Determination of root rot causing eukaryote pathogens on deciduous and coniferous seedlings in forest tree nurseries in western Turkey

In this study, occurrence and pathogenicity of root rot causing eukaryote pathogens (fungal and Pythiaceous) in forest tree nurseries in western Turkey were investigated. The causal agents were identified using morphological and molecular techniques. Eukaryote pathogens were tested on the host species where the causal agents were isolated from for their ability to cause disease. Survey studies were conducted in eight representative forest tree nurseries in western Turkey: İzmir-Torbalı, Denizli-Karahasanlı, Muğla-Gökova, Isparta-Eğirdir, Antalya-Elmalı, Eskişehir, Bursa and Adapazarı-Hendek. Symptomatic seedlings (totally 296) and soil samples (totally 105) were transferred to the laboratory and investigated for the presence of agents causing root rot. Fungal species were obtained from roots of the symptomatic seedlings by direct isolations from the roots while Pythiaceous species were obtained from the soil samples by the aid of baiting methods. Isolations yielded 199 fungal and 142 Pythiaceous isolates, which were identified using classical morphological methods and molecular techniques, such as sequencing ITS and other gene regions. The morphological and molecular analyses showed that the fungal species; Fusarium oxypsorum, Fusarium solani, Fusarium verticillioides, Cylindrocarpon destructans, Rhizoctonia solani, Verticillium dahliae and Pestalatiopsis clavispora and the watermolds Pythium aphanidermatum, Pythium intermedium, Pythium irregulare, Pythium ultimum, Phytophthora cactorum, Phytophthora citricola, Phytophthora megasperma and Phytophthora syringae were common in the surveyed nurseries. In addition, coniferous seedlings were more symptomatic compared to the deciduous ones. Pathogenicity tests were performed for selected fungal and Pythiaceous isolates on the host species from where they were isolated. The results showed that all isolates were pathogenic and had an ability to grow in all tested hosts. To our knowledge these are the first findings of fungal and Pythiaceous species causing root rot on coniferous and deciduous forest tree seedlings in western Turkey.