Pathogenicity of the Sydowia polyspora originating from different hosts on Pinus brutia in Türkiye

Background and aims Sydowia polyspora is a significant fungus associated with seasonal needle necrosis, particularly on Abies spp. and Pinus spp. in Europe and North America. Pinus brutia is a species widespread in the Mediterranean basin with high economic and ecological value. This study aimed to determine the susceptibility of P. brutia seedlings in Türkiye to local S. polyspora isolates and to investigate the virulence differences among isolates obtained from different hosts. Methods S. polyspora isolates from various hosts were inoculated into the shoots of two-year-old P. brutia seedlings. The seedlings were monitored in comparison with a control group, and pathogenicity indicators such as lesion length were recorded. Results The results showed that 7 out of 10 tested isolates were pathogenic on P. brutia seedlings and successfully colonized the living heartwood tissue. Isolates from Pinus pinea were found to be pathogenic on P. brutia, and isolates obtained from shoots caused longer lesions in hosts. Additionally, isolates from symptomatic trees exhibited higher virulence compared to those from asymptomatic trees. Isolates from P. brutia exhibited higher virulence compared to isolates from Pinus nigra and P. pinea. Conclusions P. brutia seedlings are highly susceptible to local S. polyspora isolates, posing a potential threat to the region's forest ecosystems. The fungal pathogen was successfully re-isolated from symptomatic tissues, and no symptoms were observed in the control plants.