out on 2-year-old P. brutia seedlings of the isolates. Infection frequency in inoculated shoots was determined as 90%. Results of pathogenicity tests and re-isolation of the fungus from symptomatic shoots clearly demonstrated that S. polyspora plays a role in the development of needle necrosis and shoot dieback in P. brutia stands. To the best of our knowledge, this thesis is the first study in Turkey to detect needle necrosis and shoot dieback caused by S. polyspora in P. brutia.