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

The fungus Sydowia polyspora is frequently associated with current season needle necrosis (CSNN) on conifer species, particularly Abies spp. and Pinus spp., across Europe and North America. Pinus brutia is a species commonly found throughout the Mediterranean basin and holds significant economic and ecological value. This coniferous tree species adapts well to the Mediterranean climate, spreading widely across the region and forming a prominent part of its forest ecosystems. In this study, pathogenicity tests were conducted to determine the susceptibility of P. brutia seedlings in Türkiye to local S. polyspora and to investigate potential differences in virulence among isolates obtained from different hosts. For this purpose, two-year-old seedlings of P. brutia, were inoculated on the shoots with isolates of S. polyspora collected from different hosts of Türkiye. In total, 55 seedlings were inoculated and incubated for 8 weeks at 18–20°C. The study results indicated that 7 out of 10 isolates were pathogenic on P. brutia seedlings and exhibited the ability to grow in living sapwood. P. brutia seedlings used in this study are susceptible to the local S. polyspora. Isolates obtained from Pinus pinea were found to be pathogenic on P. brutia. Additionally, isolates obtained from shoots caused longer lesions on the hosts, while those from symptomatic trees were more virulent than those from non-symptomatic trees. It has been determined that isolates obtained from P. brutia exhibit higher virulence compared to isolates obtained from Pinus nigra and P. pinea. Fungal agent was successfully re-isolated from symptomatic tissues. No symptoms were observed in the control plants.